THUMB JOINT BIOMECHANICS OF THE HEALTHY AND ARTHRITIC WHILE PERFORMING COMPLEX MOTIONS By Nicole Arnold A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Mechanical Engineering – Doctor of Philosophy 2023 ABSTRACT Osteoarthritis (OA) is a debilitating musculoskeletal disease that causes degeneration of the joint surfaces. One of the most common areas of OA is at the base of the thumb, or the carpometacarpal (CMC) joint. CMC OA has been cited as a common cause of joint pain and disability which affected range of motion and strength of the hand. Due to loss of hand function, individuals had trouble carrying out activities of daily living which has resulted in a decrease in independence. Furthermore, CMC OA disproportionally affected females more than males, especially over the age of 55. When conservative treatment options failed, surgical intervention was necessary. The most common surgical option, ligament reconstruction with tendon interposition (LRTI), was used to restore function and reduce pain for those that have thumb CMC OA. The effectiveness of surgery was commonly determined via patient questionnaires and clinical measurement devices. Clinical measurement devices to document changes pre- and post-surgery insufficiently captured the three- dimensional (3D) movement of the thumb and lacked accurate representation of isolated thumb forces. Relying on these clinical metrics have led to gaps in research associated with the thumb. For the best treatment options and rehabilitation, data and methods associated with thumb function are needed. The objectives of this work were to: 1) identify the most appropriate mathematical method (Euler or body-fixed floating axis joint coordinate system methods) to obtain 3D motion patterns of the thumb, 2) determine and compare the motion abilities of the thumb in healthy males and females split into two groups (older and younger) and of those with CMC OA at three time points (pre-surgery, 3-months and 6-months post-surgery), and 3) compare isolated thumb force generation in healthy males and females (older and younger) and of those with CMC OA at three time points (pre-surgery, 3-months and 6-months post-surgery). Result highlights of this work are as follows. For goal one, the body-fixed floating axis joint coordinate system method was considered to be the most precise, with fewer disadvantages and was used to determine joint angles of the thumb. For goal two, analysis of motion data suggested there may be premature signs of OA in older healthy females that have not yet experienced pain or visible loss of range of motion. Further, OA individuals appear to have utilized compensatory mechanisms to complete certain motion tasks compared to the healthy groups. For goal three, examination of force data showed that generally, only 50% of CMC OA participants improved at 6-months post-surgery compared to pre-surgery in their force abilities. Further, only one individual reached the level of the older healthy cohort. Overall, this work presents a novel, detailed method for data collection and a complete analysis of thumb motion and force generation for younger healthy individuals, older healthy individuals and those with CMC OA (pre- and post-surgery). This research provides clinicians with in-depth information to encourage individuals to pursue conservative treatment sooner and hand surgeons with new data that provided insights into surgical outcomes and will foster improved treatment plans for those with thumb CMC OA. TABLE OF CONTENTS LIST OF TABLES .......................................................................................................................... v LIST OF FIGURES ..................................................................................................................... viii INTRODUCTION .......................................................................................................................... 1 CHAPTER 1: REVIEW OF LITERATURE .................................................................................. 5 CHAPTER 2: APPROACHES FOR ANALYSIS OF THUMB MOVEMENT .......................... 23 CHAPTER 3: RANGE OF MOTION OF THE THUMB FOR THE HEALTHY AND ARTHRITIC POPULATION ....................................................................................................... 38 CHAPTER 4: ISOLATED THUMB FORCE DATA FOR HEALTHY AND ARTHRITIC PERSONS PRE- AND POST- SURGERY .................................................................................. 67 CONCLUSIONS......................................................................................................................... 105 REFERENCES ........................................................................................................................... 107 iv LIST OF TABLES Table 1. List of average thumb joint angles for Young Healthy individuals ................................ 18 Table 2. List of average thumb joint angles for Older Healthy individuals ................................. 19 Table 3. List of average thumb joint angles for those with thumb CMC OA ............................... 20 Table 4. Clinical Rotations defined by Grood and Suntay and Dabirrahmani described for the right knee. For the knee, the i, I axes (fixed body axis, 𝑒1) point medially, the j, J axes point anteriorly and the k, K (fixed body axis, 𝑒3) point anteriorly. The local coordinate system is defined by {𝑒1, 𝑒2, 𝑒3}={I, 𝑒2, 𝑘} ................................................................................................ 33 Table 5. Individual markers and marker pod locations of the thumb ........................................... 42 Table 6. Marker locations used to create vectors for coordinate systems on each segment ......... 43 Table 7. Clinical Rotations defined by Grood & Suntay and Dabirrahmani & Hogg .................. 50 Table 8. Average VAS and QuickDASH scores for each of the healthy groups. A higher VAS score=more pain and higher QuickDASH score=less function .................................................... 52 Table 9. Average VAS and QuickDASH scores for each of OA participants recorded pre- surgery, 3-months and 6 -months post-surgery. A higher VAS score=more pain and higher QuickDASH score=less function. Only twelve OA females QuickDASH scores were reported at 3-months post-surgery and twelve OA females at 6-months post-surgery as one female at each time point did not complete the full survey. Two OH females QuickDASH scores were also missing due to not completing the full survey .............................................................................. 52 Table 10. Results from isolated flexion-extension for YH and OH groups. The data listed shows the average (standard deviation) in degrees .................................................................................. 53 Table 11. Result findings for isolated flexion-extension of the IP, MCP, and CMC for YH females, YH males, OH females, OH males. The data shows the average (standard deviation) in degrees .......................................................................................................................................... 54 Table 12. Results from isolated flexion-extension at each thumb joint (IP, MCP and CMC) for OA females (n=13) pre-surgery, 3- and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees ........................................................................................ 54 Table 13. Results from isolated flexion-extension at each thumb joint (IP, MCP, and CMC) for OA males (n=2) pre-surgery, 3-and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees ..................................................................................................... 55 Table 14. Summary of YH and OH joint angles for the IP, MCP, and CMC during opposition. Data listed shows the average (standard deviation) in degrees ..................................................... 58 v Table 15. Summary of YH and OH female and male joint angles for the IP, MCP, and CMC as performed during opposition. The data listed shows the average (standard deviation) in degrees .......................................................................................................................................... 59 Table 16. Summary of surgical females (n=13) of the IP, MCP and CMC joint angles as performed during opposition at pre-surgery, 3-months post-surgery and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees .............................................. 60 Table 17. Summary of surgical males (n=2) CMC joint angles as performed during opposition at pre-surgery, 3-months post-surgery and 6-months post-surgery. The data listed is shows the average (standard deviation) in degrees ........................................................................................ 60 Table 18. Average maximum thumb force data (standard deviation) for young healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position ................................................................................................................................. 77 Table 19. Average maximum thumb force data (standard deviation) for young healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position ................................................................................................................................. 77 Table 20. Average maximum thumb force data (standard deviation) for older healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position .......................................................................................................................................... 79 Table 21. Average maximum thumb force data (standard deviation) for older healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 90° wrist position .......................................................................................................................................... 80 Table 22. Average maximum thumb force data (standard deviation) for CMC OA females in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position .......................................................................................................................................... 83 Table 23. Force data of two OA male pre- and post-surgery in the close, far and comfortable locations at the 0° wrist position ................................................................................................... 83 Table 24. Average maximum thumb force data (standard deviation) for CMC OA females in each direction (push and pull) and location (close, far, and comfortable) in the 90° wrist position .......................................................................................................................................... 84 Table 25. Force data of two OA male pre- and post-surgery in the close, far and comfortable locations at a 90° wrist position .................................................................................................... 85 Table 26. Average healthy participant grip strength, tip and key pinch strength (standard deviation) ...................................................................................................................................... 93 vi Table 27. Average grip strength, tip and key pinch strength (standard deviation) for OA males pre-surgery, 3-months, and 6-months post-surgery ...................................................................... 93 vii LIST OF FIGURES Figure 1. Right thumb showing the three joints: interphalangeal (IP), metacarpophalangeal (MCP) and carpometacarpal (CMC). .............................................................................................. 5 Figure 2. From distal to proximal, the bones of the thumb: distal, proximal phalanges, metacarpal and trapezium. ................................................................................................................................. 7 Figure 3. Patient wearing a long opponens thumb spica splint....................................................... 9 Figure 4. Standard clinical goniometer used for joint angle measurements. ................................ 12 Figure 5. The proximal and distal segments of the thumb embedded with their respective coordinate systems. One axis (x) is aligned with the longitudinal axis of the segment, while the other two are mutually orthogonal. ............................................................................................... 25 Figure 6. Proper Euler rotation sequence, Z-Xʹ-Zʺ. ...................................................................... 26 Figure 7. Cardan angle sequence order, 𝑍𝛾𝑌𝛽𝑋𝛼. ....................................................................... 27 Figure 8. The proximal and distal segments embedded with their respective coordinate systems. One axis is closely aligned with the longitudinal axis of the segment. Flexion-Extension occurs about the Y-axis (calculated by angle α). ..................................................................................... 29 Figure 9. The proximal and distal segments embedded with their respective coordinate systems. The green (x/e3) axis points anteriorly, the blue (y/e1) axis points laterally, and the red (z/e2) axis points out of the page. Abduction-Adduction (calculated by angle β) occurs about the z-axis. .. 30 Figure 10. The proximal and distal segments embedded with their respective coordinate systems. The green (x/e3) axis points anteriorly. Internal-External (calculated by γ) occurs about the about the x-axis. ...................................................................................................................................... 31 Figure 11. An example of flexion > 90° resulting in a reflected curve using the Grood and Suntay approach for looking at flexion and extension of the thumb. It is expected to reach 94 degrees. Instead, flexion reaches 90 degrees and starts to reflect back below. ........................................... 32 Figure 12. An example of gimbal lock occurring at a second rotation reaching 180° indicated by the black boxes using the Euler approach. .................................................................................... 34 Figure 13. A set up of two segments with motion capture markers. The moving segment started at approximately 0° (horizontal (A)), flexed to 90° (B) and returned to 0° (A). The plot output of this movement is shown in Figure 14. .......................................................................................... 35 Figure 14. An example of using the body–fixed floating axis coordinate system with one segment relative to another manually moved to 90° of flexion and back to 0°. The Ab/Ad and I/E rotation movements have minimal angle movement as they were only a result of user error. ..... 35 viii Figure 15. An example of a human participant’s thumb values resulting from a different choice of rotation order using different Euler (Cardan) angle sequences. RxRzRy sequence (left) and RzRyRx (right), with the left plot representing the rotation about Y, Z, then X and the right plot showing rotation about X, Y, then Z............................................................................................. 36 Figure 16. Six camera motion capture set-up with testing device on the table where participants sit (A). The testing device with a participant’s forearm and hand resting on the plate at the beginning of testing (B). ............................................................................................................... 41 Figure 17. Marker pods on segments of the thumb, single markers on the sides of the wrist, 2nd and 5th finger MCP joints. ............................................................................................................ 42 Figure 18. The proximal and distal segments of the thumb embedded with their respective coordinate systems. One axis is aligned with the longitudinal axis of the segment, while the other two are mutually orthogonal. ........................................................................................................ 43 Figure 19. Isolated flexion-extension of the thumb starting in a neutral position (A), at maximum flexion (B), and maximum extension (C). .................................................................................... 45 Figure 20. Steps to collect opposition data. A) starting position, B) adduction towards dorsum of hand, C) maximum extension (‘thumbs-up’), D) largest arc prior to oppose to the base of the 5th MCP (palmar abduction), E) completed opposition, F) moving thumb base of the 5th MCP (palmar abduction), E) completed opposition, and F) moving the thumb back to the starting position. ......................................................................................................................................... 46 Figure 21. X-, Y- and Z-axes of the joint coordinate systems on the distal, proximal, and metacarpal phalanges. The X-axis coincides with the fixed body axes e3, while the Y-axis corresponds to the fixed body axis e1. The floating axis, e2, is the cross product between e3 and e1 ............................................................................................................................................. 47 Figure 22. Local coordinate systems of the dorsum of the hand using the 2nd MCP marker. The radius marker and the 2nd MCP marker made up the X-axis, the wrist markers created the Z- axis. The Y-axis was the cross product between the Z- and X- axes which goes into the page. .. 50 Figure 23. The Jamar dynamometer was used to measure hand grip strength. Participants were instructed to use the whole hand to grasp the whole device and squeeze for 2-3 seconds. The average maximum grip strength was recorded. ............................................................................ 71 Figure 24. A) Baseline hydraulic pinch gauge used to measure tip pinch performed with the index finger superiorly and the thumb inferiorly to execute a “pinch” motion squeezing the button as strength was recorded. B) Baseline hydraulic pinch gauge used to measure key pinch performed with the thumb placed superiorly and with the radial middle aspect of index finger underneath the button to squeeze as strength was recorded. The average maximum pinch strength was recorded. ................................................................................................................................ 72 Figure 25. A) 0° wrist position thumb push towards the ground, B) 0° wrist position thumb pull in towards the palm, C) 90° wrist position thumb push towards the ground D) 90° wrist position ix thumb pull in towards the palm E) block system was mounted on the load cell with equally spaced holes where participants placed the peg. ........................................................................... 73 Figure 26. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for younger healthy males (n=13) and females (n=13) in 0° wrist position. ......................................................................................................................................... 76 Figure 27. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for younger healthy males (n=13) and females (n=13) in the 90° wrist position. ......................................................................................................................................... 77 Figure 28. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for older healthy males (n=13) and females (n=13) in 0° wrist position. ... 78 Figure 29. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for older healthy males (n=13) and females (n=13) in the 90° wrist position. ......................................................................................................................................... 80 Figure 30. Average maximum force trials for CMC OA females (n=13) in the close, far and comfortable positions in the 0° wrist position. ............................................................................. 82 Figure 31. Average maximum force trials for CMC OA females (n=13) in the close, far and comfortable positions with 90° wrist position. ............................................................................. 84 Figure 32. Maximum force of two push trials for each CMC OA female (n=13) in the close location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 87 Figure 33. Maximum force of two pull trials for each CMC OA female (n=13) in the close location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 87 Figure 34. Maximum force of two pull trials for each CMC OA female (n=13) in the far location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post- surgery........................................................................................................................................... 88 Figure 35. Maximum force of two push trials for each CMC OA female (n=13) in the far location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post- surgery........................................................................................................................................... 88 Figure 36. Maximum force of two push trials for each CMC OA female (n=13) in the comfortable location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. ..................................................................................................... 89 x Figure 37. Maximum force of two pull trials for each CMC OA female (n=13) in the comfortable location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 89 Figure 38. Maximum force of two push trials for each CMC OA female (n=13) in the close location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 90 Figure 39. Maximum force of two pull trials for each CMC OA female (n=13) in the close location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 90 Figure 40. Maximum force of two push trials for each CMC OA females (n=13) in the far location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 91 Figure 41. Maximum force of two pull trials for each CMC OA females (n=13) in the far location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-mothns post-surgery................................................................................................................................... 91 Figure 42. Maximum force of two push trials for each CMC OA females (n=13) in the comfortable location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. ..................................................................................................... 92 Figure 43. Maximum force of two pull trials for each CMC OA female (n=13) in the comfortable location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery................................................................................................................................... 92 Figure 44. Tip pinch strength for OA females (n=13) pre-surgery, 3-months and 6-months post- surgery........................................................................................................................................... 94 Figure 45. Grip strength for OA females (n=13) pre-surgery, 3-months, and 6-months post- surgery........................................................................................................................................... 94 Figure 46. Key pinch strength for OA females (n=13) pre-surgery, 3-months and 6-months post- surgery........................................................................................................................................... 95 Figure 47. Normalized (by the largest value out of all three time points) grip strength, tip pinch, key pinch, and 0° deg comfortable push and pull performed. These data are for one OA female pre-surgery, 3-months, and 6-months post. Different trends across measurement techniques were noted.. ............................................................................................................................................ 95 xi Figure 48. Average grip strength, tip and key pinch strength, 0° deg comfortable push and pull performed for all OA females (normalized by the largest value out of all three time points) Different trends across measurement techniques were noted. ...................................................... 96 xii INTRODUCTION Osteoarthritis (OA) has been shown to be a debilitating musculoskeletal disease related to the degradation of joint structures [1–4]. Hand OA has been documented as being particularly problematic because it affects numerous joints in the fingers and wrist, leading to limited function [5–8]. Specifically, data has indicated that hand OA affects the distal (DIP) and proximal (PIP) interphalangeal joint of the fingers and the carpometacarpal (CMC) joint of the thumb [5,9–11]. One of the most common sites of hand OA was documented at the base of the thumb [5,9,11–17]. This region, the CMC joint, was also reported as the most painful joint when compared to other joints of the hand [6,18,19]. Pain at the CMC joint has been shown to be exacerbated by performing certain activities, such as opening a jar or food packages. The complete etiology of thumb CMC OA is unclear, and its progression is difficult to assess. However, data suggests that cartilage and synovial fluid, which provide support and cushion to a joint, deteriorate over time, causing laxity in the joint space and are causes for OA formation [4,7,14]. Demographic factors have been shown to affect the prevalence of OA. Risk of developing thumb CMC OA increased with age. It has been reported that people who were 65 years of age had between 2 and 10 times the risk of developing OA as compared to people who were 30, and risk increased thereafter [20]. In addition to age, sex was also a factor in OA prevalence. The majority of individuals affected were postmenopausal women who outnumbered men by six to one [12,21–23]. All people who had OA, regardless of age or sex, experienced some loss in thumb function. Those with hand OA had loss of mobility with increased pain and stiffness, which led to kinematic and kinetic limitations in the hand, including reduced strength, grip and pinch force, and range of motion [3,7,12,24]. 1 Because of the loss of the thumb function resulting from CMC OA, people had difficulties carrying out activities of daily living (ADLs), such as opening and closing containers, picking up and gripping small objects, and lifting heavy items [1,2,7,18,25–27]. Additionally, pain was aggravated by performing ADLs [8,18]. Consequently, the challenges associated with carrying out ADLs with OA secondarily impacted individuals’ work productivity, social functioning, and independence, all of which affected their quality of life [12,18,24]. Conservative treatment options have been utilized to relive pain and improve range of motion. Conservative treatments mitigated the progression and severity of symptoms in patients with early-stage thumb CMC OA [12,23,28–31]. Conservative treatment options included taking non-steroidal anti-inflammatory drugs (NSAIDs), thumb-strengthening and stretching exercises, splinting, modified or reduced activity, and corticosteroid injections [12,23,28–31]. NSAIDs, such as aspirin or ibuprofen, helped reduce pain and inflammation. Research showed those with early- stage thumb OA also benefited from stretching and strengthening exercises [19,24,32] Additionally, splints were worn to immobilize the joint and reduce pain [19,32,33]. While these treatments provided temporary relief, they were not effective for long term or late-stage OA. When conservative options have failed, surgical intervention is considered next. Although, there are several surgical procedures to treat thumb CMC OA, no specific procedure has been identified as superior in comparison to the rest. Most research studies have evaluated the effectiveness of surgical treatment via patient questionnaires and clinical measures, such as goniometry and grip strength [34–37]. 2 To determine how effective surgical treatment is for those with thumb CMC OA, we must understand normative function, as well as function pre- and post- surgery. One challenge in evaluating thumb function is that data are often collected via planar methods. These methods typically involved two-dimensional (2D) measurement tools, such as goniometers, which are straight or flexible, manually operated rulers [38–41]. These means cannot capture three- dimensional (3D) data; and studies have shown they have high inter-rater and high variability [40– 42]. Using a goniometer to measure the angles associated with the digits of the hand is challenging due to the large number of joints being measured in a small space, the complex movements of the thumb, and small lengths of bone [43]. To better understand 3D thumb function, this work determined motion and force abilities in young and older healthy groups without a diagnosis of thumb OA. This work also identified the best mathematical method for obtaining these 3D motion patterns. Finally, this work conducted an analysis of data from those who underwent surgery for thumb CMC OA. This work has been divided into four chapters. Chapter one is a review of the literature discussing the prevalence, statistics, and functional issues corresponding to thumb CMC OA. The treatments used to mitigate thumb CMC OA are described, identifying the most common ones used in addition to the benefits and pitfalls of each type of treatment. The gaps to assess the outcomes of these treatments are presented. One of the goals of this work conducted here will address these gaps; which, in turn, can help create and assess new treatment strategies. Chapter two defines the different methods to understand and analyze the biomechanical movement of the human body. These two methods of analysis included Euler and Grood and 3 Suntay. This chapter presents these approaches: the mathematical application to the thumb, identifying limitations of each, and rational for the choice of method applied to the thumb. Chapter three presents and describes the motion results for the healthy and arthritic groups. Healthy participants (n=52) were split into two groups: younger healthy (YH) (18-39 years) and older healthy (OH) (>40 years) with an equal distribution of males and females (n=13) between each group. OA participants consisted of two groups: females (n=13) and males (n=2) and were tested at three time points: pre-surgery, 3-months, and 6-months post-surgery. Motion results and their clinical utility and impact are presented here. Chapter four describes the isolated thumb force results for both healthy and arthritic groups. Force data were collected in two wrist positions (0° and 90°), two directions of applied force (push and pull), and three self-selected locations labeled ‘close’, ‘far’, and ‘comfortable’. Data sets were compared between YH and OH male and female groups in addition to the OA participants pre- and post-surgery (i.e., the same groupings presented in Chapter 3). 4 CHAPTER 1: REVIEW OF LITERATURE 1.1 Osteoarthritis Definition Osteoarthritis (OA) is a common joint disorder that affects millions of people around the world and 32.5 million adults in the United States [44]. OA has been cited as a common cause of joint pain and disability that affected a person’s everyday life, physically and financially. The overall economic burden associated with OA in the US was estimated at $136 billion annually [44]. Radiographic hand OA or OA diagnosed via images to detect joint space narrowing or cyst formation, have been reported in 67% of women and 55% of men over the age of 55 [44,45]. That Interphalangeal (IP) Metacarpophalangeal (MCP) Carpometacarpal (CMC) Figure 1. Right thumb showing the three (IP), joints: interphalangeal and metacarpophalangeal carpometacarpal (CMC). (MCP) number rises to more than 90% of people above 80 years in age [44,45]. The thumb, primarily the CMC joint (Figure 1), contributes to 50% of upper limb function. It has been reported to be an essential part of performing daily activities and has the second most common site of arthritis in the hand [30,46]. Additionally, as the population continues to age, the number of individuals affected by thumb CMC OA will also increase [20,47,48]. By 2040, research indicated that the number of US adults with doctor-diagnosed arthritis will increase by 49% to 78 million [48]. OA is a prevalent problem that impacts peoples’ lives. 5 1.1.1 Impact on Daily Living Hand and thumb OA have a large impact on individuals’ qualities of life, as they may endure decreased strength, reduced dexterity, and limitations in daily activities. Specifically, decreased thumb CMC range of motion and grip/pinch strength have been shown to affect the ability of a person to grasp and lift objects [12,47,49–52]. Loss of thumb motion results in the inability to complete precise tasks, such as those that require handling small objects, such as utensils or buttoning [10,53,54]. Because the thumb is essential in half of upper limb function, the disability caused by thumb CMC OA generates considerable costs to society, particularly the older adults where they are more likely to become dependent on others and socially isolated [48,51,55]. Additionally, over half of the individuals who primarily use their hands for their occupation have a harder time completing their jobs [13,51]. Decreased strength has prevented individuals from doing strength-based tasks, like lifting household items or opening packages, jars, or bottles [10,12,53]. Other basic tasks such as cooking, general hygiene, and cleaning became more cumbersome and impacted the ability for one to live independently [10]. Thus, an individual may require significant help to complete these tasks or as a result of functional impairments, be unable to care for themselves any longer and need to rely on the assistance of family and friends. 1.1.2 Thumb Anatomy To understand how thumb CMC OA develops over time, it is important to first understand the basic anatomy of the healthy thumb [52,56]. The structure of the thumb includes two phalanges, one metacarpal, and the trapezium (Figure 2). These bones articulate over three joints (from distal to proximal): the interphalangeal (IP) joint, the metacarpophalangeal (MCP) joint, and the carpometacarpal (CMC) joint (Figure 1). The movements of each joint allow for a wide range of motions unique to the thumb. The IP has flexion–extension movement (F/E), the MCP and CMC 6 joint have F/E and abduction–adduction (Ab/Ad) movement with little internal/external movement (I/E) [57,58]. A combination of these movements allows for circumduction (distal end of the thumb scribing a circle) and opposition (a combination of flexion, abduction, and rotation of the thumb to meet various landmarks on the palm and fingers). The CMC joint is a “saddle joint” with the trapezium and metacarpal, having interlocking saddle shapes that oppose one another [57–60]. These unique shapes of the joint allow the thumb to move in multiple directions, which is different when compared to the fingers, which function more like hinge joints. Thus, these complicated motion patterns of the thumb make it a challenging area for researchers to study as the movements are three-dimensional. While understanding the bone anatomy of the thumb is an integral part of analyzing its Distal phalange Proximal phalange Metacarpal Trapezium Figure 2. From distal to proximal, the bones of the thumb: distal, proximal phalanges, and trapezium. metacarpal biomechanics, the soft tissues around the joints are also key to the movement of the thumb. The ligaments, muscles, and tendons form the supporting structure that surrounds the bones and joints of the thumb. The muscles involving movement of the IP, MCP, and CMC joints are the flexor 7 pollicis brevis, extensor pollicis longus, adductor pollicis brevis, flexor pollicis brevis, adductor pollicis, extensor pollicis brevis, opponens pollicis, and abductor pollicis longus. The abductor pollicis longus (APL) inserts on the dorsal radial aspect at the base of the thumb metacarpal, which provides stabilization of the CMC joint [61–63]. In the absence of APL stability, dorsoradial subluxation, or excessive abduction and extension at the base of the metacarpal, occurs. These articulations cause a flexed posture of the thumb metacarpal often called the “swan neck deformity.” It is usually associated with the fingers, but can manifest in the thumb. It is hypothesized that the aspect of the metacarpal adjacent to the APL insertion experiences direct joint compressive loading and surface impingement with opposition and palmar abduction [62]. Another deformity commonly seen due to CMC OA is the “z-deformity,” which is identified by adduction of the CMC joint, hyperextension of the MCP joint, and flexion of the IP joint. There are four main ligaments that provide stability to the CMC joint: the dorsoradial ligament, posterior oblique ligament, anterior oblique (volar beak) beak ligament, and intermetacarpal ligament [64,65]. Several studies have determined that the anterior oblique and dorsoradial ligaments are main stabilizers for the CMC joint [61,65]. The anterior oblique ligament is one of the ligaments responsible for stabilization of the CMC joint, namely during opposition, or positioning of the thumb to oppose to the tips of other digits [59]. Additionally, a population study by Jónsson et al. suggested that primary instability and ligamentous laxity of the thumb MCP joint plays a role in thumb CMC OA [66]. Joint instability and laxity cause excessive shearing forces, which initiate osteoarthritic changes in cartilage in surrounding areas of the joint reducing range of motion [66]. Understanding how anatomy changes with OA can help explain the functional differences that occur. 8 1.2 Treatments for Thumb CMC OA 1.2.1 Conservative treatments There are several treatment options for thumb CMC OA that intend to mitigate progression and severity of symptoms to allow patients to continue their normal activities and improve their quality of life. Splints commonly used for those with thumb OA include prefabricated and/or custom-fabricated orthoses. Several designs are used, but not limited to a long or short opponens thumb spica splint, neoprene thumb orthosis, or custom based thermoplastic orthosis (Figure 3) [19,50,62,67,68]. Figure 3. Patient wearing a long opponens thumb spica splint. Splints are made to immobilize the CMC joint and help reduce inflammation and swelling. Also, splints and NSAIDs are often used in addition to activity modifications such as alternating hand use, using two hands rather than one, performing less forceful pinching or grasping, and avoiding overuse of the affected joint [12,24,69]. Patients also have used assistive devices, such as specialized turning handles or electric jar openers to reduce pain [19,28,29,31,52]. These assistive devices were intended to reduce the load on the thumb CMC joint during tasks [70]. 9 An additional method of conservative treatment included occupational therapy. Exercise regimens have been implemented by an occupational therapist to improve range of motion and increase ligament and muscle strength surrounding the CMC joint [19,71]. Flexibility exercises were designed to maintain the elasticity of the support ligaments and cartilage, while strengthening exercises were designed to increase force generation [31]. Studies have shown that in the early stages of thumb CMC OA a thumb exercise program improved range of motion and strength. A short term follow-up showed no significant improvement in pain [72,73]. Corticosteroid injections into the CMC joint were also used to treat thumb OA. One study reported that there was no statistically significant difference in those treated with an injection to the thumb CMC joint compared to a placebo [74]. Other studies reported that the higher the stage of CMC OA, the less effective the injections were at treating symptoms [17,28,75]. Additionally, some studies indicated that the injections may have contributed to short-term relief, but the long-term effect has not been well documented [31,73]. However, patients must continue to follow exercise, orthotic use, and joint conservation methods to enjoy the benefits of long-term positive outcomes from conservative treatment options. Overall, conservative treatments were used as the first line of treatment [75,76]. 1.2.2 Surgical considerations In many cases surgical treatment may be required. The most commonly reported surgeries were trapezium-sacrificing procedures, such as a complete trapeziectomy and/or implants. A simple trapeziectomy involved removal of the trapezium, but the procedure alone showed postoperative weakness and thumb shortness as a result of subsidence of the thumb metacarpal [17,36]. Implants were a second form of surgery; here a silicone implant replaced the space occupied by the trapezium after a trapezietomy. Results have shown bony erosion, cysts, and breakdown of the implant [23,31,50]. Other surgical options consisted of variations of a 10 trapeziectomy. A Hematoma and Distraction Arthroplasy (HDA) included a trapeziectomy followed by placement of a temporary Kirshner wire to stabilize the thumb metacarpal. This stabilization occurred by placing the wire through the first metacarpal base and securing it to the base of the second metacarpal or trapezoid. Similarly, the cable arthroplasty procedure included complete or partial removal of the trapezium. Next, a cable (also termed a “Mini_TightRope”) into the metacarpals of the thumb and index finger to stabilize the thumb during the healing process. Another common surgical procedure is a trapeziectomy with tendon interposition. This procedure involved removal of the trapezium followed by interposition of a tendon rolled-up to replace the trapezial space. In a similar procedure, a trapeziectomy with ligament reconstruction with tendon interposition (LRTI) used all or part of a tendon to suspend the thumb metacarpal, while the remaining portion of the tendon filled in the trapezial space. A randomized study investigated the outcome measures of a trapeziectomy, trapeziectomy with tendon interposition, and trapeziectomy with ligament reconstruction and tendon interposition with a minimum follow-up of five years (range was five to 18 years). These researchers reported that between the three surgeries there was no difference among the three surgical group; however, the only evaluation conducted was 11 subjective assessment of pain [34]. Therefore, better forms of assessment are necessary to determine changes and improvements in function. 1.3 Measurements of Hand Movement 1.3.1 Clinical Measurements of Motion Over several decades different methods and equipment have been used to analyze motions of the digits, joints, and the whole hand. These methods quantified both 2D and 3D measurements, including goniometry, electromagnetic tracking, imaging, and video-based motion analysis systems. As previously mentioned, the use of goniometers has become the standard for joint angle measurement [41,42,77]. While goniometers have demonstrated ease of use and minimal set up, they only examined static motions with results of low accuracy and poor intra-rater reliability [38,40–42]. Additionally, measurements recorded with goniometers depended on the examiners’ experience and training [41,42,78]. Furthermore, studies have shown that there were discrepancies of measurements reported using goniometers [40,41,43,66,79]. A study that surveyed hand therapists using goniometric instrumentation placement during proximal interphalangeal (PIP) and Figure 4. Standard clinical goniometer used for joint angle measurements. distal interphalangeal (DIP) joint measurements found that they measured up to 13° difference [77]. Although goniometric measurements continue to be the clinical standard, they have not been sufficient to quantify complex and dynamic motions of the thumb. A second method for 12 measurement used electromagnetic tracking. Electromagnetic tracking was used to characterize movements of the hand and wrist [66,80–83]. Imaging also has been used to model the hand to quantify motion of the digits and joints. Common imaging techniques included computed tomography and ultrasound; however, these studies only utilized static images, not dynamic motion, which would be beneficial when capturing complex 3D movements [84–86]. Video-based motion, also known as motion analysis, tracked the 3D movement of reflective markers that were affixed to the body with a set of cameras. Motion analysis has proven to be precise, sensitive, and flexible, making it adaptable to many body and bony segments [42,81,87]. Several studies used a video-based motion analysis system for capturing the kinematic properties of finger and thumb motion [49,87–92]. However, the limitations of motion analysis included occlusion from camera views and marker superimposition. Despite these limitations, motion analysis has proven to be accurate to less than 1 mm and has been a validated method for quantifying 3D joint, hand, and thumb segment movement [81,87,93,94]. In addition to measurement devices, qualitative measures, i.e., questionnaires (e.g., the Australian/Canadian Hand OA Index pain subscale and visual analog scale (VAS) for pain assessment were examples of measures used to assess function pre- and post-treatment of CMC OA. However, these questionnaires were subjective and relied heavily on the reporting by the patient. Sample questions included in questionnaires include ‘On a scale of 0 (no problems) to 4 (extremely difficult) how difficult is it to perform the following tasks: opening a jar, turning faucets on, gripping and turning a doorknob, or peeling/chopping vegetables.’ Or ‘Because of OA, are you limited in your ability to enjoy leisure activities, to do housework, or dressing oneself?’ [18,47,51]. While these questionnaires are helpful in determining what daily tasks patients have trouble with having thumb OA, results do not depict the biomechanical details that impact thumb function. 13 1.3.2 Clinical Measures of Force Mechanical loading (i.e., forces and pressures) transmitted through the joints of the hand has been considered an important risk factor of hand and thumb OA. Devices that have been used to collect strength measurements (i.e., force measurements) of the digits and hand included the dynamometer, pinch gauge, or custom-made devices. These devices measured whole hand grip strength and the contact forces between two digits. Many studies described force generation or load of one or more digits as the force generated by that specific digit(s). While these devices quantified maximum strength required to execute a posture, it did not provide insight into the force required by individual digits to carry out various activities [54]. Studies have generalized force production of the thumb via pinch and grasping postures [57,95–97]. Additionally, studies that measured maximum force generation utilized custom made cylindrical devices (at various diameters) that measured the amount grip strength an individual produced as well as joint angles of the thumb [95–99]. The data reported from researchers with the various techniques previously mentioned did not represent a variety of real-world interactions with everyday objects. Additionally, isolating thumb force generation is lacking. 1.4 Measuring 2D and 3D motions of the hand and thumb 1.4.1 Healthy thumb range of motion data Healthy thumb function requires knowledge of previously reported methods of determining function and the resulting datasets. Function can be quantified by measuring range of motion of the segments and joints in the thumb. Joint angle ranges of motion typically included flexion- extension (F/E), abduction-adduction (AB/AD), internal-external (I/E), rotation, and opposition. As noted previously, various methods have been used to gather healthy thumb data, all with unique challenges [49,66,100–106]. 14 Thumb motion datasets have been used to study factors, such as biological sex and age, on thumb motion. Several studies have reported the average thumb range of motion for healthy younger and older groups as well as a select few for the OA group. A brief summary is provided on the findings of these studies and will be incorporated into comparisons of the data obtained for this dissertation. First, the younger group thumb ranges will be discussed, as shown in Table 1. The reported average IP flexion was between 44° to 96° [49,101,102,107–110] and between 5° to 33° for average IP extension [49,101,102,107]. Average MCP flexion values were reported to be between 42° to 77° [49,101,102,107–110] and between 0° to 58° [49,101,102,107] for average extension. Studies that reported radial and palmar Ab/Ad, only reported whole thumb motion, not of the individual joints [49,103,111,112]. Healthy CMC range of motion values were often reported during opposition and/or circumduction. Average CMC flexion and extension values were reported between 31° to 51° and 48° to 63°, respectively [89,92,107]. Radial abduction of the CMC joint was reported to be between 21° to 63° [89,92,103]. Thumb range of motion for the older healthy population was also studied, summarized in Table 2. The reported average IP flexion and extension was 54° to 66° and 13° to 32°, respectively [49,100]. Average MCP flexion values were reported to be between 47° to 55° and between 0° to 14° for average extension [49,100]. The two studies referenced for IP F/E and MCP F/E used motion capture and goniometry. MCP radial abduction and palmar abduction was reported to be 51° and 47 to 60°, respectively [113]. The reported average CMC flexion and extension ranges was reported as 13° to 44° and 11° to 58°, respectively [83,100,114,115]. The CMC radial abduction was 43° to 71° [83,114,115]. CMC range of palmar Ab/Ad was reported as 25° to 48° 15 [73,114,116]. CMC rotation is reported, however, less frequently than the other motions, as 56° to 57° [86,114]. Multiple studies have obtained average joint angles for those with osteoarthritis. A summary of thumb motions of individuals with thumb CMC OA are listed in Table 3. Reported IP and MCP flexion was 62° to 81° and 51° to 62°, respectively [49,117,118]. IP and MCP extension was 16° to 31° and 13° to 20°, respectively [49,117]. Additionally, radial and palmar Ab/Ad for the IP and MCP has not been well reported. CMC F/E was reported to be 31° to 51° and 31° to 63°, respectively [67,83,89,115]. Average range of CMC radial and palmar abduction has been reported as 31°to 54° and 36°, respectively [83,89]. Additionally CMC palmar adduction ranged between 26° and 33° [118]. However, these studies that reported thumb motion for YH, OH, and arthritic used different methods to collect data: motion capture [49,89,103,117] and goniometry [100– 102,107,108,110,111]. One study used a measurement tool using radiographic images [109], a pollexograph (a large protractor that measures palmar abduction) [111], 3D CT [114], optoelectric systems [92,119], electromagnetic systems [83], and a fluoroscope [115]. Additionally, most studies did not differentiate between males and females of reported joint angle averages [89,107,115,119]. Studies that reported averages during opposition or circumduction varied on what joints were reported or they described the whole motion of the thumb, which averaged angles of all the joints [49,83,103]. While several studies captured the joint ranges of motion of the thumb, the majority have used planar based methods [100,115,116]. Of those that have included 3D motion of the thumb, most have reported standard clinical measurement of the IP and MCP joint, namely, flexion-extension and abduction-adduction. Several issues exist with reported data sets. These issues included joint angles reported, averaged data of males and females, and types of 16 thumb motions reported. An encompassing thumb joint data baseline of YH, OH and arthritic populations is needed to compare between groups. These data will help determine if function has been restored to a normative state post-surgery for CMC OA patients. 17 Table 1. List of average thumb joint angles for Young Healthy individuals Young Healthy (<50 yrs) Joint Movement Angle (deg) Citation IP Flexion 24-96 IP Extension IP Radial Abduction IP Radial Adduction MCP Flexion 5-35 5-88 MCP Extension 0-58 Shaw and Morris 1992, Barmakian 1984, Joseph 1951, Hume 1990, Yoshida 2003, Jenkins 1998, Vocelle 2020, Leitkam 2015, Li 2006, Leitkam 2015, Vocelle 2020, Yoshida 2003, Hume 1990, Barmakian 1984 N/A N/A Li 2006, Leitkam 2015, Jonsson 2007, Vocelle 2020, Jenkins 1998, Yoshida 2003, Hume 1990, Cooney 1981, Joseph 1951, Barmakian 1984, Shaw and Morris 1992, Leitkam 2015, Jonsson 2007, Vocelle 2020, Yoshida 2003, Hume 1990, Cooney 1981, Barmakian 1984, Holzbauer 2021 51 12-33 Li 2006, Jonsson 2007, Cooney 1981 MCP Radial Abduction MCP Radial Adduction MCP Rotation CMC Flexion CMC Extension 18-63 Gehrmann 2010, Barmakian 1984, White 2018 24-61 Barmakian 1984, Gehrmann 2010, Muira 2004, CMC Radial Abduction CMC Radial Adduction 13-22 Li 2006, Cooney 1981 22-51 Gehrmann 2010, Li 2006, White 2018 20-61 Barmakian 1984, Gehrmann 2010, Muira 2004, Goubier 2006, Cooney 1981 White 2018 18 Table 2. List of average thumb joint angles for Older Healthy individuals Older Healthy (>50 yrs) Joint Movement Angle (deg) Citation IP Flexion IP Extension IP Radial Abduction IP Radial Adduction MCP Flexion MCP Extension MCP Radial Abduction MCP Radial Adduction MCP Palmar Abduction MCP I/E Rotation CMC Flexion 54-66 Vocelle 2020, Mruk 1999 13-32 Vocelle 2020, Mruk 1999 N/A N/A 47-55 Vocelle 2020, Mruk 1999 0-14 Vocelle 2020, Mruk 1999 51 Holzbauer 2021 20-23 Holzbauer 2021 47-60 Holzbauer 2021 N/A 13-44 Kimura 2016, Muira 2004, Mruk 1999, Serra Lopez 2021, White 2018 11-58 Serra Lopez 2021, Kimura 2016, Mruk 1999, Muira 43-71 Muira 2004, Kimura 2016, Serra-Lopez 2021, White 2004, White 2018 CMC Extension CMC Radial Abduction CMC Radial Adduction CMC Palmar Abduction CMC Rotation 56-57 Cheema 2006, Kimura 2016 2018 Muira 2004, 2018 25-50 Villafañe 2013, Kuroiwa 2018, Kimura 2016, White 19 Table 3. List of average thumb joint angles for those with thumb CMC OA Angle >40 yrs (deg) 62-81 16-31 Citation Vocelle 2020, Leitkam 2015, Hayashi 2021 Vocelle 2020, Leitkam 2015, Hayashi 2021 N/A Joint Movement IP Flexion IP Extension IP Radial Abduction IP Radial Adduction MCP Flexion MCP Extension MCP Radial Abduction MCP Radial Adduction CMC Flexion CMC Extension CMC Radial Abduction CMC Palmar Abduction CMC Palmar Adduction Thumb Radial Abduction N/A 51-62 13-30 Vocelle 2020, Leitkam 2015, Hamann 2014, Hayashi 2021 Vocelle 2020, Leitkam 2015, Hayashi 2021 N/A N/A 33-44 Hamann 2014, Serra Lopez 2021, Miura 2004 33-50 Gerhmann 2010, Serra Lopez 2021 31-54 Gerhmann, Serra Lopez 2021, Hattori 2016 36 Hattori 2016 26-33 Hattori 2016, Hayashi 2021 36-61 Vocelle 2020, Kjeken 2005, Villafañe 2013 Thumb Palmar Abduction 44 Vocelle 2020 20 1.4.2 Range of motion data while performing ADLs Range of motion has been heavily reported on the hand and fingers, but it is less reported in the thumb. Flexion angles while performing a tip pinch were reported for the IP, MCP, and CMC joints as 36°, 9° to 22°, and 10°, respectively [120–122]. IP, MCP and CMC extension angles were reported to be 34°, 11° to 15°, and 24° , respectively [121]. Average MCP and CMC abduction angles were reported as 16° and 15°, respectively, also for tip pinch [120,121]. During key pinch, IP, MCP, and CMC flexion ranged from 22° to 98°, 20° to 31°, and 4° to 20°, respectively [27,102,120]. Cylindrical grip (diameter=6.3mm) tests reported average IP, MCP and CMC flexion values as 37°, 35°, and 10°, respectively [120]. Additionally, CMC and MCP axial rotation was found to be 33° and 2° for tip pinch, respectively [121]. While these joint angles give information on healthy thumb posture, the positions of the thumb were static and not representative of thumb motion throughout the execution of a task. While some studies only reported stationary joint angles of the thumb during a task, some ADL specific studies reported ROM of the thumb during performance of a task [123–125]. These ADL tasks included typing on a computer keyboard, using a cell phone, turning a key in a door knob, and writing. Average IP and MCP flexion while typing on a computer keyboard were reported to be 18° and 25°, respectively [126]. Average abduction of the MCP while typing was 28° [126]. Joint angles while using a cell phone reported maximum IP, MCP and CMC flexion as 6 to 42°, 6° to 50° and 29°, respectively [66,124]. Johnson et al., reported flexion, abduction, and extension values during cell phone use, but no joints were specified [66]. While writing, the range of thumb IP, MCP and CMC joint flexion was reported as 5° to 118°, up to 10°, and up to 41°, respectively [27]. While several studies have reported ROM of the thumb while preforming ADLs, various methods were used, thus making it difficult to form comparisons across studies. Additionally studies reported joint angle averages across all ADLs, not for individual tasks 21 [53,123]. Furthermore, very few of these studies reported ADL ROM data for those with hand or thumb OA, nor those pre-and post- surgery. Range of motion and joint angles while performing ADLs have not been extensively studied in the thumb due to the complexity of the motions. The majority of studies only considered static postures of the fingers and thumb while they performed a pinch, grasp or grip task (e.g., tip pinch, key pinch, or gripping a circumferential object) [120,121,127]. Several methods were used to report ROM of the thumb while performing ADLs such as goniometry, electrogoniometry, motion capture, or instrumented gloves [27,66,120,121,123,124,126,127]. One study used several ADLs to investigate ROM and joint angles of the thumb and fingers, including (but not limited to) reading, writing, turning on/off a faucet, washing/drying hands, combing hair, eating with utensils, etc [27]. While this is one of the only studies that determined data of the thumb joints of several ADLs, an instrumented glove was used which obstructed tactile sensation, which limited ROM while executing the abovementioned ADLs. Additionally, none of the studies provided ROM and angle data for thumb OA or older healthy populations. Thus, due to lack of data to represent a variety of the healthy population, the arthritic population, and data captured during various tasks; there is a need to expand the literature on these gaps to better understand the impact that osteoarthritis has on the complex motions of the thumb. 22 CHAPTER 2: APPROACHES FOR ANALYSIS OF THUMB MOVEMENT 2.1 Introduction Biomechanical movements of the human body have been described by rigid body kinematics to allow researchers to compare normal function to altered function that may have resulted from injury or disease [49,117,128–130]. Some two-dimensional (2D) approaches for the thumb have been used in clinical settings and some were able to determine differences between normal and altered function. However, these 2D approaches were unable to fully capture all the changes as thumb motion is three dimensional (3D) [38,39,131]. A limited set of studies used motion capture to quantify some aspects of 3D motions associated with the thumb [42,81,87,91]. The joint kinematics of the lower body, such as the hip, knee and ankle, have been studied extensively using 3D techniques [129,132–136]. Kinematics of the upper body, such as the trunk, elbow, and shoulder, have also been studied on a more limited basis [87,119,129,135,137–139]. Two approaches for quantifying thumb motion were considered for this study. The first approach involved the use of an Euler angle sequence to determine thumb segment rotations [140,141]. This approach was frequently used in biomechanical applications [88,97,103,120,142,143]. Researchers have applied Euler angles to lower body segments such as the knee, ankle, and foot [132,144,145], as well as upper body segments like the shoulder, trunk, back, elbow, wrist, hand and digits of the hand [57,84,88,103,143,146,147]. The second approach was developed by Grood and Suntay, which was described by using axes fixed on each of the two bodies and a “floating” axis shared between the bodies [148]. A select number of studies have utilized the method developed by Grood and Suntay (body-fixed floating axis joint coordinate system) for joint motion analysis, but have focused mostly on the lower body segments [146,149–154]. Because of the thumb’s wide range of motions in three dimensions, it is necessary to utilize a 3D approach to quantify its motion. This was especially true of the thumb because it contains one of the most 23 complex joints in the body [18,155–159]. Both approaches determined kinematics of body segments and joints using sequential, specifically ordered rotations, about the axes of one segment’s coordinate system relative to the other. Clinical angles (flexion-extension or F/E, abduction-adduction or Ab/Ad, and internal-external rotations or I/E) have been calculated from these rotations using both methods. However, when using these two approaches for analyzing kinematic data, several questions arose. For example, using Euler angles the choice of rotation order was not clear and varied based on the researcher. Furthermore, when both approaches were applied to the thumb, mathematical issues occurred depending on the motion and segment/joint being analyzed [88,103,120,121,143,146,147,160,161]. Thus, a better understanding of these methods and the challenges associated with them, as they pertain to the thumb was necessary. Therefore, the goal of the work was to apply these two approaches (Euler and Grood and Suntay) to the thumb and identify the limitations of each, and based on the evaluation select the best approach for moving forward. 24 2.2 Descriptions of the Two Analysis Methods 2.2.1 Method 1: Euler Angle Method Euler angles have commonly been used to describe the movement of two rigid bodies connected by a joint. The first body, or the proximal/fixed body segment, contains a coordinate system (X, Y, Z) with coordinates along unit vectors (I, J, K). The second body, or the distal/moving body segment, contains a coordinate system (x, y, z) with coordinates along unit vectors (i, j, k) (Figure 5). The coordinate system on each body segment has one axis parallel to the long axis of the body segment. The other two axes are both mutually orthogonal to the long axis of the body segment. Both segments, moving and fixed, are commonly defined in terms of a third reference, typically a global or laboratory frame of reference. Z Z z Z Figure 5. The proximal and distal segments of the thumb embedded with their respective coordinate systems. One axis (x) is aligned with the longitudinal axis of the segment, while the other two are mutually orthogonal. Using the coordinate systems for each thumb segment, the orientation of the moving segment can be found relative to the fixed segment by three successive rotations. First, the creation of a 3 x 3 directional cosine matrix describing the rotation of the moving frame relative to the fixed must be determined. In Eq. 1, let 𝐴̅ represent a vector (with coordinate positions x, y and z) where it is rotated by a specified angle denoted by rotation matrix, R. After the three completed rotations, 25 the original vector becomes a new vector 𝑎̅ (with new coordinate positions x, y, and z). The rotation matrix, Rij, represents the 3 x 3 directional cosine matrix relating vector 𝑎̅ to 𝐴̅. 𝑎𝑥 𝑎𝑦 𝑎𝑧 [ ]=[ 𝑅11 𝑅12 𝑅13 𝑅21 𝑅22 𝑅23 𝑅31 𝑅32 𝑅33 ] [ 𝐴𝑋 𝐴𝑌 𝐴𝑍 ] = [𝑅] [ 𝐴𝑋 𝐴𝑌 𝐴𝑍 ] Eq 1 The Euler sequence is used to relate the positions of the fixed and moving bodies using three ordered rotations, or three rotation matrices [141]. The order varies within literature; however, order is not commutative and must be specified. The proper Euler angle sequence is a rotation order where the first and third rotations occur about the same axes. An example of a Proper Euler angle rotation sequence is denoted Z-Xʹ-Zʺ (Figure 6). This rotation order was Figure 6. Proper Euler rotation sequence, Z-Xʹ-Zʺ. described in the following way: the coordinate system XYZ was first rotated by an angle 𝛷 about the Z axis, in which the Z-axis stayed the same, i.e. Z=Zʹ, and the new coordinate system becomes XʹYʹZʹ. The second rotation rotated the new coordinate system, XʹYʹZʹ, by an angle of 𝜃 about the Xʹ axis, so that Xʹ= Xʺ. The rotation by angle 𝜃 yielded a new coordinate system, XʺYʺZʺ. Finally, a third rotation of an angle 𝜓 about the Zʺ axis, yielded new coordinate system, where Zʺ=Z‴. The joint angles can then be determined from the entries in the proper Euler rotation matrix, RE ij (Equation 2a) which can represent the joint angles 𝜓, 𝜃, and 𝛷 (F/E, Ab/Ad, I/E rotation) from Equation 2b [141,162]. 26 𝑅𝑖𝑗 𝐸 = 𝑍 𝜓 𝑋𝜃𝑍𝜙 cos 𝜙 cos 𝜓 − sin 𝜙 cos 𝜃 sin 𝜓 sin 𝜓 cos 𝜙 + sin 𝜙 cos 𝜃 cos 𝜓 sin 𝜙 sin 𝜃 sin 𝜙 cos 𝜓 − cos 𝜃 sin 𝜓 cos 𝜙 −sin 𝜙 sin 𝜓 + cos 𝜃 cos 𝜙 cos 𝜓 cos 𝜙 sin 𝜃 ] = [− cos 𝜓 sin 𝜃 −cos 𝜓 sin 𝜃 cos 𝜃 𝜙 = tan−1 ( 𝑅13 𝑅33 ) , 𝜃 = cos−1(𝑅33) , 𝜓 = −tan−1 ( 𝑅31 𝑅32 ) Eq 2a Eq 2b Another way to define a Euler sequence was by rotating about three different axes, instead of having a rotation about a repeated axis. The rotation occurred about three different axes (i.e. x-y- z) is commonly referred to as Cardan angles (Figure 7). Using this rotation order, the coordinate system 𝑥0𝑦0𝑧0 is first rotated by angle 𝛼 about 𝑥0, yielding a new coordinate system 𝑥1𝑦1𝑧1, where 𝑥0 = 𝑥1. The second rotation rotates the new coordinate system, 𝑥1𝑦1𝑧1, by β about 𝑦1, which yields a new coordinate system 𝑥2𝑦2𝑧2, where 𝑦1 = 𝑦2. The final rotation rotates the coordinate system by an angle γ about 𝑧2, where 𝑧2 = 𝑧3, yielding the final coordinate system, 𝑥3𝑦3𝑧3. One example of a directional cosine matrix resulting from a Cardan sequence, RC ij is . Figure 7. Cardan angle sequence order, 𝑍𝛾𝑌𝛽𝑋𝛼. shown in Equation 3a with the corresponding angles calculated based on the rotational matrix entry 27 (Equation 3b). Regardless of the approach, once the rotation matrix of the moving segment relative to the reference segment is identified, clinical rotation angles can be calculated from the three angles elicited from the rotation matrix (F/E, Ab/Ad, and I/E). 𝑅𝐶 𝑖𝑗 = 𝑍 𝛾 𝑌𝛽𝑋𝛼 = [ cos 𝛾 cos 𝛽 cos 𝛾 sin 𝛽 sin 𝛼 + cos 𝛼 sin 𝛾 − sin 𝛽 cos 𝛼 cos 𝛾 + sin 𝛼 sin 𝛾 cos 𝛼 sin 𝛾 sin 𝛽 + sin 𝛼 cos 𝛾 cos 𝛼 cos 𝛾 − sin 𝛼 sin 𝛽 sin 𝛾 − cos 𝛽 sin 𝛼 cos 𝛽 cos 𝛼 − cos 𝛽 sin 𝛾 sin 𝛽 Eq 3a ] Eq 3b 𝛼 = tan−1 ( 𝑅23 𝑅33 ) , 𝛽 = sin−1(𝑅13) , 𝛾 = tan−1 ( −𝑅12 𝑅11 ) 2.2.2 Method 2: Body-fixed floating axis joint coordinate system The next approach, the body-fixed floating axis method, was developed by Grood and Suntay [148]. The Grood and Suntay system has fixed and floating axes and has been utilized by researchers for the ankle, knee, hip, trunk, and back [135,137,149–152,154]. In this approach, it is first necessary to specify the Cartesian coordinate system (labeled x, y and z) in each segment and the fixed body axes of the joint coordinate system (labeled e1 and e3). In general, the two non- orthogonal, anatomically-based axes (or fixed body axes) are selected by the user used to calculate joint angles. One axis is embedded in each segment; and they are labeled e3 and e1, as shown in in Figure 8. The fixed body axes of each segment are selected from the Cartesian coordinate system axes (e.g., e3 is in the direction of the x axis of the proximal segment). Rotations of one body about its own fixed body axis, while holding the other body stationary, corresponds to relative rotations. The fixed axes move with their corresponding bodies so that the relationship between the two bodies (and axes) changes as they move. Because the fixed body axes, e3 and e1, move with the bodies they are embedded within; the direction of the fixed body axes cannot be parallel. The choice of fixed body axes for the thumb is shown in Figure 8, where rotation of the distal segment relative to the proximal segment about the y-axis, or e1, defines F/E movement. The third axis was 28 defined by the axis perpendicular to both fixed body axes and is called e2 or the floating axis, where rotation of the distal segment relative to the proximal segment defines Ab/Ad (Figure 9). Rotation about the x axis, or e3, of the distal segment relative to the proximal segment defined I/E (Figure 10). It was computed using Equation 4 and moves in relation to both bodies. Each fixed body axes should be selected so that they are not parallel, meaning e1 and e3 cannot point in the same direction (e.g., both cannot be in the Z direction of each segment). The fixed body and floating axes create a right – handed coordinate system so that relative rotations between the two bodies could be determined. Capital letters X, Y, Z are used to denote the Cartesian coordinate system axes of the non-moving segment with base vectors I, J, K. Similarly, lower case letters x, y, z are used to denote axes of the moving segment with base vectors i, j, k. Each axis of the coordinate system of each segment is unitized. 𝑒2 = 𝑒3 × 𝑒1 |𝑒3 × 𝑒1| Eq 4 Figure 8. The proximal and distal segments embedded with their respective coordinate systems. One axis is closely aligned with the longitudinal axis of the segment. Flexion- Extension occurs about the Y-axis (calculated by angle α). 29 Proximal Distal Figure 9. The proximal and distal segments embedded with their respective coordinate systems. The green (x/e3) axis points anteriorly, the blue (y/e1) axis points laterally, and the red (z/e2) axis points out of the page. Abduction- Adduction (calculated by angle β) occurs about the z-axis. 30 Proximal Distal embedded with Figure 10. The proximal and distal segments their respective coordinate systems. The green (x/e3) axis points anteriorly. Internal-External (calculated by γ) occurs about the about the x-axis. Table 4 identifies the clinical angles determined by Grood and Suntay [148]. F/E can be determined using cosine or sine (shown in Table 4). The range of values for which each trigonometric function yields a unique relationship is limited. For example, the cosine function is limited at 0° ≤ α ≤ 180° because the cosine function is only unique between values 0° and 180°, meaning cos(α)=cos(360-α), or cos(α)= cos(-α). Thus, using cosine does not allow for any value greater than 180°, which would correspond to hyper-extension, or a “thumbs up” position. 31 Figure 11. An example of flexion > 90° resulting in a reflected curve using the Grood and Suntay approach for looking at flexion and extension of the thumb. It is expected to reach 94 degrees. Instead, flexion reaches 90 degrees and starts to reflect back below. An alternative to the cosine equation is the sine function (shown in Table 4). A challenge when using the sine function is similar to that of cosine. The use of the trigonometric function sine is only unique for values between -90° ≤ α ≤ 90° due to the reflection at 90° (shown in Figure 11), meaning sin(α)=sin (180- α). Thus, any values greater than 90° of hyper-flexion, or α > 90°, result in non-unique output values because there are multiple α values that correspond to the value for sine. To account for these limitations, a method was proposed by Dabirrahmani and Hogg. to allow for the inclusion and continuous curve that for the thumb would include hyper-extension or hyper-flexion values [163]. Typically, the range for thumb flexion is 0° ≤ α ≤ 90°, but in some cases could exceed 90° using Grood and Suntay’s method. The flexion angle is determined by the relative magnitudes of the cross and dot products of the anterior-posterior axis and the floating axis. Equation 5a accounts for hyper-flexion, but not for values less than 0. The numerator of Eq 5a, gives the magnitude of the resulting vector, which is always positive and coincides with the 32 current direction of the medial-lateral axis. However, the sign of a vector is typically determined via the right-hand rule. To account for hyper-extension, Equation 5c determines the sign (n) of the numerator of Eq 5b by taking the dot product of the cross product of anterior-posterior axis and the floating axis with the medial-lateral axis. The multiplication of n in the numerator switches the direction of the medial-lateral axis which essentially negates the sign of the numerator. Table 4. Clinical Rotations defined by Grood and Suntay and Dabirrahmani described for the right knee. For the knee, the i, I axes (fixed body axis, 𝑒1) point medially, the j, J axes point anteriorly and the k, K (fixed body axis, 𝑒3) point anteriorly. The local coordinate system is defined by {𝑒1,𝑒2,𝑒3}={I, 𝑒2, 𝑘} Motion Option 1 Option 2 Flexion (𝛼) cos 𝛼 = 𝐽 ∙ 𝑒2 sin 𝛼 = −𝑒2 ∙ 𝐾 Adduction (β) cos 𝛽 = 𝐼 ∙ 𝑘; ± 𝜋 2 External rotation (𝛾) cos 𝛾 = 𝑗 ∙ 𝑒2 sin 𝛾 = −𝑒2 ∙ 𝑖 tan 𝛼 = |𝐽 × 𝑒2| 𝐽 · 𝑒2 tan 𝛼 = 𝑛 |𝐽 × 𝑒2| 𝐽 · 𝑒2 𝑛 = (𝐽 × 𝑒2) ⋅ 𝐼 | 𝐽 × 𝑒2| Eq 5a Eq 5b Eq 5c If n=1, the cross product is in the same direction of the medial-lateral axis; and if n = -1, the cross product is pointed in the opposite direction of the medial-lateral axis. Ab/Ad are represented with β, which is equal to the inverse cosine of the dot product between two fixed body axes. I/E, which 33 are denoted by γ, are rotations about the longitudinal bone axis or the inverse cosine of the dot product between the anterior-posterior axis of the moving segment and the floating axis, 𝑒2. 2.3 Discussion of Advantages and Disadvantages of Each Approach Both approaches have advantages and disadvantages. While Euler angles are commonly used in many biomechanical based applications, mathematical issues exist that make its application to the thumb difficult [162,163]. One issue, termed gimbal lock, occurs when the second rotation is 0° or 180°, i.e., when the first and third axes are parallel (e.g. Figure 12). When this occurs, it causes the equation output to bounce between ±180°. In the case where the second rotation represents F/E, gimbal lock could occur. For example, during thumb joint extension. Gimbal lock could also occur when the second rotation reaches 90°, an issue originating from the sine function only having unique relationships between -90° and 90°. This function is known to have similar issues for other joints of the body. For example, during Ab/Ad movement of the shoulder or I/E of the elbow where angles often reached or exceeded 90° [161,164,165]. Figure 12. An example of gimbal lock occurring at a second rotation reaching 180° indicated by the black boxes using the Euler approach. 34 A B Figure 13. A set up of two segments with motion capture markers. The moving segment started at approximately 0° (horizontal (A)), flexed to 90° (B) and returned to 0° (A). The plot output of this movement is shown in Figure 14. Figure 14. An example of using the body–fixed floating axis coordinate system with one segment relative to another manually moved to 90° of flexion and back to 0°. The Ab/Ad and I/E rotation movements have minimal angle movement as they were only a result of user error. Additionally, other challenges arise with Euler angles as they are sequence-dependent, meaning that different rotation orders result in different coordinate systems and, subsequently, different angle values. This can be seen in Figure 15 when a different rotation angle sequence is used and the output resulted in different angle values. To create a consistent system to describe joint rotations, the International Society of Biomechanics standardization has recommended the 35 first rotation to occur about the axis embedded on the proximal segment, and the final rotation about the axis embedded on the distal segment [84,166]. Figure 15. An example of a human participant’s thumb values resulting from a different choice of rotation order using different Euler (Cardan) angle sequences. RxRzRy sequence (left) and RzRyRx (right), with the left plot representing the rotation about Y, Z, then X and the right plot showing rotation about X, Y, then Z. For analysis of the thumb, the Grood and Suntay approach has fewer disadvantages and more advantages in the application for the thumb in comparison to the Euler approach. First, this approach is sequence-independent, which eliminates the possibility that selection of an order sequence would lead to inaccurate/inconsistent angle values (e.g. Figure 15). Although this approach does not guarantee orthogonality, as the rotation axes were taken from two separate coordinate systems, this approach has several advantages that outweigh the issue presented here. Furthermore, this approach is similar to the Euler method in that the relative rotations of two – body segment coordinate systems are expressed by three rotation angles. However, one difference using the method by Grood and Suntay is that the rotations are about the coordinate system axes of both the proximal and distal segments, rather than the sequential rotations about axes of an individual coordinate system. This method also allows for easier communication of joint angles to clinicians, who expressed that the angles were more intuitive because the individual axes were 36 embedded in each body segment [166]. Furthermore, rotation motion about the joint coordinate system is commutative, meaning the order of rotation does not need to be specified. 2.4 Conclusion Each method has benefits and disadvantages and both frequently used in human body kinematics. The appropriateness of each approach for each application is at the discretion of the researcher. However, both methods require careful interpretation to ensure that the reported data accurately represented joint movement. In this study, the body-fixed floating axis joint coordinate system method was determined to be more appropriate, had less disadvantages and was applied to determine the joint angles of the thumb. 37 CHAPTER 3: RANGE OF MOTION OF THE THUMB FOR THE HEALTHY AND ARTHRITIC POPULATION 3.1 Introduction Osteoarthritis (OA) has been one of the most debilitating joint diseases worldwide and has affected more than 54 million people [7,167]. Data has indicated OA was most common in the knee, hip, and hand [7,168]. Hand OA has impacted over 48% of men and 51% of women in at least one joint [11,169]. Hand OA has been shown to be most prevalent at the base of the thumb, or the carpometacarpal (CMC) joint [9–11,45,170]. Furthermore, CMC OA had a disproportionally larger frequency in females compared to males, especially over the age of 50 [11,31,52,61,171]; and data showed prevalence for both sexes increased with age [9,13,45,169]. Regardless of sex, thumb OA has caused considerable discomfort and changes to function. OA has been known to cause joint pain and reduced range of motion (ROM) due to anatomical changes such as ligament laxity, joint space narrowing, and erosion of the joint surfaces [29,172– 175]. These anatomical changes have led to altered motions by affecting the alignment and tissues of the other joints of the thumb as they are all part of a kinetic chain [21,103]. As a result of these anatomical changes, the thumb demonstrated a reduced ability to carry out certain tasks. OA caused a lack of ROM as well as significant pain, thus leading to reduced function and quality of life [12,18,24]. Certain tasks that were noticed to produce pain included opening jars, cutting food, or tasks that required the dexterity, strength, and mobility of the thumb [3,11,12,24,61]. Pain during movement led to challenges in carrying out activities of daily living (ADLs), thus leading to a lack of independence. In order to relieve pain and improve ranges of motion of those with thumb CMC OA, several conservative treatments have been employed. Commonly used treatments included non- steroidal anti-inflammatory drugs (NSAIDs), thumb-stretching and strengthening exercises, 38 splinting, and corticosteroid injections [12,28–31,52,70]. However, these treatments often only provided short-term relief and were not effective for those with severe thumb OA. In order to assess if changes occurred as a result of conservative treatments, medical professionals used standard measurement tools. The most common measurement tool used for clinical assessment was a goniometer. While this has been the standard method for measuring joint motion in clinics, goniometers have been reported to have low accuracy and poor intra-rater reliability [38,40–42]. Additionally, goniometers only had the ability to measure joint angles in a single plane. The use of a goniometer lacked the ability to capture the unique, three-dimensional (3D) motion of the thumb. The thumb CMC has been described as a joint with complex movements as it does not move like a typical hinge or ball in socket joint. Thus, the motion of the thumb should be measured with tools that have 3D measurement capability. Some researchers have used 3D methods, such as motion capture, to quantify the complex motions of the thumb joints [49,81,103,117,121,143,176]. However, data reported via 3D methods on healthy individuals often did not include ROM at each specific joint [67,115,130]. Motion data often reported on the thumb included averages of overall thumb motion, which did not provide detail on the individual contributions of each joint [102,113,119,131,177]. Other studies only included data from a small sample [66,103,115]. Additionally, there remains a need to compare data between sexes because of the large disparity between female and male cases. Furthermore, with the increasing number of cases due to aging, it is essential to investigate the difference in thumb function due to age. More specifically, measurable thumb motion changes due to aging could indicate precursors that may lead to thumb CMC OA even prior to pain. If found early, there may be the possibility to delay significant loss of function, thus extending independent living. 39 Comparison of heathy data between sexes and ages could be beneficial to a wide range of individuals. Gathering a better understanding of healthy thumb motion could be used to improve clinical care and identify personalized treatment plans for those with CMC OA to determine if function is being restored. Currently, there is little research reported on the trends seen in thumb motion of healthy individuals compared to those with osteoarthritis [49,54,67,115,117,128]. Therefore, in order to understand the changes in kinematics of those with thumb CMC OA, healthy thumb function needs to be established as a baseline. Thus, the goal of this work was to understand the movement contribution of the IP, MCP, and CMC joints of the thumb, specifically during flexion, extension, and opposition of healthy and individuals with CMC OA at three time points: pre-surgery, 3 months post-surgery, and 6-months post-surgery. 3.2 Methods 3.2.1 Testing All testing and participant data were conducted in accordance with Michigan State University's Institutional Review Board and all individuals consented to participation (IRB#00006111, IRB#00006525, IRB# 2021-148). Participant data collection included the following: Quick Disabilities of Arm, Shoulder and Hand (QuickDASH), visual analogue scale (VAS) pain score, and 3D motion measurements. The QuickDASH asked the level of difficulty to complete daily tasks such as cutting food with a knife. A lower score indicated less difficulty completing tasks. Participants were asked to report their VAS pain score for their right thumb (for healthy participants) or their surgical thumb (for CMC OA participants). The score represented their self-reported pain level in the 48 hours prior to arriving for testing, where a higher score represented more pain. 40 3.2.2 Participants All healthy participants had no diagnosis of hand or thumb CMC OA (i.e., no clinical signs of osteoarthritis), no prior surgery or injury to their thumb, all were right-handed, over the age of 18, and were not pregnant. Two healthy groups of men and women were tested: younger healthy (YH) and older healthy (OH). Younger healthy participants were between the ages of 18 and 39, while older healthy participants were those over the age of 40. The second testing group included CMC OA participants with doctor diagnosed thumb CMC OA (with and without clinical signs) and consented to LRTI surgery. All OA participants had an average Eaton classification of 3 out of 4, which is characterized with partial dislocation of the CMC joint, bony erosion, and joint space narrowing. Healthy participants were tested once, and surgical participants were tested before surgery, 3-months post-surgery, and 6-months after surgery. 3.2.3 Motion Testing A B Figure 16. Six camera motion capture set-up with testing device on the table where participants sit (A). The testing device with a participant’s forearm and hand resting on the plate at the beginning of testing (B). The equipment used for this research included six infrared motion capture cameras (Qualysis, Gothenburg, Sweden) to capture 3D movement at a sample rate of 100 Hz (Figure 16A) and a custom-built testing device that supported their forearm and rested their hand on a metal plate (Figure 16B). Reflective markers pods were placed on the three thumb segments (distal, 41 proximal, and metacarpal phalanges) each with 5 mm diameter markers labeled with markers 1- 12 in Figure 17. Individual single markers on the base of the 2nd and 5th metacarpophalangeal (MCP) joints and the medial and lateral sides of the wrist (Lister’s tubercle=tubercle of the radius), measured 13mm in diameter labeled as markers 13-16 in Figure 17. Table 5. Individual markers and marker pod locations of the thumb Marker Number 1-4 Location Distal Phalange 5-8 9-12 13 14 15 16 Proximal Phalange Metacarpal 2nd MCP 5th MCP Lister’s Tubercle Ulnar Styloid 2 4 13 14 Figure 17. Marker pods on segments of the thumb, single markers on the sides of the wrist, 2nd and 5th finger MCP joints. 42 Table 6. Marker locations used to create vectors for coordinate systems on each segment Segment Distal Proximal Metacarpal Dorsum of Hand Marker 13-Marker 15 Y-Axis Vector X-axis Vector Marker 3-Marker 4 Marker 1-Marker 2 Marker 7-Marker 8 Marker 5-Marker 6 Marker 9-Marker 10 Marker 11-Marker 12 Z-axis Vector X × Y X × Y X × Y Marker 15-Marker 16 Z × X Z Z z Z Figure 18. The proximal and distal segments of the thumb embedded with their respective coordinate systems. One axis is aligned with the longitudinal axis of the segment, while the other two are mutually orthogonal. Local coordinate systems were created on each segment of the thumb and the dorsum of the hand using the vectors in Table 6. The capital letters X, Y, Z are used to denote the Cartesian coordinate system axes of the non-moving segment with base vectors I, J, K (Figure 18). Similarly, the lower case letters x, y, z are used to denote axes of the moving segment with base vectors i,j,k (Figure 18). Each axis of the coordinate system was created using the positional data from each marker. For example, the process of calculating the distal, proximal, and metacarpal coordinate systems included the following steps: the X-axis on each pod was calculated by subtracting the distal marker (e.g., Marker 1) from the proximal marker (i.e., Marker 2), Y-axis by subtracting the lateral marker (i.e., Marker 3) from the medial marker (i.e., Marker 4), and the Z-axis vector was calculated by taking the cross product of the X- and Y-axis vectors. Finally, each vector was unitized. The resulting coordinate system of each segment was the x-axis pointing distally along the bone, the y-axis pointed laterally, and the z-axis pointed superiorly. A similar method was used to create the coordinate system on the dorsum of the palm. The X-axis was calculated by 43 subtracting Marker 13 from Marker 15. The Z-axis was calculated by subtracting Marker 15 from Marker 16. Finally, the cross product of the Z- and X- axis created the Y-axis. After each local coordinate system vectors were created, orthogonality was confirmed by taking the cross product of the other two (e.g., x-axis crossed with the y-axis to create a ‘new’ orthogonal z-axis; The y- axis crossed with the ‘new’ z-axis to form the ‘new’ orthogonal z-axis). The axes of each coordinate system were unitized. 3.2.4 Testing Protocol The motions captured were isolated flexion–extension (F/E) and opposition. Participants were instructed to perform two separate motions: isolated F/E and opposition. Isolated F/E consisted of a maximum flexed and extended posture of each thumb joint three times consecutively to the best of their ability (Figure 19). Each patient was instructed to “bend the joints of their thumb as much as they could followed by extending the joints of their thumb as much as possible by bringing their thumb nail back towards themselves.” During isolated F/E the maximum values of flexion and extension were calculated. 44 A B C Figure 19. Isolated flexion-extension of the thumb starting in a neutral position (A), at maximum flexion (B), and maximum extension (C). 45 A B C D F E to collect Steps Figure 20. starting opposition data. A) towards position, B) adduction dorsum of hand, C) maximum extension (‘thumbs-up’), D) largest arc prior to oppose to the base of the 5th MCP (palmar abduction), E) completed opposition, F) moving thumb base of the 5th MCP (palmar abduction), completed E) the opposition, and F) moving thumb back to the starting position. Opposition was described and performed as starting with the thumb next to the index finger (Figure 20A), moving the thumb backward toward the dorsum of the hand (or an adducted thumb, Figure 20B), moving into a maximum extended thumb position (Figure 20C), circling the thumb around to a maximum palmar abduction position (Figure 20D), reaching the tip of the distal aspect of the thumb to the base of their 5th metacarpal (palm side of the 5th MCP joint, Figure 20E), then sliding the tip of the thumb along the palm, and finally returning to the starting position (Figure 20F). Participants were instructed to perform this motion three times. Both motions were performed by 46 the researcher during the test so that participants would be able to follow along if steps to execute the motion were forgotten. Within opposition, maximum values of flexion, extension, abduction, and adduction of each joint were calculated. The 0° position for the F/E and Ab/Ad was identified as the thumb positioned alongside the index finger as seen in Figure 20A, when each segment of the thumb is parallel with the x-axis. Joint motion was analyzed using the method developed by Grood and Suntay [148]. This method employed two non-orthogonal anatomically based axes (or fixed body axes) embedded in each segment, labeled e1 and e3. Each fixed axis moved with each body so that the relationship between the two bodies changed as they moved (Figure 21). The third axis was the axis perpendicular to both fixed body axes, e2, also called the floating axis determined by Equation 7a and moved in relation to both bodies. A right-handed coordinate system was set up with the fixed body and floating axes where relative rotation between the two bodies determined joint angles. The details of this process are located in Chapter 2. α Figure 21. X-, Y- and Z-axes of the joint coordinate systems on the distal, proximal, and metacarpal phalanges. The X-axis coincides with the fixed body axes e3, while the Y-axis corresponds to the fixed body axis e1. The floating axis, e2, is the cross product between e3 and e1. For the purpose of this chapter, joint angles during flexion, extension, and opposition were found for the IP, MCP, and CMC. The angle α represents F/E, which was the rotation of the 47 moving segment relative to the fixed segment about the Y-axis of the fixed segment (Table 7). For example, movement of the distal phalange relative to the proximal phalange about the Y-axis of the proximal phalange determined the flexion angle of the IP joint (Figure 21). The flexion angle was determined by the relative magnitudes of the cross and dot products of the anterior-posterior axis (Z) and the floating axis (Equation 7b). Maximum and minimum values of flexion and extension were determined by Equations 7b-7d. Equations 7b-7d were published by Dabirrahmani and Hogg, as a modification of the Grood and Suntay method [163]. This modification computed hyper-flexion (or angles ≥ 90°) (Equation 7b) and hyper-extension (or angles ≤ 0°) angles (Equations 7c-7d). In Equation 7b, the sign of the numerator was determined by the resulting magnitude of the cross product, which always produced a positive value. The n variable, defined in Equation 7d, determined the sign of the numerator in Equation 7c. The sign of the vector resulting from the cross product can be determined by taking the negated dot product of 𝑍 × 𝑒2 and Y (Equation 7d). In the case that the vector computed in the numerator, 𝑍 × 𝑒2, is in the opposite direction of the medial/lateral axis (i.e. Y-axis), n=-1, thus switching the direction. If 𝑍 × 𝑒2 is in the same direction of the medial/lateral axis, n=+1. The final, Equation 7c, is valid for all possible flexion-extension range. For the purpose of this paper, the sign convention for flexion and adduction was denoted to be negative and extension and abduction as positive. Positional data from the marker pods on the distal phalange, proximal phalange, and metacarpal was used to provide joint angles for the IP and MCP. The next step was to provide joint angle data for the CMC joint. To calculate angles at the CMC joint, the metacarpal pod and the individual markers on the back of the hand were utilized. First, a local coordinate system (LCS) on the dorsum of the hand was created using the 2nd MCP marker (Figure 22) and the markers on 48 either side of the wrist (radius and ulna markers). The radius marker (located on Lister’s tubercle) and the 2nd MCP marker formed the X-axis, and the ulna and radius markers formed the Z-axis. The Y-axis was calculated by taking the cross product between the Z- and X- axes. Flexion- extension was relative rotation of the moving segment (metacarpal) relative to the fixed segment (dorsum of the hand) about the Y-axis of the fixed segment (into the page) (Figure 22). Flexion and extension were calculated for isolated F-E and opposition motions. Additionally, abduction and adduction (Ab/Ad) were calculated for the opposition motion using Equation 7e, represented by the angle β. Abduction was determined to be the relative rotation of the moving segment (metacarpal) relative to the fixed segment (dorsum of the hand) about the floating axis (which is parallel to the Z-axis, in which each thumb segment has 0° of flexion) (Figure 22). To calculate the Ab/Ad angle, a dot product between the Y-axis of the fixed segment and the X-axis of the moving segment was performed. Next, the inverse cosine of the dot product result was calculated. Additionally, because the cosine function is only unique between values 0° and 180°, 90° was subtracted from the calculated inverse cosine angle produced in the previous step to ensure the values are in the first and fourth quadrants. Data sets from isolated F/E and opposition motions were processed with custom-made MATLAB scripts (Mathworks, Inc.). 49 Radius Marker Figure 22. Local coordinate systems of the dorsum of the hand using the 2nd MCP marker. The radius marker and the 2nd MCP marker made up the X-axis, the wrist markers created the Z- axis. The Y-axis was the cross product between the Z- and X- axes which goes into the page. Table 7. Clinical Rotations defined by Grood & Suntay and Dabirrahmani & Hogg 𝑒2 = 𝑒3 × 𝑒1 |𝑒3 × 𝑒1| tan 𝛼 = |𝑍 × 𝑒2| 𝑍 · 𝑒2 tan 𝛼 = 𝑛 |𝑍 × 𝑒2| 𝑍 · 𝑒2 𝑛 = (𝑍 × 𝑒2) ⋅ 𝑌 | 𝑍 × 𝑒2| cos 𝛽 = 𝑌∙𝑋 |𝑌||𝑋| ; 𝛽 = 90° − cos−1 ( 𝑌∙𝑋 |𝑌||𝑋| ) Eq 7a. 𝐸𝑞 7𝑏. 𝐸𝑞 7𝑐. 𝐸𝑞 7𝑑. Eq 7e. 3.2.5 Statistical Analysis A linear mixed-effects model was used to analyze motion data. Study groups included as fixed effects were: YH, OH, sex, pre-surgery, 3-months post-surgery, and 6-months post-surgery. The linear mixed-effects model was used to determine the fixed effect of study group on VAS pain score, QuickDASH score, and motion. The random effect of each participant was included to account for between participant variances. Statistical analysis was performed using the SAS/STAT 50 software Version 9.4 (SAS Institute Inc., Cary, NC). Denominator degrees-of-freedom were calculated using the Kenward-Roger approximation, and pairwise comparisons were obtained using the Tukey adjustment for all statistical analysis. P-values <0.05 were considered significant. 3.3 Results 3.3.1 Participants A total of 52 healthy participants participated in this study: 13 OH females (average age 58.0 ± 9.3 years), 13 YH females (average age 25.8 ± 5.1 years), 13 OH males (average age 60.2 ± 11.4), and 13 YH males (average age 28.8 ± 5.6). The YH populations included those aged from 18 to 39 years old. The OH populations included those over 40 years of age. Thirteen CMC OA females (average age 62.8 ± 8.2 years) and two CMC OA males (ages 66 and 72 years old) were tested. Ten right hands and five left hands underwent the LRTI surgery. The 15 OA participants were tested prior to surgery (average time before surgery 21.4 ± 31.8 days), 3-months post-surgery (average time after surgery 90.8 ± 8.5 days), and 6-months post-surgery (average time after surgery 182.1 ± 13.9 days) over an 18-month period which amounted to 45 total testing sessions. All OA participants had surgery at the same clinic, were prescribed a standard postoperative rehabilitation routine, and the CMC joint was immobilized in a splint for 4-6 weeks after surgery. 3.3.2 Standard Clinical Data The VAS and QuickDASH information were collected to evaluate individual function and document any pain. These were standard clinical data questionnaires used to assess self-reported pain and function [178–180]. These results are listed in Table 8. Note, that as with the other data, since there were only two males, a statistical analysis was not conducted. Pre-surgery participants had significantly more pain than YH and OH participants (p<0.001 for females, males had the same trend). On average, pain at 6-months post-surgery was significantly less than pre-surgery 51 (females: p<0.001, males had the same trend). Pre-surgery females reported significantly more function compared to 3- and 6-months post-surgery (p<0.001 for both time points, males showed the same trend). However, two female OA participants (one at each time point post-surgery) did not complete the required number of questions to calculate the QuickDASH score, which may have skewed the significance of the data. Pre-surgery participants had significantly less function (higher QuickDASH score) compared to YH and OH participants (p<0.001 for females, males had the same trend). No statistical differences were found between OA participants at 6-months post- surgery compared to the YH or OH participants (p=0.123). No statistical differences were found for VAS pain score or the QuickDASH between YH and OH participants (p=0.998). Table 8. Average VAS and QuickDASH scores for each of the healthy groups. A higher VAS score=more pain and higher QuickDASH score=less function YH Males (n=13) 0.66 (1.7) 1.2 (2.1) OH Females (n=13) 0.18 (0.61) 4.1 (3.7) YH Females (n=13) 2.4 (4.1) 4.6 (6.6) OH Males (n=13) 1.9 (4.7) 3.1 (5.2) VAS QuickDASH Table 9. Average VAS and QuickDASH scores for each of OA participants recorded pre- surgery, 3-months and 6 -months post-surgery. A higher VAS score=more pain and higher QuickDASH score=less function. Only twelve OA females QuickDASH scores were reported at 3-months post-surgery and twelve OA females at 6-months post-surgery as one female at each time point did not complete the full survey. Two OH females QuickDASH scores were also missing due to not completing the full survey VAS Pre 47.5 (23.5) OA Females (n=13) 3 month 13.7 (17.4) 6 month Pre 15.1 (17.9) 52.5 (36.8) OA Males (n=2) 3 month 8.0 (8.0) 6 month 3.4 (3.4) QuickDASH 16.8 (12.2) 30.1 (19.5) 16.5 (11.2) 53.4 (21.6) 14.8 (3.4) 3.4 (1.1) 3.3.3 Results of Isolated Flexion-Extension Data 3.3.3.1 Young Healthy Data Data for all population groups during isolated F/E are listed in Tables 10 and 11. Average IP and MCP flexion angles demonstrated by the YH males were 71.4⁰ and 59.6⁰, respectively. As 52 for YH females, IP and MCP flexion averages were 76.6⁰ and 63.9⁰, respectively. Average IP and MCP extension angles for the YH males were 39.2⁰ and 3.6⁰, respectively. Average IP and MCP extension angles for the YH females were 35.1⁰ and 16.2⁰, respectively. Average CMC flexion, for both YH male and female groups, were less than 0°, meaning that throughout the isolated F/E movement, YH participants had some range of thumb extension (i.e., they did not flex the CMC joint). Average CMC extension values for the YH males and females were 47.6° and 47.3°, respectively. Table 10. Results from isolated flexion-extension for YH and OH groups. The data listed shows the average (standard deviation) in degrees Joint Angle IP flexion IP extension MCP flexion MCP extension CMC flexion CMC extension YH (n=26) -74.0 (12.4) 37.1 (10.8) -61.7 (12.3) 9.9 (16.8) 10.1 (11.5) 47.5 (5.3) OH (n=26) -64.2 (12.4) 38.7 (11.3) -54.7 (12.7) 11.8 (10.8) 6.0 (8.0) 45.6 (6.0) 3.3.3.2 Older Healthy Data Tables 10 and 11 show results for the IP, MCP, and CMC for the OH groups. Average IP and MCP flexion demonstrated by the OH females were 68.1⁰ and 56.0⁰, respectively. Average IP and MCP flexion demonstrated by the OH males were 60.3⁰ and 53.5⁰, respectively. Extension values for the IP and MCP for OH females were 38.6° and 17.0°, respectively. Extension values for the IP and MCP for OH males were 38.8° and 6.7°, respectively. Additionally, YH joint motion was compared to OH joint motion. CMC extension between both male and female OH and YH groups differed by less than 2°. Similar to the YH groups, the CMC joint stayed at some degree of extension throughout the F/E movement, for the OH groups. Thus, the value of flexion was recorded as a positive angle. Furthermore, OH females performed 50% more CMC flexion than the YH females while OH males performed 66% more CMC flexion 53 than YH males. No statistical differences were found between groups YH and OH females and YH and OH males of the IP, MCP, and CMC joints while performing isolated flexion or extension. Table 11. Result findings for isolated flexion-extension of the IP, MCP, and CMC for YH females, YH males, OH females, OH males. The data shows the average (standard deviation) in degrees Joint Angle IP flexion IP extension MCP flexion MCP extension CMC flexion CMC extension YH Females (n=13) -76.6 (15.4) 35.1 (10.2) -63.9 (10.3) 16.2 (16.4) 12.2 (11.1) 47.3 (4.0) YH Males (n=13) -71.4 (7.6) 39.2 (11.0) -59.6 (13.6) 3.6 (14.7) 8.8 (11.9) 47.6 (6.5) OH Females (n=13) -68.1 (11.6) 38.6 (11.0) -56.0 (9.7) 17.0 (12.2) 6.2 (8.5) 45.5 (4.9) OH Males (n=13) -60.3 (12.0) 38.8 (11.6) -53.5 (32.4) 6.7 (9.2) 5.8 (7.6) 45.8 (6.9) 3.3.4 Surgical Participant Data A total of thirteen OA females (average age 62.1 ± 8.9 years) and two OA males (average ages 66 and 72 years old) were tested. Ten right hands and five left hands underwent the LRTI surgery. The 15 OA participants were tested prior to surgery (average time before surgery 21.4 ± 31.8 days), 3-months post-surgery (average time after surgery 90.8 ± 8.5 days) and 6-months post- surgery (average time after surgery 182.1 ± 13.9 days) over an 18-month period which amounted to 45 total testing sessions. All OA participants had surgery at the same clinic, the CMC joint was immobilized in a splint for 4-6 weeks after surgery, and were prescribed a standard postoperative rehabilitation routine. Table 12. Results from isolated flexion-extension at each thumb joint (IP, MCP and CMC) for OA females (n=13) pre-surgery, 3- and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees Joint Angle IP flexion IP extension MCP flexion MCP extension CMC flexion CMC extension 6 months -58.6 (12.1) 23.4 (16.9) -37.0 (12.0) 22.4 (11.2) -2.20 (10.5) 30.0 (8.8) 3 months -51.8 (17.3) 21.6 (14.0) -33.7(11.0) 21.4 (11.4) 0.16 (6.8) 29.9 (8.2) Pre-surgery -53.1 (15.8) 29.5 (19.3) -43.1 (15.9) 27.5 (14.7) -5.50 (9.5) 33.9 (10.1) 54 Table 13. Results from isolated flexion-extension at each thumb joint (IP, MCP, and CMC) for OA males (n=2) pre-surgery, 3-and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees Joint Angle IP flexion IP extension MCP flexion MCP extension CMC flexion CMC extension Pre-surgery -42.1 (0.79) 45.5 (23.3) -47.9 (21.1) 4.4 (11.1) 7.4 (5.1) 40.2 (7.4) 3 months -44.2 (11.7) 25.4 (6.9) -34.1 (9.1) 9.8 (6.3) 5.3 (2.4) 45.5 (5.4) 6 months -51.9 (8.2) 28.2 (11.1) -36.3 (17.0) 13.6 (3.4) -2.2 (5.2) 42.6 (6.2) Tables 12 and 13 show the average data for the OA females and males. Most participants decreased joint angle ROM at 3-months post-surgery compared to pre-surgery, and most increased at 6-months post-surgery compared to 3-months post-surgery. Furthermore, motion at all joints decreased at 6-months post-surgery compared to pre-surgery, except for IP flexion. This decrease ranged from approximately 2° to 9°. However, for OA males, the trend varied based on joint and time after surgery. No statistical differences were identified for OA females across time points for the IP, MCP, and CMC joints during isolated F/E. 3.3.5 Summary of Isolated Flexion The mean and standard deviations of the flexion and extension angles for YH and OH males and females during isolated flexion-extension are shown in Tables 10 and 11. 20 of 26 YH participants had more IP flexion than MCP flexion, where 11 males and 9 females demonstrated this trend. IP and MCP motions were compared between healthy males and females. 16 of the 26 OH participants had 7° to 20° more IP flexion compared to the MCP. However, when comparing OH females to YH females, OH females performed less IP flexion by 8.5° and less MCP flexion by 7.9°. Additionally, YH females performed 17° more IP flexion than OH males (p=0.039). On average, OH males had 11.1° less IP flexion compared to the YH males. For MCP flexion, the OH males performed 6.1° less flexion than the YH males. For the CMC joint, OH females performed 55 more CMC flexion compared to YH females by approximately 6°. OH males demonstrated less CMC flexion by 3° compared to YH. There were no statistical differences found between YH males and females, nor were there statistical differences between OH males and females for any isolated joint flexions (IP, MCP, and CMC). Additional comparisons were made between the healthy females and OA females. YH females performed statistically more isolated MCP flexion than OA females at all time points (p<0.040). Pre-surgery and 6-months post-surgery OA females performed statistically more isolated CMC flexion compared to the OH females (p=0.024). No statistical differences were found between healthy females and OA females pre- or post-surgery when performing isolated IP flexion. 3.3.6 Summary of Isolated Extension While performing extension (during isolated flexion-extension), 46 of 52 healthy participants had more extension in the IP joint than MCP joint. Only one OH female and one OH male had more MCP extension than in the IP. Additionally, four YH and one OH participant demonstrated no extension in the MCP, meaning the MCP had a flexed posture while executing the movement. On average, extension of the IP, MCP, and CMC were within 4° when comparisons were made between just healthy (OH and YH) males and females and between only the OA females at each time point. No statistically significant results were obtained for IP, MCP, and CMC extension for any of the groups (YH, OH and OA). Additionally, comparisons were made between OA females pre- and post-surgery and healthy groups. OA females at all time points performed less IP extension than OH and YH females, but this was not statistically significant. Additionally, MCP extension performed by OA females pre-surgery and post-surgery was significantly larger than OH and YH males (p<0.042). 56 Similarly, CMC extension was found to be significantly less between OA females pre-surgery compared to all healthy groups (p<0.004) as well at 6-months post-surgery compared to all healthy groups (p<0.002). 3.3.7 Results of the Opposition Data 3.3.7.1 Young Healthy Data In this research, joint angles of the IP, MCP, and CMC during opposition for YH males and females are shown in Table 14 and 15. Average IP and MCP flexion angles performed by the YH males were -30.1⁰ and -53.7⁰, respectively. As for YH females, IP and MCP flexion averages were -20.0⁰ and -56.3⁰, respectively. However, in the YH group, one male and two female participants’ IP joints were extended throughout the duration of the opposition movement (i.e., never flexed). The average IP and MCP extension for YH males were 38.1⁰ and 4.1⁰, respectively. However, four of the YH males did not extend their MCP joint throughout the F/E movement. Average IP and MCP extension angles for the YH females were 36.8⁰ and 16.4⁰, respectively. Average CMC extension performed by YH females and males was 48.6° and 49.1° of extension, respectively, and near 0° of CMC flexion during the opposition motion. Abduction and adduction during opposition of each thumb joint were also calculated. YH females performed 8.1° and -7.8° of IP abduction and adduction, respectively. YH males performed 8.7° and -11.7° of IP abduction and adduction, respectively. Additionally, YH females performed 26.3° and -18.5° of abduction and adduction, respectively, at the MCP joint. YH males performed 20.7° of abduction and -22.7° of adduction at the MCP joint. One YH female and three YH males during opposition did not perform adduction of the CMC joint. Additionally, for the CMC joint, YH females and males performed 36.5° and 39.2° for abduction and -11.8° and -5.1° for adduction, respectively. Comparisons were made between the female and male joint data for 57 both F/E and Ab/Ad movements. F/E was not significantly different between YH male and YH females for any of the joints (p=0.937). Additionally, Ab/Ad was not significantly different between YH male and YH females for any joints (p=0.967). Table 14. Summary of YH and OH joint angles for the IP, MCP, and CMC during opposition. Data listed shows the average (standard deviation) in degrees Joint Angle IP flexion IP extension IP Abduction IP Adduction MCP flexion MCP extension MCP Abduction MCP Adduction CMC flexion CMC extension CMC Abduction CMC Adduction YH (n=26) -25.1 (22.3) 37.8 (10.1) 8.40 (7.9) -9.72 (7.6) -55.0 (7.8) 10.3 (15.1) 23.5 (10.1) -20.6 (7.8) 0.8 (11.9) 48.8 (6.1) 37.8 (6.1) -10.0 (8.1) OH (n=26) -31.1 (17.1) 35.3 (10.7) 9.18 (12.9) -11.6 (6.9) -52.1 (11.4) 11.2 (12.2) 18.2 (8.9) -19.6 (13.1) -4.7 (10.7) 46.8 (6.8) 40.0 (6.2) -2.8 (7.9) 3.3.7.2 Older Healthy Data This study also collected joint angles during opposition for OH males and females (Table 14-15). Average IP and MCP flexion angles performed by the OH females were -28.8 and -54.5⁰, respectively. As for OH males, IP and MCP flexion averages were -33.4⁰ and 49.7⁰, respectively. Average IP and MCP extension angles for the OH females were 36.6⁰ and 13.4⁰, respectively. Average IP and MCP extension for OH males were 34.0⁰ and 9.0⁰, respectively. OH females and males performed -5.3° and -3.5° of CMC flexion and 46.7° and 46.8° of CMC extension, respectively. CMC flexion was not achieved by five OH participants (3F and 2M). OH males and females’ abduction and adduction joint angles during opposition were also calculated. For the IP joint, OH females and males performed 11.4° and 7.0° of abduction and - 11.1° and -12.1° of adduction, respectively. Additionally, OH females and males performed 21.5° and 15.0° of abduction and -22.7° and -16.5° of adduction, respectively, for the MCP joint. As for 58 the CMC joint, OH females and males performed 40.3° and 39.6° for abduction and -4.0° and - 1.7° for adduction, respectively. A total of eight OH participants (4F and 4M) were able to adduct at the CMC joint. Additionally, OH females had less CMC abduction compared to the OH males. IP, MCP and CMC Ab/Ad was not significantly different between OH males and females. Table 15. Summary of YH and OH female and male joint angles for the IP, MCP, and CMC as performed during opposition. The data listed shows the average (standard deviation) in degrees YH Males Joint Angle - (n=13) Opposition -30.0 (19.1) IP flexion 38.1 (10.8) IP extension 8.70 (8.1) IP abduction -11.7 (7.6) IP adduction -53.7 (7.4) MCP flexion 4.1 (16) MCP extension 20.7 (13.9) MCP abduction -22.7 (6.4) MCP adduction 0.9 CMC flexion 49.1 (7.0) CMC extension 39.2 (6.3) CMC abduction -8.2 (9.3) CMC adduction YH Females (n=13) -20.0 (24.1) 37.5 (9.4) 8.10 (7.7) -7.80 (7.0) -56.3 (8.2) 16.4 (13.4) 26.3 (11.1) -18.5 (9.0) 0.7 48.6 (5.2) 36.5 (5.5) -11.8 (6.3) OH Females (n=13) -28.8 (21.6) 36.6 (10.6) 11.4 (16.1) -11.1 (6.0) -54.5 (11.5) 13.4 (14.7) 21.5 (5.0) -22.7 (9.9) -5.5 (10.8) 46.9 (5.6) 40.3 (6.4) -4.0 (9.4) OH Males (n=13) -33.4 (10.2) 34.0 (10.7) 7.01 (8.1) -12.1 (7.7) -49.7 (10.8) 9.0 (8.5) 15.0 (10.6) -16.5 (15.0) -3.9 (10.5) 46.8 (7.8) 39.6 (6.3) -1.6 (5.9) 3.3.7.3 Surgical Participant Data Average joint angles of the IP, MCP, and CMC for OA females and males during opposition are shown in Tables 16 and 17, respectively. OA females significantly increased IP flexion at 6-months post-surgery compared to pre-surgery by 16° (p=0.028). Additionally, on average, OA females demonstrated decreased MCP and CMC flexion 6-months post-surgery compared to pre-surgery, but the difference was not statistically significant (p=0.998). CMC flexion during opposition was not reached by two OA females at 3-months post-surgery and three at 6-months post-surgery. OA females, on average, decreased MCP and CMC extension at 6-month post-surgery compared to pre-surgery, but the change was not statistically significant. On average, IP extension performed by OA females stayed the same 6-months post-surgery compared to pre-surgery. 59 Additionally, on average, OA females decreased IP, MCP. and CMC abduction at 6-months post- surgery compared to pre-surgery, but it was not statistically significant. OA females significantly decreased IP adduction 6-months post-surgery compared to pre-surgery (p<0.001). At the pre- surgery and 6-months post-surgery time points, 6 OA females demonstrated no adduction. Across all three time points, two OA females and one male performed CMC adduction. Table 16. Summary of surgical females (n=13) of the IP, MCP and CMC joint angles as performed during opposition at pre-surgery, 3-months post-surgery and 6-months post-surgery. The data listed shows the average (standard deviation) in degrees Joint Angle - Opposition IP flexion IP extension IP abduction IP adduction MCP flexion MCP extension MCP abduction MCP adduction CMC flexion CMC extension CMC abduction CMC adduction Pre-surgery (°) 3 months 6 months -26.0 (19.2) 27.9 (21.1) 14.2 (13.5) -1.9 (7.7) -43.6 (16.1) 24.7 (13.4) 16.8 (8.0) -18.4 (7.9) -15.6 (8.7) 36.7 (11.2) 40.9 (6.0) -0.3 (4.7) -35.5 (18.9) 27.0 (16.6) 10.8 (7.6) -8.8 (7.1) -34.1 (11.3) 21.9 (10.6) 17.3 (8.4) -14.9 (9.5) -9.1 (9.5) 28.8 (8.8) 32.6 (11.7) 5.9 (13.4) -40.4 (12.7) 28.2 (14.9) 10.8 (11.0) -7.4 (7.3) -33.0 (15.6) 20.4 (10.4) 16.1 (9.8) -14.6 (10.1) -11.8 (10.0) 30.6 (10.4) 34.5 (8.9) -1.4 (6.6) 3 months 6 months Pre-surgery (°) Table 17. Summary of surgical males (n=2) CMC joint angles as performed during opposition at pre-surgery, 3-months post-surgery and 6-months post-surgery. The data listed is shows the average (standard deviation) in degrees Joint Angle - Opposition IP flexion IP extension IP abduction IP adduction MCP flexion MCP extension MCP abduction MCP adduction CMC flexion CMC extension CMC abduction CMC adduction -41.3 (14.0) 30.5 (8.8) 13.2 (8.9) -1.0 (1.7) -29.3 (8.9) 11.8 (5.3) 16.8 (0.9) -6.8 (7.1) -4.8 (3.3) 42.1 (5.3) 35.9 (12.8) -4.2 (10.0) -35.9 (17.1) 25.1 (6.1) 10.0 (5.2) -6.6 (1.1) -33.1 (7.3) 14.3 (4.0) 17.7 (1.9) -9.0 (0.5) -1.5 (1.5) 44.3 (5.6) 34.9 (10.1) 2.5 (0.5) -22.3 (24.6) 31.7 (8.6) 9.9 (0.6) -3.0 (0.5) -37.4 (8.9) 6.0 (9.5) 23.4 (6.6) -7.8 (5.8) -2.1 (5.8) 42.8 (6.4) 30.4 (0.8) -2.3 (1.6) 60 3.3.7.4 Summary of Opposition Data-Flexion The mean and standard deviation of flexion and extension for YH and OH males and females during opposition are shown in Table 16 and 17. Throughout the opposition motion, OH participants demonstrated larger average CMC flexion compared to YH participants by 6°. While OH females showed larger average IP flexion by 8.8° compared to YH females, on average, OH participants performed less MCP flexion compared to the YH. OH females performed 1.8° less MCP flexion when compared to the YH group. OH females performed 4.4° less CMC flexion, compared to YH females. None of the joint flexion angles (IP, MCP, CMC) between each of the healthy groups (OH vs YH) were found to be significant. Flexion during opposition was also compared between OA and healthy groups. MCP flexion angles (during opposition) were found to be statistically larger for YH and OH females compared to OA females at 6-months post-surgery (p<0.004). Lastly, OA females at each time point pre-and post-surgery performed more CMC flexion compared to YH and OH females, but it was not statistically significant. IP flexion was also not statistically different between OA females at any time point compared to YH and OH males and females. On average, trends showed a decrease in MCP flexion, and an increase in IP and CMC flexion between YH, OH, and OA groups (i.e. with increasing age). 3.3.7.5 Summary of Opposition Data-Extension During opposition, on average OH participants had smaller MCP and IP extension angles compared to the YH, with the exception of MCP extension for OH males. OH males and females had less IP extension than YH by 1.0° and 4.1°, respectively. OH females showed less MCP extension than the YH by 3.0°. However, the OH males showed 5.0° more MCP extension than YH males. OH females performed 2° less of CMC extension compared to YH. No statistical 61 differences were found between healthy (YH and OH) males and females. No statistical differences were found across all-time points for IP, MCP, and CMC extension for OA females. However, different trends were found for OA females compared to healthy participants. OA females pre-surgery (p=0.005) and 6-months post-surgery (p=0.047) performed significantly more MCP extension compared to YH males. Additionally, pre-surgery females performed less CMC extension compared to YH males and females (p<0.020). At 6-months post-surgery, OA females performed significantly less CMC extension compared to all heathy groups (p<0.001). 3.3.7.6 Summary of Opposition Data-Abduction On average, abduction of the IP, MCP, and CMC were within 6° when comparisons were made between healthy (OH and YH) males and females, and OA groups pre- and post-surgery. No statistically significant results were obtained for IP, MCP, and CMC abduction for any of the groups (YH, OH and OA). 3.3.7.7 Summary of Opposition Data-Adduction Adduction joint angles were also compared between healthy and arthritic groups, pre- and post-surgery. On average, adduction of the IP, MCP and CMC were within 7° when comparisons were made between healthy (OH and YH) males and females. No statistically significant results were obtained for IP, MCP, and CMC adduction between all healthy groups. On average for OA females, adduction of the MCP and CMC were within 7° pre- surgery compared to post-surgery, and the difference was not statistically significant. OA females showed statistically more IP adduction at 6-months post-surgery compared to pre-surgery (p<0.001). CMC adduction increased 6-months post-surgery compared to pre-surgery, but it was not statistically significant. 62 Comparing OA to the healthy groups, data showed that pre-surgery OA females performed significantly less IP adduction compared to YH and OH males and females (p<0.001). No statistical differences were found for MCP and CMC adduction performed by OA females compared to YH and OH groups. So, overall IP and CMC motions improved for adduction, but only the IP improvement was significant. 3.4 Discussion To understand the progression of OA, changes that occur as individuals age as well as the changes that occur with OA pre- and post-surgery are needed. In this study, data were collected for YH and OH participants at all three thumb joints and compared to the OA participants at three time points. These data are one of the most comprehensive sets of motion data and are uniquely situated in the thumb research space as they used the same in-depth protocol with motion capture on multiple joints in the thumb. Because this work included young healthy individuals, older healthy individuals, and those who were diagnosed with thumb CMC OA, these data provide insight into movement changes that occur as one ages and as disease is identified. Looking across the three groups and age, results showed a consistent trend of less MCP flexion, an increase in IP and CMC flexion as participants aged (i.e., YH to OH to OA females). The increase in CMC flexion is likely due to joint laxity, but the changes associated with a reduction in the middle joint (MCP flexion). The increases in IP flexion suggest that one cannot look only at the MCP joint but must include the entire set of thumb joints. One hypothesis is that the middle joint reduction in motion drives the increases in CMC and IP motions. Additionally, less MCP abduction during opposition was performed by OH groups compared to the YH groups. The inability to abduct the thumb has been reported to be a common 63 sign of those with CMC OA; thus, the OH participants that exhibited these changes in joint motion may have demonstrated an early sign of OA development. Changes in MCP extension, CMC flexion, and MCP abduction have also been linked to the development of the “z-deformity” associated with severe OA [17,19,181]. Additionally, during opposition, OH males and females both demonstrated larger IP flexion and less MCP flexion compared the YH male and female groups. This difference may be a result of compensatory motion. It is possible that the OH group used a different ratio of motion to complete the task (e.g., in opposition) to reach the base of the 5th metacarpal. Similarly, pre-surgery and 6-months post-surgery OA females both performed less CMC extension compared to the healthy (YH and OH) males and females. These changes may be due to motions that occur when performing daily tasks at the CMC joint. Daily tasks often are repetitive and might cause further ligament loosening around the CMC joint and the distal joints of the thumb, particularly as age increases [182]. Therefore, similar to the results of flexion, OH participants exhibited changes in motion at each thumb joint. This could be related to increased joint laxity compared to the YH participants or decreased mobility at the MCP. These findings are unique as most studies have not evaluated each joint’s contribution when performing a specific movement or task. Having this information is critical to understanding progression of the CMC OA. Our data also suggested that the older participants demonstrated increased extension and decreased abduction at the MCP joint. This finding may be an additional indicator that changes at the MCP joint occur prior to thumb OA diagnosis or signs of pain. While the CMC is the most commonly affected joint of thumb OA and the focus of many studies, instability at the CMC causes changes to the ligaments and joints of the whole thumb as they are all linked in a kinematic chain [19,103]. Functional changes at the CMC may not always be the 64 first indicator of thumb OA, therefore the other joints of the thumb are also important for consideration. Furthermore, after removal of the trapezium during the LRTI surgery (which is replaced with soft ligamentous tissue) our data suggests that functional motion of the CMC joint has changed how the thumb performs during different motions post-surgery. Additional changes in motion at each thumb joint post-surgery were seen as the OA participants performed the opposition motion with different joint contributions compared to the healthy participants. 3.5 Limitations In this study, issues could arise from skin movement relative to the bone. However, a rigorous protocol was utilized and markers were placed on easily identifiable bony prominences with little soft tissue below them, which may have helped minimize skin movement. Furthermore, two individuals were trained for marker placement and a pre-study was conducted to ensure that markers were consistently placed across repeat days as well as across the two test assistants. Another limitation was that OA participants had to opt in to testing. Since 70% of individuals receiving surgery volunteered in this study were female, it made the recruitment pool of males smaller and more difficult to recruit. 3.6 Conclusions and Impact This research explored the ranges of motion for younger and older healthy males and females performing two thumb motions. Complex thumb motions of healthy and arthritic individuals were collected and analyzed, which is a more detailed analysis compared to the clinical standard goniometer. These data also provided a comprehensive data set of YH and OH individuals’ thumb motion as well as those with CMC OA at three time points. Furthermore, many studies do not consider the impact of CMC OA at other joints, such as the IP and MCP. Their focus is often centered on the motion of the CMC joint itself where hand OA is most 65 prevalent. Analyzing motion data of all joints of the thumb in the healthy population can lead to earlier detection of changes in motion and function as people age. These data can be used as preventative measures to diagnose CMC OA before an individual may start to experience pain. Further comparisons were made between healthy and OA participants, which is lacking in published literature. Therefore, a more detailed analysis of thumb motion may provide clinicians the evidence to encourage individuals to seek conservative treatment earlier as a means to prevent further progression or development of thumb CMC OA. 66 CHAPTER 4: ISOLATED TTHUMB FORCE DATA FOR HEALTHY AND ARTHRITIC PERSONS PRE- AND POST-SURGERY 4.1 Introduction Nearly 76% of the general population has been impacted by hand osteoarthritis (OA) [183]. Hand OA is a debilitating and prevalent disorder caused by the degeneration of joint surfaces and cartilage [62,69]. The carpometacarpal (CMC) joint, located at the base of the thumb, has been described as a common location of hand OA [45]. Specific causes of CMC OA have not yet been confirmed; however, multiple studies have reported ligament laxity to be a likely factor [184–186]. Ligament laxity has led to joint misalignment and altered loading distribution paths along the thumb. Risk factors for developing hand OA were reported to be age and sex [169,187]. Joint loading was also known to be one risk factor of thumb CMC OA [20,187–189]. The prevalence of CMC OA reported 1 out of 12 men and 1 out of 4 women were affected [13,69,190]. Irrespective of age or sex, individuals with CMC OA may experience joint pain, stiffness and reduced range of motion. CMC OA has also been reported to cause decreased strength and reduced movement of the hand and thumb [2]. These reductions in function led to the inability to grasp, manipulate, and hold items such as cooking utensils or clothing while dressing oneself [8,15,69]. Overall, the reduction of function from CMC OA also resulted in reduced productivity and lack of independence [47]. In severe cases of CMC OA, surgical treatment was conducted to relieve pain and restore function. Additionally, the CMC joint has also be documented as one of the most common sites for surgery in the upper extremity [191]. Although there are many surgical options, the most common surgical procedure for those with thumb CMC OA was ligament reconstruction with tendon interposition (LRTI) [192–194]. 67 The standard clinical tools currently used to measure strength produced by the thumb are the dynamometer and pinch gauge. These tools compared improvement in strength with both healthy individuals and arthritic patients before and after surgery. However, these devices utilized the entire hand and/or the index finger in combination with the thumb to obtain data. Force generation by multiple digits does not provide measured isolated thumb force. Therefore, these clinical devices are not representative of the forces specifically produced by the thumb. To accurately measure isolated thumb force, different devices are necessary. Grip strength in grasping postures has been known to be affected by both wrist position and angle [195–201]. Studies have reported that wrist position changed muscle length while gripping, specifically the flexor digitorum profundus and superficiallis, which changed overall grip strength. One study investigated forearm and wrist rotation on grip strength and reported maximum grip strength decreased significantly when the wrist and palm faced downward, but reported no change in grip strength when the palm faced upward compared to the neutral wrist position [200]. However, a different study reported grip strength was maximal when the wrist was rotated with the palm facing upward [197]. Another study found no difference in grip strength when the palm faced up or down [202]. Additionally, other studies reported grip strength changed as the wrist was flexed or extended [195,196,199,203,204]. Age also affected grip strength, with older adults exerting less force than younger adults. [205]. However, it should again be noted that grip strength does not measure forces produced by only the thumb. There were a limited number of research studies that obtained isolated thumb forces. One comparable isolated thumb force study measured thumb force where the palm faced downward and medially. The palm down position produced more thumb force than in the medial position [206]. Another study by Vocelle et al., tested the effect of an exercise regimen on thumb force in 68 four directions (with the palm oriented medially). Healthy (younger and older) and arthritic individuals were tested at three time points [207]. It is important to note that the studies mentioned above were limited to a population group of only young healthy males, which are not representative of the population diagnosed with CMC OA [201,206]. Based on the limitations associated with standard clinical methods for thumb force quantification, a more detailed analysis of thumb force is needed, particularly before and after CMC OA surgery. Key differences between the healthy population and those with CMC OA are important to effectively determine early onset, disease progression, and range of motion and force generated that has changed pre- and post-surgery. Furthermore, comparisons between the healthy and arthritic population, as well as pre-and post-surgery, using techniques to correctly measure isolated thumb force are lacking. To gain a comprehensive view of how CMC OA has affected thumb function, it is important to make comparisons between healthy and OA groups of isolated thumb forces. Using these data sets, changes pre- and post-surgery can be detected to make an informed surgical tactic and rehabilitation routine. Therefore, the goals of this work were to 1) determine and compare thumb force generation in younger and older healthy males and females without CMC OA to those who have CMC OA pre- and post-surgery, 2) compare thumb force generation at three time points (pre-surgery, 3- months post and 6-months post-surgery) of those that have CMC OA, 3) determine the effect of wrist position on thumb force, 4) determine the difference between thumb force in different directions (push, pull), and 5) establish the effect of different locations (close, far, and comfortable) on thumb force. 69 4.2 Methods 4.2.1 Participant Testing All testing and participant data were collected in accordance with Michigan State University's Institutional Review Board and all individuals were consented (IRB#00006111, IRB#00006525, IRB# 2021-148). Healthy participants were identified as those who did not have hand or thumb OA, no prior surgery or injury to their thumb, were right-handed, over the age of 18, and were not pregnant. Two healthy groups of men and women were tested: younger healthy (YH) and older healthy (OH). Younger healthy participants were between the ages of 18 and 39, while older healthy participants were those over the age of 40. An additional testing group included CMC OA participants with doctor diagnosed thumb CMC OA and had consented to LRTI surgery. Healthy participants were tested once, and surgical participants were tested before surgery, at 3- months, and 6-months after surgery. 4.2.2 Force Equipment and Testing Setup In this study, a custom testing device was created to isolate force generated by the thumb in various postures. The custom testing device included a block mounted on a six-axis load cell (AMTI, Boston, MA), and data were collected at 200Hz. The block had an array of holes spaced approximately 12.7 millimeters apart in 5 rows and 11 columns (Figure 25E) so that the location of applied force could be changed. All data reported were the maximum magnitude of the resultant force vector (Equation 8). |𝑅⃗⃗ | = √ 𝐹𝑥 2 + 𝐹𝑦 2 2 + 𝐹𝑧 Eq 8 70 4.2.3 Equipment for Clinical Force Measures Clinical measurement testing included grip strength, tip pinch, and key pinch. Grip strength was collected using the Jamar Hydraulic Hand Dynamometer, (Model 081028935, Cedarburg, WI) shown in Figure 23. Tip (Figure 24A) and key pinch (Figure 24B) were collected using the Baseline hydraulic pinch gauge (Model 12-0235, White Plains, NY). All data reported for the grip and pinch strength are the average of three trials. Figure 23. The Jamar dynamometer was used to measure hand grip strength. Participants were instructed to use the whole hand to grasp the whole device and squeeze for 2-3 seconds. The average maximum grip strength was recorded. 71 A B Figure 24. A) Baseline hydraulic pinch gauge used to measure tip pinch performed with the index finger superiorly and the thumb inferiorly to execute a “pinch” motion squeezing the button as strength was recorded. B) Baseline hydraulic pinch gauge used to measure key pinch performed with the thumb placed superiorly and with the radial middle aspect of index finger underneath the button to squeeze as strength was recorded. The average maximum pinch strength was recorded. To collect grip strength and pinch measurements, participants sat with the same posture and in the same chair where isolated thumb force was collected. Each participant was asked to grip the dynamometer (Figure 23) with their whole hand, and squeeze as hard as they could for 2-3 seconds. Additionally, to collect tip and key pinch strength, participants were instructed on proper placement of the index finger and thumb. For tip pinch (Figure 24A), the index finger was placed superiorly on the button and the thumb placed inferiorly. For key pinch (Figure 24B, the thumb was placed superiorly on the button, while the inferior aspect of the pinch gauge rested on the lateral aspect of the middle phalanx of the index finger. All grip and pinch strength measurements were performed 3 times and the average across all trials was reported. Additionally, all participants were measured with the elbow extended and slightly abducted. Participants were instructed to apply the maximum force possible without causing pain. 72 4.2.4 Trials and Protocol Participants sat in a chair with their feet flat on the floor, their back against the seat, elbow extended resting on the testing device, and hand resting on a support system (Figure 25). Data collection included isolated thumb forces in two wrist positions: 0° wrist position (Figure 25A, A (a) B E (e) C (c) D (d) Figure 25. A) 0° wrist position thumb push towards the ground, B) 0° wrist position thumb pull in towards the palm, C) 90° wrist position thumb push towards the ground D) 90° wrist position thumb pull in towards the palm E) block system was mounted on the load cell with equally spaced holes where participants placed the peg. (a) 25B)), which had the palm parallel to the ground; and the 90° wrist position, where the palm was positioned vertically (Figure 25C, 25D). In each wrist posture, two force directions were included: a push, which was described as the thumb pushing the peg “downward” (Figure 25A, 25C), and a pull, which was described as the thumb pulling the peg in toward the hand (Figure. 25B, 25D). Participants were instructed to execute each push and pull on the peg with their thumb positioned at a “close”, “far” and “comfortable” location. The close location was described as the peg in the closest hole to the palm in which the pad of the thumb could grip the peg. The far location was described as the location of the peg in the farthest hole laterally away from the hand in which the thumb could grip the peg. The comfortable location was the most comfortable peg location for the individual to grip the peg. For each location (close, far, or comfortable) the participant was 73 instructed to select the peg location that permitted exertion of maximum force during each push and pull. All force locations and directions were performed twice for two to three seconds, and the maximum resultant force across both trials was recorded. 4.3 Statistical Analysis A mixed-effects model was used to analyze the force data. Fixed effects terms included study group, which included males and females in each (YH, OH, pre-surgery, 3-months post- surgery, and 6-months post-surgery), force direction (push and pull), force location (close, far, and comfortable), and wrist position (0° and 90°). All possible two- and three-way interaction terms were also included. A separate analysis was conducted to compare grip strength, key pinch, and tip pinch with isolated force data. The random effect of participants was included to accommodate the repeated measure design. Statistical analysis was performed using the SAS/STAT software Version 9.4 (SAS Institute Inc., Cary, NC). Denominator degrees-of-freedom were calculated using the Kenward- Roger approximation, and pairwise comparisons were obtained using the Tukey adjustment for all statistical analysis. P-values less than 0.05 were considered significant. 4.4 Results 4.4.1 Participants A total of 52 healthy participants participated in this study: 13 OH females (average age 58.0 ± 9.3 years), 13 YH female participant (average age 25.8 ± 5.1 years), 13 OH males (average age 60.2 ± 11.4), and 13 YH males (average age 28.8 ± 5.6), Thirteen CMC OA females (average age 62.8 ± 8.2 years) and two CMC OA males (ages 66 and 72 years old) were tested. Of these individuals, ten right hands and 5 left hands underwent the LRTI surgery. The 15 OA participants were tested prior to surgery (average time before surgery 74 21.4 ± 31.8 days), 3-months post-surgery (average time after surgery 90.8 ± 8.5 days), and 6- months post-surgery (average time after surgery 182.1 ± 13.9 days). Testing occurred over an 18- month period, which amounted to 45 total testing sessions. All OA participants had surgery at the same clinic and were prescribed a standard postoperative rehabilitation routine. The CMC joint was immobilized in a splint for 4-6 weeks after surgery. One three-way interaction term found to be significant was study group/wrist position/force direction (p<0.0214). Force data were reanalyzed with a reduced model that had all the possible two-way interaction terms from the significant three-way term. Thus, two-way interaction terms found to be statistically significant were study group/force direction (p<0.001), wrist position/force direction (p<0.001), and study group/wrist position (p<0.004). Thus, only the fixed effects terms direction, location, group and wrist posture (all p<0.021), and significant interaction terms were kept. A separate analysis was made to include grip strength, key pinch, and tip pinch with isolated force data. 75 4.4.2 Healthy Participant Data 4.4.2.1 Younger Healthy Younger Healthy 0° Force Data ] N [ e c r o F t n a t l u s e R 90 80 70 60 50 40 30 20 10 0 push pull push pull push pull push pull push pull push pull close far comfortable close far comfortable Male Female Figure 26. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for younger healthy males (n=13) and females (n=13) in 0° wrist position. 4.4.2.1.1 0° Force Data The average isolated thumb forces in the 0° wrist position for YH males and females are shown in Figure 26 and Table 18. For both males and females, thumb force generated in the pull direction was larger than the push direction (p<.0001). Additionally, YH males performed significantly more thumb force than YH females in the pull direction (p<0.017) but not in the push direction. YH males performed more thumb force in location (close, far, and comfortable), but none were found to be significant. Averaged across all locations, the difference between the push and pull forces was 20 N for females and 29 N for males. 76 Table 18. Average maximum thumb force data (standard deviation) for young healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position 0° Far Comfortable Far Comfortable Close Pull Push Close (N) 23.5 (8.6) 33.5 (8.0) YH F (n=13) YH M (n=13) 26.2 (10.3) 29.7 (9.4) 26.2 (10.5) 35.7 (14.3) 42.6 (17.0) 57.7 (17.0) 43.8 (16.6) 63.7 (19.8) 49.8 (17.6) 65.4 (22.4) 4.4.2.1.2 90° Force Data Younger Healthy 90° Force Data ] N [ e c r o F t n a t l u s e R 90 80 70 60 50 40 30 20 10 0 push pull push pull push pull push pull push pull push pull close far comfortable close far comfortable Male Female Figure 27. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for younger healthy males (n=13) and females (n=13) in the 90° wrist position. Table 19. Average maximum thumb force data (standard deviation) for young healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position 90° Far Comfortable Pull Close Comfortable Push Far YH F n=13) YH M (n=13) Close (N) 29.9 (10.2) 45.9 (10.8) 26.0 (9.6) 35.3 (7.3) 33.6 (16.9) 42.1 (9.6) 40.9 (13.7) 54.1 (11.1) 35.3 (13.4) 49.5 (12.4) 40.2 (15.9) 55.0 (11.5) 77 The average isolated thumb forces in the 90° wrist position for YH males and females are shown in Figure 27 and Table 19. For the YH group, the 90° wrist position showed similar trends to that of the 0° wrist position. For both males and females, pull force was larger than push force (p<.002). Males also produced more force than females at each location (i.e., close, far, and comfortable), but the difference was not found to be statistically significant. The difference between the push and pull forces, averaged across all locations, was less than 9 N for females and Older Healthy 0° Force Data less than 12 N for males. 4.4.2.2 Older Healthy 4.4.2.2.1 0° Force Data ] N [ e c o r F t n a t l u s e R 90 80 70 60 50 40 30 20 10 0 push pull push pull push pull push pull push pull push pull close far comfortable close far comfortable Male Female Figure 28. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for older healthy males (n=13) and females (n=13) in 0° wrist position. The average isolated thumb forces in the 0° wrist position for OH males and females are shown in Figure 28 and Table 20. Similar to the force data trend of the YH groups, when averaged across locations, OH males generated larger force than OH females in the pull and push directions, but it was not found to be statistically significant. Averaged across all peg locations (i.e., close, 78 far, and comfortable), the difference between push and pull was a maximum of 11 N for females and 26 N for males. In the 0° wrist posture and averaging across all peg locations and participants in each group, the YH females generated less force than the OH females by a maximum of 6 N and 4 N in both the push and pull directions, respectively. For the males, in the 0° wrist posture averaged across all peg locations, the YH males generated less force than the OH males by a maximum of 7 N and 2 N in the push and pull directions, respectively. Table 20. Average maximum thumb force data (standard deviation) for older healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position 0° Comfortable Pull Close Comfortable Far Far Push Close (N) 32.8 (10.8) 38.2 (16.4) OH F (n=13) OH M (n=13) 31.8 (8.3) 36.7 (8.6) 34.8 (11.1) 43.8 (16.2) 48.9 (8.0) 58.6 (17.9) 47.1 (11.9) 65.0 (18.6) 50.8(12.8) 68.8 (22.4) 79 4.4.2.2.2 90° Force Data Older Healthy 90° Force Data ] N [ e c r o F t n a t l u s e R 90 80 70 60 50 40 30 20 10 0 push pull push pull push pull push pull push pull push pull close far comfortable close far comfortable Male Female Figure 29. Average maximum force trials for all directions (push and pull) and locations (close, far and comfortable) for older healthy males (n=13) and females (n=13) in the 90° wrist position. Table 21. Average maximum thumb force data (standard deviation) for older healthy females and males in each direction (push and pull) and location (close, far, and comfortable) in the 90° wrist position 90° Comfortable Pull Comfortable Close Far Far Push Close (N) 34.4 (9.0) 45.0 (14.5) OH F (n=13) OH M (n=13) 27.9 (6.6) 38.6 (12.6) 34.3 (10.1) 48.2 (16.6) 42.4 (11.9) 55.9 (13.0) 37.8 (9.6) 53.4 (12.1) 40.7 (12.7) 60.2 (18.7) Similar to the 0° position on average, 90° pull force was larger than push force. Average OH male thumb force was significantly larger than OH females in the pull direction (p=0.013), but not in the push (p=0.349) direction. Based on the thumb force averaged across all locations, the difference between push and pull was 8 N for OH females and 11 N for OH males. Averaging across all peg locations, the YH females generated less force than the OH females by a maximum of 2 N in both the push and pull directions; but it was not found to be significant. Additionally, 80 YH males generated less force than the OH males in the 90° wrist posture by a maximum of 3 N and 4N in the push and pull directions, respectively. In summary, differences between wrist position, peg location, and healthy (younger and older) males and females produced mixed results. Overall, OH females and OH males generated more force compared to the YH females and YH males, respectively; but this difference was not statistically significant. On average, healthy males generated statistically larger thumb force (combining wrist position and peg location) than healthy females in both younger (p=0.032) and older healthy groups (p=0.013). For all healthy groups, the effect of direction (push vs. pull) on force (combining wrist position, group and peg location) was found to be significant. All OH (males and females combined) generated statistically larger forces than the all YH (males and females combined) when pull force was compared to the push force (p<0.007). However, when separating the older healthy males from females, the same significance was not found. OH females exerted more force than YH females in the pull direction and push directions, but comparisons were not statistically significant. Additionally, OH males exerted more force than the YH males in the pull and push directions; but, again, comparisons were not statistically significant. However, when considering the effect of wrist position within each group (including direction and peg location), only OH females performed statistically larger forces in the 0° compared to the 90° wrist positions (p=0.048). The main effect of peg location when including wrist position, force direction, and group was found to be significant. The effect of peg location on force was found to be significant in only the comfortable location compared to the far location (p=0.021). More specifically, within each group (combining wrist position and force direction) a statistical difference was only found for the OH males in the comfortable location compared to the far location (p=0.012). 81 The effect of wrist position (when force direction, group, and peg location were combined) generated forces that were statistically larger in the 0° wrist position compared to the 90° wrist position (p<0.001). Force generated in 0° thumb pull was statistically larger than the 90° thumb pull (p<0.001), but 0° thumb push was not statistically different compared to 90° thumb push (when group and peg location were combined). 4.4.3 Surgery Participant Data 4.4.4 0° Force Data Figure 30. Average maximum force trials for CMC OA females (n=13) in the close, far and comfortable positions in the 0° wrist position. For the 0° wrist position, the average maximum push and pull forces pre- and post-surgery in the close, far, and comfortable locations are shown in Figure 30 for females. Table 23 shows the data for all female (n=13) surgery patients and Table 23 shows data for male (n=2) surgery patients. 82 Table 22. Average maximum thumb force data (standard deviation) for CMC OA females in each direction (push and pull) and location (close, far, and comfortable) in the 0° wrist position Push 0° Close 0° Far 0° Comfortable Pre (N) 17.5 (8.1) 15.0 (6.5) 17.4 (8.7) 3 month 6 month Pull 15.9 (7.4) 15.0 (7.6) 16.7 (8.1) 20.7 (8.9) 19.6 (8.6) 21.4 (9.2) Pre 22.2 (8.5) 20.9 (12.2) 24.2 (11.0) 3 month 23.4 (9.7) 21.6 (7.6) 23.4 (9.0) 6 month 26.3 (12.0) 29.3 (10.1) 29.7 (11.6) On average, female participants generated significantly more pull force than push force at 6-months post-surgery (p=0.025), but not at 3-months post-surgery (p=0.113) or pre-surgery (p=0.431). Table 23. Force data of two OA male pre- and post-surgery in the close, far and comfortable locations at the 0° wrist position Push 0° Close 0° Far 0° Comfortable Pre (N) 21.0 (12.2) 18.2 (3.4) 18.3 (10.8) 3 month 23.2 (8.6) 20.6 (7.7) 26.1 (11.0) 6 month Pull 24.8 (3.1) 26.1 (4.9) 25.8 (10.0) Pre 31.5 (19.4) 30.5 (17.6) 38.8 (25.0) 3 month 36.0 (16.0) 36.2 (19.9) 33.1 (16.7) 6 month 32.8 (0.11) 36.5 (6.0) 38.2 (8.4) Comparisons were also made between the healthy and OA groups at each time point. Pre-surgery, 3-months post-surgery, and 6-months post-surgery forces were all significantly less than OH females (push: p<0.047, pull: p<0.028), except for 6-month post-surgery compared to OH in the push direction (p=0.520). Pre-surgery, 3-months post-surgery, and 6-months post-surgery forces were all significantly less than YH females in the pull direction (p<0.043) but not in the push direction (p=0.988). On average, trends indicate the YH and OH males performed more force than the OA males at each time point. A significant difference was not found for the effect of peg location on force for OA participants. 83 4.4.5 90° Force Data Surgery Participant 90° Force Data ] N [ e c r o F t n a t l u s e R 50 45 40 35 30 25 20 15 10 5 0 push pull push pull push pull close far comfortable Pre- Pre- Surgery Surgery 3-months 3-months Post- Post- Surgery Surgery 6-months 6-months Post- Post- Surgery Surgery Push Push Pull Pull Figure 31. Average maximum force trials for CMC OA females (n=13) in the close, far and comfortable positions with 90° wrist position. For the 90° wrist position, the average maximum force pre- and post-surgery participants generated in the push and pull directions and in each location (close, far and comfortable) are shown in Figure 31. Table 24 shows the data for all female (n=13) surgery patients and Table 25 shows data for male (n=2) surgery patients. On average, OA female participants exerted more pull force than push force at all three time points, but the differences between push and pull at the three time points were not statistically significant within the OA group. Table 24. Average maximum thumb force data (standard deviation) for CMC OA females in each direction (push and pull) and location (close, far, and comfortable) in the 90° wrist position 3 month 6 month Pull 16.1 (6.0) Push 90° Close 90° Far 90° Comfortable Pre (N) 17.1 (8.9) 17.0 (8.6) 18.0 (9.0) 14.5 (6.0) 14.9 (8.0) 22.7 (9.7) 19.7 (7.0) 19.5 (8.4) 84 Pre 24.0 (9.0) 20.3 (7.8) 20.8 (8.9) 3 month 19.0 (7.8) 6 month 24.5 (8.7) 19.9 (6.4) 27.1 (8.2) 17.3 (9.7) 25.1 (10.0) Comparisons were made between the OA and healthy participants. At each time point (pre- surgery, 3- months, and 6- months post-surgery), OA female push forces were not significantly different from OH females. OA female pull forces were significantly less than the OH females at each time point (p<0.043), except for 6-months post-surgery (p=0.235). OA females 3-months post-surgery had significantly different pull forces than YH females (pull: p<0.004), but other time points were not significant compared to YH (push: p=0.974, pull: p=0.466). Table 25. Force data of two OA male pre- and post-surgery in the close, far and comfortable locations at a 90° wrist position Push 90° Close Pre (N) 3 month 25.6 (16.3) 19.7 (5.6) 90° Far 25.1 (10.4) 17.5 (4.6) 90° Comfortable 22.4 (14.6) 14.6 (2.3) 6 month Pull 22.4 (0.96) 23.0 (1.8) 20.7 (0.85) Pre 3 month 28.3 (18.4) 24.0 (7.1) 25.0 (12.2) 25.4 (9.1) 16.5 (13.1) 20.5 (9.7) 6 month 22.4 (2.2) 26.6 (3.9) 19.6 (1.2) In the OA female group, although pull was greater than push at all peg locations (close, far, and comfortable) at all three timepoints, these differences were not statistically significant. On average the YH and OH males performed more force than the OA males at each time point. Additionally, OA males showed decreased thumb force at 3-months post-surgery, increased force at 6-months post-surgery; however, they did not reach pre-surgery levels or those of healthy males. 4.4.6 Surgical Data Results Summary Individual force data sets of female OA patients pre-surgery were compared to 6-months post-surgery in each wrist position. As seen in Figure 32-43, groupings of female OA participants were made to identify an increase (>5 N), a decrease (> 5N), and no change in force abilities (< 5 N of pre-surgery force). Force data includes all locations (close, far, and comfortable), directions (push and pull), wrist position (0° an 90°), and timepoints (pre-surgery, 3- months, and 6- months post-surgery). In most cases, (both the 0° and 90° wrist positions) at least 5 OA females showed 85 improvement. However, the remainder (7 OA females) showed no change or a decrease in force abilities. In both the 0° and 90° wrist postures, all peg locations, and force directions, the average force generated by OA females and males showed a decrease at 3-months post-surgery compared to pre-surgery. Improvement of force generation was made by OA female participants 3-months to 6-months post-surgery (p<0.001) and pre to 6-months post-surgery (p<0.011) (Figure 30 and 31). More specifically, on average, OA females significantly increased force at 6-months post- surgery compared to 3-months post-surgery in the pull directions (p<0.002) but not the push direction (p=0.066). There were no significant differences in push versus pull in either the 0° or 90° wrist position for surgical participants. Overall, the effect of wrist position on force generation was considered to not be significant when group, force direction (push/pull), and location (close, comfortable, far) of force were combined for OA participants. 86 0° Close Push Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Push A7 A10 A12 A5 A9 A1 A15 A16 A11 A13 A17 A21 A14 ] N [ e c r o F t n a t l u s e R 60 50 40 30 20 10 0 Decreased >5 N No Change <5N Increased >5N Figure 32. Maximum force of two push trials for each CMC OA female (n=13) in the close location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. ] N [ e c r o F t n a t l u s e R 50 45 40 35 30 25 20 15 10 5 0 0° Close Pull Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull A1 A9 A13 A12 A5 A7 A15 A16 A10 A11 A14 A17 A21 Decreased >5 N No Change <5N Increased >5 N Figure 33. Maximum force of two pull trials for each CMC OA female (n=13) in the close location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 87 ] N [ e c o r F t n a t l u s e R 50 45 40 35 30 25 20 15 10 5 0 0° Far Pull Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull A7 A9 A1 A16 A5 A13 A12 A10 A11 A14 A15 A17 A21 Decreased >5N No Change <5N Increased > 5N Figure 34. Maximum force of two pull trials for each CMC OA female (n=13) in the far location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 0° Far Push ] N [ e c o r F t n a t l u s e R 50 45 40 35 30 25 20 15 10 5 0 Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Push A1 A12 A16 A5 A15 A9 A7 A17 A10 A11 A13 A21 A14 Decreased > 5N No Change <5N Increased > 5N Figure 35. Maximum force of two push trials for each CMC OA female (n=13) in the far location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 88 ] N [ e c r o F t n a t l u s e R 60 50 40 30 20 10 0 0° Comfortable Push Pre-Surgery 3-months Post- Surgery 6-months Post- Surgery Push A1 A5 A7 A9 A16 A15 A13 A12 A10 A11 A14 A17 A21 No Change <5N Decreased >5N Figure 36. Maximum force of two push trials for each CMC OA female (n=13) in the comfortable location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. Increased >5N Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull Decreased > 5N No Change <5N Increased > 5N Figure 37. Maximum force of two pull trials for each CMC OA female (n=13) in the comfortable location with 0° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 89 ] N [ e c r o F t n a t l u s e R 60 50 40 30 20 10 0 90° Close Push Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Push A12 A5 A1 A7 A9 A16 A11 A10 A13 A14 A15 A17 A21 Decreased > 5N No Change < 5N Increased >5 N Figure 38. Maximum force of two push trials for each CMC OA female (n=13) in the close location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre- surgery force) in thumb force pre– to 6-months post-surgery. Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull Decreased > 5N Increased >5 N Figure 39. Maximum force of two pull trials for each CMC OA female (n=13) in the close location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre- surgery force) in thumb force pre– to 6-months post-surgery. 90 ] N [ e c r o F t n a t l u s e R 60 50 40 30 20 10 0 90° Far Push Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Push A12 A7 A1 A16 A9 A5 A15 A21 A10 A11 A13 A14 A17 Decreased >5N No Change< 5N Increased >5N Figure 40. Maximum force of two push trials for each CMC OA females (n=13) in the far location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull Decreased >5N No Change< 5N Increased >5N Figure 41. Maximum force of two pull trials for each CMC OA females (n=13) in the far location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 91 90° Comfortable Push ] N [ e c o r F t n a t l u s e R 60 50 40 30 20 10 0 Pre- Surgery 3- months Post- Surgery 6- months Post- Surgery Push A1 A16 A12 A5 A9 A7 A21 A15 A10 A11 A13 A17 A14 Decreased >5N No Change <5N Increased >5N Figure 42. Maximum force of two push trials for each CMC OA female (n=13) in the comfortable location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. Pre- Surgery 3-months Post- Surgery 6-months Post- Surgery Pull Decreased >5N Increased >5N Figure 43. Maximum force of two pull trials for each CMC OA females (n=13) in the comfortable location with 90° wrist position. Participants that showed a decrease (greater than 5N), increase (greater than 5N) or no change (within 5N of pre-surgery force) in thumb force pre– to 6-months post-surgery. 92 4.4.7 Clinical Measurement Data Clinical measurements, grip strength, tip pinch and key pinch, were collected for all healthy and OA participants. Healthy participant data are shown in Table 26. YH males generated larger grip and pinch strength that OH males, but the difference was not statistically significant. OH females performed more grip and tip pinch strength compared to YH females but the results were also not statistically significant. Larger key pinch strength was performed by YH females compared to OH females, but again this was not found to be statistically significant. Table 26. Average healthy participant grip strength, tip and key pinch strength (standard deviation) Grip Strength (kg) Tip Pinch (kg) Key Pinch (kg) YH Females (n=13) 27.0 (6.2) 4.10 (1.1) 7.69 (1.4) OH Females (n=13) 27.8 (4.2) 4.37 (0.8) 7.34 (1.3) YH Males (n=13) 43.3 (12.4) 6.25 (0.9) 10.8 (2.2) OH Males (n=13) 42.8 (10.2) 5.76 (0.8) 10.7 (2.2) Grip strength, tip pinch, and key pinch are shown in Figures 44, 45, and 46, respectively, for OA females. In the OA female group, 5 individuals showed an increase in grip at the 6-month time point, 4 showed an increase in the tip pinch, and 5 showed an increase in key pinch strength. Grip strength performed by OA females was similar to values reported by other studies [3,208]. No statistical differences were found between each time point for all strength measurements. Table 27. Average grip strength, tip and key pinch strength (standard deviation) for OA males pre- surgery, 3-months, and 6-months post-surgery Pre OA Males (n=2) Grip Strength (kg) 34.3(21.3) 4.10 (1.1) Tip Pinch (kg) 7.69 (1.4) Key Pinch (kg) 3 months 27.8 (4.2) 4.37 (0.8) 7.34 (1.3) 6 months 43.3 (12.4) 6.25 (0.9) 10.8 (2.2) 93 Tip Pinch 6 5 4 3 2 1 0 ) g k ( h t g n e r t S A14 A1 A5 A12 A13 A7 A9 A10 A11 A15 A16 A17 A21 Figure 44. Tip pinch strength for OA females (n=13) pre-surgery, 3-months and 6- months post-surgery. Grip Strength ) g k ( h t g n e r t S 40 35 30 25 20 15 10 5 0 Pre 3mo 6mo Pre 3mo 6mo A5 A1 A14 A21 Figure 45. Grip strength for OA females (n=13) pre-surgery, 3-months, and 6- months post-surgery. A13 A12 A16 A10 A15 A17 A11 A7 A9 94 ) g k ( h t g n e r t S 12 10 8 6 4 2 0 Key Pinch Pre 3mo 6mo A14 A1 A5 A12 A13 A7 A9 A10 A11 A15 A16 A17 A21 Figure 46. Key pinch strength for OA females (n=13) pre-surgery, 3-months and 6- months post-surgery. A9 Thumb/Hand Strength 1.2 1 0.8 0.6 0.4 0.2 0 Pre 3 mo 6 mo Grip Tip Key Comf Push Comf Pull Figure 47. Normalized (by the largest value out of all three time points) grip strength, tip pinch, key pinch, and 0° deg comfortable push and pull performed. These data are for one OA female pre-surgery, 3-months, and 6-months post. Different trends across measurement techniques were noted. 95 Average OA Female Thumb/Hand Strength Pre 3 mo 6 mo 1.20 1.00 0.80 0.60 0.40 0.20 0.00 Grip Tip Key Comf push Comf pull Figure 48. Average grip strength, tip and key pinch strength, 0° deg comfortable push and pull performed for all OA females (normalized by the largest value out of all three time points) Different trends across measurement techniques were noted. A comparison of clinical measurements pre- and post-surgery to isolated thumb push and pull is depicted in Figure 48. Each strength measurement (grip strength, tip pinch, and key pinch, 0° comfortable thumb push and pull) was normalized by the largest value across time points. For example, each average value of grip strength at pre-surgery, 3-months, and 6-months post-surgery was normalized by the (largest) grip strength, which occurred at 6-months post-surgery. On average, these data showed OA female thumb and hand strength decreased at 3-months post- surgery, but increased force at 6-months post-surgery compared to pre-surgery. However, on average OA females performed less push and pull thumb forces pre-surgery compared to tip and key pinch strength pre-surgery, and therefore larger improvement was made at 6-months post- surgery as indicated by isolated thumb force. However, upon further investigation, not all participants showed the same trend. For example, Figure 47, which represents one OA female 96 participant’s normalized hand/digit strength and isolated thumb force, shows that at 6-months post- surgery, key pinch reached close to that of pre-surgery strength levels. However, isolated thumb pull forces showed a reduction in thumb force at 6-months post-surgery compared to pre-surgery. Furthermore, for OA participants tip pinch was found to be significantly larger in magnitude compared to 0° comfortable push force (p=0.036). Additionally, 0° comfortable pull force was significantly less than key pinch for OA participants (p=0.035). The average trend pre-surgery compared to post-surgery showed that isolated thumb push and pull were similar to grip strength, key pinch; however, not all participants individually demonstrated the trend identified with the average data. Thus, the comparisons between clinical measurement tools do not mimic the results from isolated thumb push and pull forces. 4.5 Discussion The goals of this study were to 1) determine and compare thumb force generation in younger and older healthy males and females without CMC OA to those diagnosed with CMC OA pre- and post- LRTI surgery, 2) compare thumb force generation at three time points (pre-surgery, 3-months post-surgery. and 6-months post-surgery) of those that have CMC OA, 3) determine the effect of wrist position on thumb force, 4) determine the differences between thumb force in the push direction versus a pull direction, and 5) identify the effects on thumb forces in different locations (close, far, and comfortable). 4.5.1 Thumb Force Generation Between Groups In this study, comparisons of force generation were made between all groups: YH, OH, and OA (pre-surgery, 3-months post-surgery, and 6-months post-surgery). Isolated thumb force data has not been extensively reported or compared in heathy individuals and those with CMC OA, particularly at multiple points in time related to surgery. The average difference between pre- 97 surgery and 6-months post-surgery force generation varied based on participant; however, only 50% of CMC OA participants showed greater than 5 N of improvement at 6-months post-surgery compared to pre-surgery and only one participant reached values of the OH average. Although force was not restored to the magnitude of healthy females, some CMC OA participants did see improvements in force generation 6-months post-surgery compared to pre-surgery. However, increases in strength levels are not likely to continue after 6-months as patients have ended rehabilitation and research suggests it is unlikely for them to continue their exercises [209]. As expected, on average, healthy (OH and YH) females generated statistically larger forces compared to the OA females pre-surgery. Although not significantly different, the trends showed that OH females generated larger thumb forces than YH females. Additionally, on average, OH male participants generated larger forces than the YH males, although this difference was also not statistically significant. This could be attributed to the fact that the OH individuals had significant work experience in some areas requiring manual labor, whereas the YH group was primarily comprised of college students with less work experience. 4.5.2 Push vs. Pull Force Data All participants, healthy (OH and YH) and arthritic (pre- and post-surgery), generated larger forces in the pull direction compared to the push direction. The pull position was similar to lateral pinch in which the thumb adducts towards the other four digits of the hand [63,158]. Muscles that assist in the isolated thumb pull (i.e., CMC flexion) direction are the abductors and flexors surrounding the CMC joint: the adductor pollicis, flexor pollicis longus and brevis, and abductor pollicis longus and brevis [210,211]. While both the flexor and abductor muscles were active in this motion, the flexors are the stronger of the muscles and highly engaged in the pull forces, while abductor muscles were mainly used as stabilizing muscles [210–212]. Based on this, there is a 98 larger functional advantage during thumb pull in comparison to thumb push. Furthermore, the thumb pull direction, or lateral pinch position, is performed in many ADLs such as holding a cup or key. Thus, these muscles are continually performing tasks in daily life [213]. Restoring strength to this particular thumb posture is important for individuals who received CMC OA surgery to maintain independent living. 4.5.3 Males vs Females Force Data With this extensive data set, data were compared between males and females. Results showed that, on average, healthy males had statistically larger thumb force than healthy females. This was true for both the YH group (males versus females) as well as the OH (males versus females) group, and was consistent with the literature [199,200,214]. It is known that men have more muscle mass than women, especially in their upper body [215–217]. Although it was not part of this data collection, historically, some men had occupations that required them to work with their hands, such as in factories, on construction sites, in landscaping, or in carpentry that could also contribute to the strength differences [218]. It is also important to note that only two OA males were included in this study. As noted earlier, data trends of the two OA males were not statistically compared to the OA females due to the small sample size. 4.5.4 Force Data as a Function of Location The main effect of peg location on force generation was found to be significant when all force data were grouped together (group, force direction, and wrist position). Force produced in the comfortable location was significantly different compared to the far location. On average, for most groups, the comfortable location produced more force (compared to the far and close location) and the far location produced less force (compared to the close and comfortable location). For the OH males specifically, a significant difference was found between the comfortable 99 compared and far locations. There was no significant difference found when performing force at one location compared to another for YH (males and females) and OH females. Additionally, no statistically significant differences were found between locations for the surgical group pre- surgery, or 3- or 6-months post-LRTI surgery. 4.5.5 0° vs 90° wrist position The effect of wrist position on force generation also produced mixed results based on the group. Overall, there were significant differences found when the force magnitudes in the 0° wrist position were compared to the 90° wrist position. Statistical analysis led to the conclusion that the 0° wrist position produced larger thumb force compared to the 90° wrist position. Other studies have shown that muscles produce their maximum amount of force in their fully lengthened position. [219–221]. Length of muscles attached at their various origin and insertion points at bony landmarks may become altered due to bone positioning, rotation, or bending [222,223]. Furthermore, a muscle is in its most lengthened position when the distance between its origin and insertion increases, i.e., when the muscle lengthens in the direction opposite to its action [219,224–226]. The muscles utilized to generate force (both push and pull) in both wrist positions are the opponens pollicis, the flexor and abductor pollicis longus and brevis, and the adductor pollicis longus [59,158,173,227,228]. Of these muscles listed, the flexor and abductor pollicis longus are the only two muscles assisting in thumb push and pull that originate on the forearm bones and insert onto the bones of the thumb. As the forearm and wrist pronate (from anatomical position), the flexor and abductor pollicis longus are maximally stretched, thus being in a position to produce maximal force. Furthermore, the thenar muscles (opponens policis, flexor and abductor pollicis brevis) are less stretched and do not cross the wrist, thus in theory the force generated by these muscles is not affected by wrist position. Therefore, in the 0° wrist position 100 (complete pronation of the forearm and wrist from the anatomical position), the two muscles crossing the wrist may assist in generating larger force in the 0° wrist position compared to the 90° wrist position. Since there were significant differences between the push and pull forces, an analysis of these motions was conducted to see the effects of wrist position on them. Thumb pull force performed in the 0° wrist position generated statistically larger forces compared to thumb pull in the 90° wrist. However, thumb push forces did not show significant differences between the two wrist positions. This difference with regard to wrist position and force direction could have been related to the muscles involved in these activities. The adductor pollicis was reported to be twice as active during lateral pinch (which is similar to pull), making it the dominant muscle along with the flexors, which contribute to the direction of applied force (i.e., pull towards the hand) [210]. Another study stated that the strongest strength achieved by the thumb are in a direction that bring the thumb towards the palm [211]. Additionally, some of the thenar muscles (flexor pollicis brevis and opponens pollcis) assist opposition or thumb pull, which may contribute to statistically larger forces produced during thumb pull than push. When considering just the force data in the 0° wrist position compared to the 90° wrist position (not direction or location) within each group, OH females were the only group to generate larger force in the 0° compared to 90° between the two wrist positions. While all groups experienced a change in muscle length and tension between the two wrist positions, it is important to note that only the OH female group is where a statistical difference in force generation occurred. The literature has shown ligament laxity around the CMC joint may be a precursor to developing CMC OA. Ligaments attach bone to bone, and at the CMC joint, ligaments attach the trapezium to the metacarpal. Thus, any alteration in ligament stability at the CMC joint may lead to an altered 101 force path, which changes the force abilities of the thumb. Furthermore, the OA participants pre- surgery did not show the same significance as the OH females. OA females pre-surgery already have compromised function and this loss of function was larger than changes associated with wrist orientation. Data for the three timepoints indicate that there were no significant differences in thumb force with wrist position, peg location, or direction across time points for OA females. These results revealed that after the removal of the trapezium, this anatomical change impacted force generation. Replacement of the trapezium with ligamentous soft tissue alters the load path and changes the ability to generate force at the level of healthy participants when certain tasks are performed. 4.5.6 Clinical Tools The outcomes of CMC OA surgery were measured with standard clinical tools including the dynamometer and pinch gauge. However, the data obtained here suggests that current clinical measurement tools mask changes in thumb force. Based on the results of the work presented here, on average, patients’ isolated thumb force decreased post-surgery; but the findings from the clinical tools did not yield the same results. The challenge with the clinical tools is that the thumb is not isolated, rather other digits were involved in each of the clinical measures. Isolated thumb forces were unique to this study and were able to be obtained through a novel measurement device. These data should be used over current methods to monitor progress of strength abilities after thumb surgery. Many studies in the literature reported that post-surgery thumb strength, using clinical tools, showed that patients improved compared to pre-surgery or near to that of their healthy contralateral side, but these data suggest this is not a true representation of thumb force abilities [34,184,185,229,230]. Thus, this research provides detailed insight into the thumb 102 strength; specifically, how much has been lost, gained, or restored post-surgery compared to pre- surgery and to the healthy population. 4.6 Limitations Participant activities (e.g., work, leisure) were not known and could have contributed to hand and thumb strength abilities. The occupation of each participant was recorded; however, many of the participants in the OH groups listed their occupation as “retired.” Comparisons of individuals pre- and post-surgery would not be impacted as these are comparisons within an individual. Another limitation is the effort in which participants generated force, as their goal was to generate their maximum amount of force. Thus, it is assumed that each participant was motivated to always produce their maximum level of force. The clinical standard measurement position of the dynamometer and pinch gauge is with the shoulder in neutral position, elbow flexed to 90, and the forearm and wrist in neutral. However, in this study, participants were measured with the elbow extended and shoulder at some degree of abduction which may have altered the strength levels generated for maximum grip and pinch strength of each individual. 4.7 Conclusions and Impact This study provided comprehensive data sets on isolated thumb force generation of healthy and arthritic groups post-LRTI surgery. Isolated thumb force has not been extensively reported in literature, especially for CMC OA individuals and when compared across time points. Data sets reported in this work provide new information to determine if function post-LRTI surgery is at the magnitude of healthy individuals. This work showed new insights into thumb force generation. A novel method was developed to identify isolated thumb forces at different thumb locations, direction of applied force, and wrist positions. Current clinical measurement tools do not include direction of force or wrist 103 position and their effect on thumb force. Furthermore, wrist position or direction of force has not been extensively reported in literature or has shown mixed results. These data allow surgeons to identify changes in force generation at a specific thumb postures, which is an improvement upon current clinical measurement tools as they mask thumb force by using other digits. Thus, these data sets reporting thumb force in different directions and wrist positions are new findings and important to consider when testing those with CMC OA pre- and post-surgery. 104 CONCLUSIONS The goal of this research was to better understand 3D thumb function and force abilities in young and older healthy individuals with and without a diagnosis of thumb CMC OA. This work aimed to determine the contribution of all joints of the thumb during complex motions. Additionally, this work focused on quantifying isolated thumb force generation. Complex thumb motion was analyzed, which provided a more thorough analysis compared to clinical goniometer. This new information has the potential to identify changes in function that could indicate higher risk for onset of CMC OA. Each joint of the thumb should be considered together when assessing thumb ROM of those with CMC OA. It is important to first understand healthy function to monitor treatment effects or design future therapies. Utilizing a more detailed analysis of thumb motion could provide additional information to clinicians to inform individuals to seek conservative treatment before they start experiencing pain or visual abnormalities. Further research could explore other motions of the thumb when interacting with other digits of the hand while performing daily tasks. A new, novel testing setup collected thumb force of healthy and arthritic groups. This testing setup isolated thumb force generation in different wrist positions and allowed for data collection in the push and pull force directions and comparisons of close, comfortable, and far locations. Thus, the current clinical methods to assess progress of thumb strength are not an accurate presentation of thumb force. These data will provide researchers and clinicians detailed insight into differences and commonalities that may be seen between the healthy and arthritic populations. Through baseline datasets of young healthy, older healthy, and OA ranges of motion, this work presents the foundation for future work to continue with the potential to establish differences in various types of surgical procedures or implants. Additionally, these data sets provide hand surgeons with more 105 detailed information to create personalized care in terms of therapies and exercises. Thus, these data could be used to improve clinical care and provide tailored treatment plans for those with CMC OA to determine if function is being restored. 106 REFERENCES [1] Clynes MA, Jameson KA, Edwards MH, Cooper C, Dennison EM. Impact of osteoarthritis on activities of daily living: does joint site matter? Aging Clin Exp Res 2019;31:1049–56. https://doi.org/10.1007/s40520-019-01163-0.[2] Kloppenburg M. Hand osteoarthritis - An increasing need for treatment and rehabilitation. Curr Opin Rheumatol 2007;19:179–83. https://doi.org/10.1097/BOR.0b013e32802106a8. [3] Bagis S, Sahin G, Yapici Y, Cimen OB, Erdogan C. The effect of hand osteoarthritis on grip and pinch strength and hand function in postmenopausal women. Clin Rheumatol 2003;22:420–4. https://doi.org/10.1007/s10067-003-0792-4. [4] Goldring MB, Goldring SR. Osteoarthritis. J Cell Physiol 2007;213:626–34. https://doi.org/10.1002/JCP.21258. [5] Dahaghin S, Bierma-Zeinstra SMA, Hazes JMW, Koes BW. Clinical burden of radiographic hand osteoarthritis: A systematic appraisal. Arthritis Care Res 2006;55:636– 47. https://doi.org/10.1002/art.22109. [6] Dickson RA, Morrison JD. The Pattern of Joint Involvement in Hands with Arthritis at the Base of the Thumb n.d. [7] [8] [9] Leung GJ, Rainsford KD, Kean WF. Osteoarthritis of the hand I: Aetiology and pathogenesis, risk factors, investigation and diagnosis. J Pharm Pharmacol 2014;66:339– 46. https://doi.org/10.1111/jphp.12196. Zhang Y, Niu J, Kelly-Hayes M, Chaisson CE, Aliabadi P, Felson DT. Prevalence of symptomatic hand osteoarthritis and its impact on functional status among the elderly: The framingham study. Am J Epidemiol 2002;156:1021–7. https://doi.org/10.1093/aje/kwf141. van der Oest MJW, Duraku LS, Andrinopoulou ER, Wouters RM, Bierma-Zeinstra SMA, Selles RW, et al. The prevalence of radiographic thumb base osteoarthritis: a meta- analysis. Osteoarthr Cartil 2021;29:785–92. https://doi.org/10.1016/j.joca.2021.03.004. [10] Dillon CF, Hirsch R, Rasch EK, Gu Q. Symptomatic hand osteoarthritis in the United States: Prevalence and functional impairment estimates from the third U.S. National Health and Nutrition Examination Survey, 1991-1994. Am J Phys Med Rehabil 2007;86:12–21. https://doi.org/10.1097/PHM.0b013e31802ba28e. [11] Kalichman L, Hernández-Molina G. Hand osteoarthritis: An epidemiological perspective. Semin Arthritis Rheum 2010;39:465–76. https://doi.org/10.1016/j.semarthrit.2009.03.001. [12] Dias R, Chandrasenan J, Rajaratnam V. Basal thumb arthritis. Postgr Med J 2007;83:40– 3. https://doi.org/10.1136/pgmj.2006.046300. 107 [13] Harra MM, Heliovaara M, Kroger H, Arokoski J, Manninen P. Osteoarthritis in the Carpometacarpal Joint of the Thumb. J Bone Joint Surg Am 2004;86-A. [14] Anakwe RE, Middleton SD. Osteoarthritis at the base of the thumb. BMJ 2011;343:1160– 6. https://doi.org/10.1136/bmj.d7122. [15] Bellamy N, Campbell J, Haraoui B, Buchbinder R, Hobby K, Roth JH, et al. Dimensionality and clinical importance of pain and disability in hand osteoarthritis: Development of the Australian/Canadian (AUSCAN) osteoarthritis hand index. Osteoarthr Cartil 2002;10:855–62. https://doi.org/10.1053/joca.2002.0837. [16] Panneerselvam D, Premalatha R. Digital photography for the diagnosis and grading of hand osteoarthritis 2020;19:45–53. https://doi.org/10.9790/0853-1904054553. [17] Patel TJ, Beredjiklian PK, Matzon JL. Trapeziometacarpal joint arthritis. Curr Rev Musculoskelet Med 2013;6:1–8. https://doi.org/10.1007/s12178-012-9147-6. [18] Kjeken I, Dagfinrud H, Slatkowsky-Christensen B, Mowinckel P, Uhlig T, Kvien TK, et al. Activity limitations and participation restrictions in women with hand osteoarthritis: Patients’ descriptions and associations between dimensions of functioning. Ann Rheum Dis 2005;64:1633–8. https://doi.org/10.1136/ard.2004.034900. [19] Neumann DA, Bielefeld T. The carpometacarpal joint of the thumb: stability, deformity, and therapeutic intervention. J Orthop Sports Phys Ther 2003;33:386–99. https://doi.org/10.2519/JOSPT.2003.33.7.386. [20] Sakalauskiene G, Jauniškiene D. Osteoarthritis: Etiology, epidemiology, impact on the individual and society and the main principles of management. Medicina (B Aires) 2010. https://doi.org/10.3390/medicina46110111. [21] Felson DT. Risk factors for osteoarthritis: Understanding joint vulnerability. Clin Orthop Relat Res 2004:16–21. https://doi.org/10.1097/01.blo.0000144971.12731.a2. [22] Normand M, Tang TS, Brismée JM, Sobczak S. Clinical evaluation of thumb base osteoarthritis: A scoping review. Hand Ther 2021;26:63–78. https://doi.org/10.1177/17589983211002560. [23] Gillis Bsc J, Calder Bsc K, Williams J. Review of thumb carpometacarpal arthritis classification, treatment and outcomes. vol. 19. 2011. [24] Estes JP, Bochenek C, Fasler P. Osteoarthritis of the fingers. J Hand Ther 2000;13:108– 23. https://doi.org/10.1016/S0894-1130(00)80035-6. [25] Bromann Bukhave E, Huniche L. Disability and Rehabilitation Activity problems in everyday life-patients’ perspectives of hand osteoarthritis: “try imagining what it would be like having no hands” Activity problems in everyday life-patients’ perspectives of hand 108 osteoarthritis:‘ “try imagining what it would be like having no hands.”’ Disabil Rehabil 2014;36:1636–43. https://doi.org/10.3109/09638288.2013.863390. [26] Chang JH, Ho KY, Su FC. Kinetic analysis of the thumb in jar-opening activity among female adults. Ergonomics 2008;51:843–57. https://doi.org/10.1080/00140130701763621. [27] Gracia-Ibáñez V, Vergara M, Sancho-Bru JL, Mora MC, Piqueras C. Functional range of motion of the hand joints in activities of the International Classification of Functioning, Disability and Health. J Hand Ther 2017;30:337–47. https://doi.org/10.1016/J.JHT.2016.08.001. [28] Swigart CR, Eaton RG, Glickel SZ, Johnson C. Splinting in the treatment of arthritis of the first carpometacarpal joint. J Hand Surg Am 1999;24:86–91. https://doi.org/10.1053/jhsu.1999.jhsu24a0086. [29] Higgenbotham C, Boyd A, Busch M, Heaton D, Trumble T. Optimal management of thumb basal joint arthritis: Challenges and solutions. Orthop Res Rev 2017;9:93–9. https://doi.org/10.2147/ORR.S138809. [30] Shuler MS, Luria S, Trumble TE. Basal joint arthritis of the thumb. J Am Acad Orthop Surg 2008;16:418–23. https://doi.org/10.5435/00124635-200807000-00007. [31] Yao J, Park MJ. Early Treatment of Degenerative Arthritis of the Thumb Carpometacarpal Joint. Hand Clin 2008;24:251–61. https://doi.org/10.1016/j.hcl.2008.03.001. [32] Tsehaie J, Spekreijse KR, Wouters RM, Feitz R, Hovius SER, Slijper HP, et al. Predicting Outcome After Hand Orthosis and Hand Therapy for Thumb Carpometacarpal Osteoarthritis: A Prospective Study. Arch Phys Med Rehabil 2019;100:844–50. https://doi.org/10.1016/J.APMR.2018.08.192. [33] deGroot Swanson G. Osteoarthritis in the hand. J Hand Surg Am 1983;8:669–75. https://doi.org/10.1016/S0363-5023(83)80242-1. [34] Gangopadhyay S, McKenna H, Burke FD, Davis TRC. Five- to 18-Year Follow-Up for Treatment of Trapeziometacarpal Osteoarthritis: A Prospective Comparison of Excision, Tendon Interposition, and Ligament Reconstruction and Tendon Interposition. J Hand Surg Am 2012;37:411–7. https://doi.org/10.1016/J.JHSA.2011.11.027. [35] Dhar S, Gray ICM, Jones WA, Beddow FH. SIMPLE EXCISION OF THE TRAPEZIUM FOR OSTEOARTHRITIS OF THE CARPOMETACARPAL JOINT OF THE THUMB. J Hand Surg Am 1994;19:485–8. [36] Kuhns CA, Emerson ET, Meals RA. Hematoma and distraction arthroplasty for thumb basal joint osteoarthritis: A prospective, single-surgeon study including outcomes measures. J Hand Surg Am 2003;28:381–9. https://doi.org/10.1053/JHSU.2003.50078. 109 [37] Shonuga O, Nicholson K, Abboudi J, Gallant G, Jones C, Kirkpatrick W, et al. Thumb- Basal Joint Arthroplasty Outcomes and Metacarpal Subsidence: A Prospective Cohort Analysis of Trapeziectomy With Suture Button Suspensionplasty Versus Ligament Reconstruction With Tendon Interposition. Hand 2021. https://doi.org/10.1177/1558944721994227. [38] Ellis B, Bruton A, Goddard JR. Joint angle measurement: A comparative study of the reliability of goniometry and wire tracing for the hand. Clin Rehabil 1997;11:314–20. https://doi.org/10.1177/026921559701100408. [39] Ellis B, Bruton A. Clinical Assessment of the Hand - A Review of Joint Angle Measures: Http://DxDoiOrg/101177/175899839800300204 2016;3:5–8. https://doi.org/10.1177/175899839800300204. [40] Kato M, Echigo A, Ohta H, Ishiai S, Aoki M, Tsubota S, et al. The Accuracy of Goniometric Measurements of Proximal Interphalangeal Joints in Fresh Cadavers: Comparison between Methods of Measurement, Types of Goniometers, and Fingers n.d. https://doi.org/10.1197/j.jht.2006.11.015. [41] Groth GN, VanDeven KM, Phillips EC, Ehretsman RL. Goniometry of the proximal and distal interphalangeal joints, part II: Placement preferences, interrater reliability, and concurrent validity. J Hand Ther 2001;14:23–9. https://doi.org/10.1016/S0894- 1130(01)80021-1. [42] Cook JR, Baker NA, Cham R, Hale E, Redfern MS. Measurements of Wrist and Finger Postures: A Comparison of Goniometric and Motion Capture Techniques. J Appl Biomech 2007;23:70–8. https://doi.org/10.1123/JAB.23.1.70. [43] Hamilton GF, Lachenbruch PA. Reliability of goniometers in assessing finger joint angle. Phys Ther 1969;49:465–9. https://doi.org/10.1093/ptj/49.5.465. [44] OA Prevalence & Burden Osteoarthritis Prevention and Management in Primary Care. 2019. [45] Dahaghin S, Bierma-Zeinstra SMA, Ginai AZ, Pols HAP, Hazes JMW, Koes BW. Prevalence and pattern of radiographic hand osteoarthritis and association with pain and disability (the Rotterdam study). Ann Rheum Dis 2005;64:682–7. https://doi.org/10.1136/ard.2004.023564. [46] Balasubramanian R, Santos VJ. The Human Hand as an Inspiration for Robot Hand Development n.d. [47] Badley EM. The impact of disabling arthritis. Arthritis Rheum 1995;8:221–8. https://doi.org/10.1002/ART.1790080405. [48] Hootman JM, Helmick CG, Barbour KE, Theis KA, Boring MA. Updated Projected 110 Prevalence of Self-Reported Doctor-Diagnosed Arthritis and Arthritis-Attributable Activity Limitation Among US Adults, 2015–2040. Arthritis Rheumatol 2016;68:1582–7. https://doi.org/10.1002/art.39692. [49] Vocelle AR, Shafer G, Bush TR. Complex thumb motions and their potential clinical value in identifying early changes in function. Clin Biomech 2020;73:63–70. https://doi.org/10.1016/j.clinbiomech.2020.01.004. [50] Matullo KS, Ilyas A, Thoder JJ. CMC arthroplasty of the thumb: A review. Hand 2007;2:232–9. https://doi.org/10.1007/s11552-007-9068-9. [51] Fautrel B, Hilliquin P, Rozenberg S, Allaert FA, Coste P, Leclerc A, et al. Impact of osteoarthritis: results of a nationwide survey of 10,000 patients consulting for OA. Jt Bone Spine 2005;72:235–40. https://doi.org/10.1016/J.JBSPIN.2004.08.009. [52] Gottschalk MB, Patel NN, Boden AL, Kakar S. Treatment of Basilar Thumb Arthritis: A Critical Analysis Review. JBJS Rev 2018;6:e4. https://doi.org/10.2106/JBJS.RVW.17.00156. [53] Jarque-Bou NJ, Vergara M, Sancho-Bru JL. Estimation of the abduction/adduction movement of the metacarpophalangeal joint of the thumb. Appl Sci 2021;11. https://doi.org/10.3390/APP11073158. [54] Riddle M, MacDermid J, Robinson S, Szekeres M, Ferreira L, Lalone E. Evaluation of individual finger forces during activities of daily living in healthy individuals and those with hand arthritis. J Hand Ther 2020;33:188–97. https://doi.org/10.1016/j.jht.2020.04.002. [55] Ladd AL, Weiss APC, Crisco JJ, Hagert E, Wolf JM, Glickel SZ, et al. The thumb carpometacarpal joint: anatomy, hormones, and biomechanics. Instr Course Lect 2013;62:165–79. [56] Moran SL, Berger RA. Biomechanics and hand trauma: what you need. Hand Clin 2003;19:17–31. https://doi.org/10.1016/S0749-0712(02)00130-0. [57] Cooney WP, Lucca MJ, Chao EY, Linscheid RL. The kinesiology of the thumb trapeziometacarpal joint. This Is an Enhanc PDF from J Bone Jt Surg 1981;63:1371–81. [58] Eaton RG, Glickel SZ. Trapeziometacarpal Osteoarthritis: Staging as a Rationale for Treatment. Hand Clin 1987;3:455–69. https://doi.org/10.1016/S0749-0712(21)00761-7. [59] Edmunds JO. Current concepts of the anatomy of the thumb trapeziometacarpal joint. J Hand Surg Am 2011;36:170–82. https://doi.org/10.1016/j.jhsa.2010.10.029. [60] Barmakian JT. Anatomy of the joints of the thumb. Hand Clin 1992;8:683–91. https://doi.org/10.1016/s0749-0712(21)00735-6. 111 [61] Pellegrini VD. Osteoarthritis of the trapeziometacarpal joint: The pathophysiology of articular cartilage degeneration. I. Anatomy and pathology of the aging joint. J Hand Surg Am 1991;16:967–74. https://doi.org/10.1016/S0363-5023(10)80054-1. [62] Pellegrini VD. The ABJS 2005 Nicolas Andry Award: Osteoarthritis and injury at the base of the human thumb - Survival of the fittest? Clin Orthop Relat Res 2005:266–76. https://doi.org/10.1097/01.blo.0000176968.28247.5c. [63] Toft R, Berme N. A biomechanical analysis of the joints of the thumb. J Biomech 1980;13:353–60. https://doi.org/10.1016/0021-9290(80)90015-9. [64] Pieron AP. The Mechanism of the First Carpometacarpal (CMC) Joint: An Anatomical and Mechanical Analysis. Acta Orthop Scand 1973;44:148–9. https://doi.org/10.3109/ort.1973.44.suppl-148.01. [65] Strauch RJ, Behrman MJ, Rosenwasser MP. Acute dislocation of the carpometacarpal joint of the thumb: An anatomic and cadaver study. J Hand Surg Am 1994;19:93–8. https://doi.org/10.1016/0363-5023(94)90229-1. [66] Jonsson P, Johnson PW, Johnson{ PW, Hagberg{ M. Accuracy and feasibility of using an electrogoniometer for measuring simple thumb movements 2007. https://doi.org/10.1080/00140130601164490. [67] Hamann N, Heidemann J, Heinrich K, Wu H, Bleuel J, Gonska C, et al. Stabilization effectiveness and functionality of different thumb orthoses in female patients with first carpometacarpal joint osteoarthritis. Clin Biomech 2014;29:1170–6. https://doi.org/10.1016/j.clinbiomech.2014.09.007. [68] Grenier ML, Mendonca R, Dalley P. The effectiveness of orthoses in the conservative management of thumb CMC joint osteoarthritis: An analysis of functional pinch strength. J Hand Ther 2016;29:307–13. https://doi.org/10.1016/j.jht.2016.02.004. [69] Barron, O, Glickel, Steven, Eaton R. Basal Joint Arthritis of the Thumb. J Am Acad Orthop Surg 2008;8:314–23. [70] Swigart CR. Arthritis of the base of the thumb. Curr Rev Musculoskelet Med 2008;1:142– 6. https://doi.org/10.1007/s12178-008-9022-7. [71] McVeigh KH, Murray PM, Heckman MG, Rawal B, Peterson JJ. Accuracy and Validity of Goniometer and Visual Assessments of Angular Joint Positions of the Hand and Wrist. J Hand Surg Am 2016;41:e21–35. https://doi.org/10.1016/j.jhsa.2015.12.014. [72] Bertozzi L, Valdes K, Vanti C, Negrini S, Pillastrini P, Hugo Villafañe J, et al. Disability and Rehabilitation Investigation of the effect of conservative interventions in thumb carpometacarpal osteoarthritis: systematic review and meta-analysis Investigation of the 112 effect of conservative interventions in thumb carpometacarpal osteoarthritis: systematic review and meta-analysis. Disabil Rehabil 2015;37:2025–43. https://doi.org/10.3109/09638288.2014.996299. [73] Villafañe JH, Valdes K, Bertozzi L, Negrini S. Minimal clinically important difference of grip and pinch strength in women with thumb carpometacarpal osteoarthritis when compared to healthy subjects. Rehabil Nurs 2017;42:139–45. https://doi.org/10.1002/rnj.196. [74] Meenagh GK, Patton J, Kynes C. A randomised controlled trial of intra-articular corticosteroid injection of the carpometacarpal joint of the thumb in osteoarthritis. Ann Rheum Dis 2004;63:1260–3. https://doi.org/10.1136/ard.2003.015438. [75] Day CS, Gelberman R, Patel AA, Vogt MT, Ditsios K, Boyer MI. Basal joint osteoarthritis of the thumb: a prospective trial of steroid injection and splinting. J Hand Surg Am 2004;29:247–51. https://doi.org/10.1016/J.JHSA.2003.12.002. [76] Khan M, Waseem M, Raza A, Derham D. Quantitative Assessment of Improvement with Single Corticosteroid Injection in Thumb CMC Joint Osteoarthritis? Open Orthop J 2009;3:48–51. [77] Groth GN, Ehretsman RL. Goniometry of the proximal and distal interphalangeal joints, part I: A survey of instrumentation and placement preferences. J Hand Ther 2001;14:18– 22. https://doi.org/10.1016/S0894-1130(01)80020-X. [78] de Carvalho RMF, Mazzer N, Barbieri CH. Analysis of the reliability and reproducibility of goniometry compared to hand photogrammetry. Acta Ortop Bras 2012;20:139–49. https://doi.org/10.1590/S1413-78522012000300003. [79] Fish DR, Wingate L. Sources of Goniometric Error at the Elbow n.d. [80] Mitobe K, Saitoh M, Yoshimura N. Analysis of dexterous finger movements for writing using a hand motion capture system. VECIMS 2010 - 2010 IEEE Int Conf Virtual Environ Human-Computer Interfaces Meas Syst Proc 2010:60–3. https://doi.org/10.1109/VECIMS.2010.5609351. [81] Kuo LC, Cooney WP, Oyama M, Kaufman KR, Su FC, An KN. Feasibility of using surface markers for assessing motion of the thumb trapeziometacarpal joint. Clin Biomech 2003;18:558–63. https://doi.org/10.1016/S0268-0033(03)00074-3. [82] Tanashi A, Haddara R, Haddara MM, Ferreira L, Lalone E. A method for measuring in vivo finger kinematics using electromagnetic tracking. Comput Methods Biomech Biomed Engin 2021. https://doi.org/10.1080/10255842.2021.2007375/FORMAT/EPUB. [83] Serra López VM, Gandhi RA, Falk DP, Baxter JR, Lien JR, Gray BL. Dynamic Thumb Circumduction Measured With a Wearable Motion Sensor: A Prospective Comparison of 113 Patients With Basal Joint Arthritis to Controls. J Hand Surg Glob Online 2021;3:190–4. https://doi.org/10.1016/j.jhsg.2021.05.002. [84] Chèze L, Doriot N, Eckert M, Rumelhart C, Comtet JJ. Étude cinématique in vivo de l’articulation trapézométacarpienne. Chir Main 2001;20:23–30. https://doi.org/10.1016/S1297-3203(01)00011-7. [85] Crisco JJ, Halilaj E, Moore DC, Patel T, Weiss APC, Ladd AL. In Vivo Kinematics of the Trapeziometacarpal Joint During Thumb Extension-Flexion and Abduction-Adduction. J Hand Surg Am 2015;40:289–96. https://doi.org/10.1016/J.JHSA.2014.10.062. [86] Cheema TA, Cheema NI, Tayyab R, Firoozbakhsh K. Measurement of Rotation of the First Metacarpal During Opposition Using Computed Tomography. J Hand Surg Am 2006;31:76–9. https://doi.org/10.1016/J.JHSA.2005.08.016. [87] Rash GS, Belliappa PP, Wachowiak MP, Somia NN, Gupta A. A demonstration of the validity of a 3-D video motion analysis method for measuring finger flexion and extension. J Biomech 1999;32:1337–41. https://doi.org/10.1016/S0021-9290(99)00140-2. [88] Nataraj R, Li ZM. Integration of marker and force data to compute three-dimensional joint moments of the thumb and index finger digits during pinch. Comput Methods Biomech Biomed Engin 2015;18:592–606. https://doi.org/10.1080/10255842.2013.820722. [89] Gehrmann S V., Tang J, Li ZM, Goitz RJ, Windolf J, Kaufmann RA. Motion deficit of the thumb in CMC joint arthritis. J Hand Surg Am 2010;35:1449–53. https://doi.org/10.1016/j.jhsa.2010.05.026. [90] Drost JP, Hong HG, Bush TR. Mapping Together Kinetic and Kinematic Abilities of the Hand 2020. https://doi.org/10.1115/1.4044141. [91] Reissner L, Fischer G, List R, Giovanoli P, Calcagni M. Assessment of hand function during activities of daily living using motion tracking cameras: A systematic review. Proc Inst Mech Eng Part H J Eng Med 2019;233:764–83. https://doi.org/10.1177/0954411919851302. [92] Goubier JN, Devun L, Mitton D, Lavaste F, Papadogeorgou E. Normal range-of-motion of trapeziometacarpal joint. Chir Main 2009;28:297–300. https://doi.org/10.1016/j.main.2009.07.003. [93] Sancho-Bru JL, Jarque-Bou NJ, Vergara M, Pérez-González A. Validity of a simple videogrammetric method to measure the movement of all hand segments for clinical purposes. Proc Inst Mech Eng Part H J Eng Med 2014;228:182–9. https://doi.org/10.1177/0954411914522023. [94] Reissner L, Fischer G, List R, Taylor WR, Giovanoli P, Calcagni M. Minimal detectable difference of the finger and wrist range of motion: Comparison of goniometry and 3D 114 motion analysis. J Orthop Surg Res 2019;14:1–10. https://doi.org/10.1186/s13018-019- 1177-y. [95] Goislard de Monsabert B, Vigouroux L, Bendahan D, Berton E. Quantification of finger joint loadings using musculoskeletal modelling clarifies mechanical risk factors of hand osteoarthritis. Med Eng Phys 2014;36:177–84. https://doi.org/10.1016/j.medengphy.2013.10.007. [96] Kuo L-C, Chang J-H, Lin C-F, Hsu H-Y, Ho K-Y, Su F-C. Jar-opening challenges. Part 2: estimating the force-generating capacity of thumb muscles in healthy young adults during jar-opening tasks n.d. https://doi.org/10.1243/09544119JEIM504. [97] Vigouroux L, Domalain M, Berton E. Effect of object width on muscle and joint forces during thumb - Index finger grasping. J Appl Biomech 2011;27:173–80. https://doi.org/10.1123/jab.27.3.173. [98] Luker KR, Aguinaldo A, Kenney D, Cahill-Rowley K, Ladd AL. Functional task kinematics of the thumb carpometacarpal joint. Clin Orthop Relat Res 2014;472:1123–9. https://doi.org/10.1007/s11999-013-2964-0. [99] An KN, Chao EY, Cooney WP, Linscheid RL. Forces in the normal and abnormal hand. J Orthop Res 1985;3:202–11. https://doi.org/10.1002/jor.1100030210. [100] Mruk JJ. Thumn IP, MCP, and MC Joint ROM in the Well Elderly Between the Ages of 60 and 90. Ann Arbor, MI: 1999. [101] Yoshida R, House HO, Patterson RM, Shah MA, Viegas SF. Motion and morphology of the thumb metacarpophalangeal joint. J Hand Surg Am 2003;28:753–7. https://doi.org/10.1016/S0363-5023(03)00303-4. [102] Hume MC, Gellman H, McKellop H, Brumfield RH. Functional range of motion of the joints of the hand. J Hand Surg Am 1990;15:240–3. https://doi.org/10.1016/0363- 5023(90)90102-W. [103] Li ZM, Tang J. Coordination of thumb joints during opposition. J Biomech 2007;40:502– 10. https://doi.org/10.1016/J.JBIOMECH.2006.02.019. [104] Hoppenffeld S. Propedêutica ortopédica: coluna e extremidades | São Paulo; Atheneu; 1999. 276 p. ilus, tab. | SMS-SP | SMS-SP | AHM-Acervo | CAMPOLIMPO-Acervo 1999. https://pesquisa.bvsalud.org/portal/resource/en/sms-2616 (accessed May 2, 2022). [105] Oliverira LM AP. Medida da amplitude articular. In: Sociedade Brasileira de Terapeutas de Maao, organizadores. Recomendacoes para avaliacao de membro superior. Soc Bras Ter Mao 2003:37–49. [106] Marques A. Manual de Goniometria - Amélia Pasqual Marques - Google Books 2002. 115 https://books.google.com/books?hl=en&lr=&id=hV0iCgAAQBAJ&oi=fnd&pg=PT3&ots =YPzzuO-8ab&sig=z9AEgBKiML1xl9Dp7FN5_yJkNn4#v=onepage&q&f=false (accessed May 2, 2022). [107] Barakat MJ, Field J, Taylor J. The range of movement of the thumb. Hand 2013;8:179–82. https://doi.org/10.1007/s11552-013-9492-y. [108] Jenkins M, Bamberger HB, Black L, Nowinski R. Thumb joint flexion: What is normal? J Hand Surg Eur Vol 1998;23. https://doi.org/10.1016/S0266-7681(98)80100-9. [109] JOSEPH J. Further studies of the metacarpo-phalangeal and interphalangeal joints of the thumb. J Anat 1951;85:221–9. [110] Shaw SJ, Morris MA. THE RANGE OF MOTION OF THE METACARPO- PHALANGEAL JOINT OF THE THUMB AND ITS RELATIONSHIP TO INJURY From the Stockport Infirmary n.d. [111] de Kraker M, Selles RW, Schreuders TAR, Stam HJ, Hovius SER. Palmar Abduction: Reliability of 6 Measurement Methods in Healthy Adults. J Hand Surg Am 2009;34:523– 30. https://doi.org/10.1016/J.JHSA.2008.10.028. [112] Dormitorio B, Hattori Y, Yukata K, Sakamoto S, Doi K. The use of dynamic radiographs in trapeziometacarpal joint arthrodesis for accurate range of motion evaluation. J Orthop Sci 2018;23:75–80. https://doi.org/10.1016/j.jos.2017.09.022. [113] Holzbauer M, Hopfner M, Haslhofer D, Kwasny O, Duscher D, Froschauer SM. Radial and palmar active range of motion measurement: reliability of six methods in healthy adults. J Plast Surg Hand Surg 2021;55:41–7. https://doi.org/10.1080/2000656X.2020.1828899. [114] Kimura T, Takai H, Azuma T, Sairyo K. Motion Analysis of the Trapeziometacarpal Joint Using Three-dimensional Computed Tomography. J Hand Surg Asian-Pacific Vol 2016;21:78–84. https://doi.org/10.1142/S2424835516500120. [115] Miura T, Ohe T, Masuko T. Comparative in vivo kinematic analysis of normal and osteoarthritic trapeziometacarpal joints. J Hand Surg Am 2004;29:252–7. https://doi.org/10.1016/J.JHSA.2003.11.002. [116] Kuroiwa T, Fujita K, Nimura A, Miyamoto T, Sasaki T, Okawa A. A new method of measuring the thumb pronation and palmar abduction angles during opposition movement using a three-axis gyroscope. J Orthop Surg Res 2018;13:17–21. https://doi.org/10.1186/s13018-018-0999-3. [117] Leitkam ST, Bush TR. Comparison between Healthy and Reduced Hand Function Using Ranges of Motion and a Weighted Fingertip Space Model. J Biomech Eng 2015;137. https://doi.org/10.1115/1.4029215. 116 [118] Hayashi M, Kato H, Komatsu M, Yamazaki H, Uchiyama S, Takahashi J. Changes in the Functional Range of Motion of the Thumb Metacarpophalangeal Joint After Trapeziometacarpal Arthrodesis for Patients With Advanced Trapeziometacarpal Osteoarthritis. J Hand Surg Am 2021:1–8. https://doi.org/10.1016/j.jhsa.2021.09.018. [119] Goubier J-N, Devun L, Mitton D, Lavaste F. In vivo trapeziometacarpal joint kinematics using an optoelectronic system : a data basis on healthy subjects. Ninth Symp 3D Anal Hum Mov 2006. [120] Lin HT, Kuo LC, Liu HY, Wu WL, Su FC. The three-dimensional analysis of three thumb joints coordination in activities of daily living. Clin Biomech 2011;26:371–6. https://doi.org/10.1016/j.clinbiomech.2010.11.009. [121] Nataraj R, Li ZM. Robust identification of three-dimensional thumb and index finger kinematics with a minimal set of markers. J Biomech Eng 2013;135:1–9. https://doi.org/10.1115/1.4024753. [122] Hatta T, Giambini H, Sukegawa K, Yamanaka Y, Sperling JW, Steinmann SP, et al. Quantified mechanical properties of the deltoid muscle using the shear wave elastography: Potential implications for reverse shoulder arthroplasty. PLoS One 2016;11. https://doi.org/10.1371/journal.pone.0155102. [123] Jarque-Bou NJ, Vergara M, Sancho-Bru JL, Gracia-Ibanez V, Roda-Sales A. Hand Kinematics Characterization while Performing Activities of Daily Living through Kinematics Reduction. IEEE Trans Neural Syst Rehabil Eng 2020;28:1556–65. https://doi.org/10.1109/TNSRE.2020.2998642. [124] Sakai N, Shimawaki S. Motion analysis of thumb in cellular phone use. Appl Bionics Biomech 2010;7:119–22. https://doi.org/10.1080/11762320903239462. [125] Gustafsson E, Johnson PW, Hagberg M. Thumb postures and physical loads during mobile phone use – A comparison of young adults with and without musculoskeletal symptoms. J Electromyogr Kinesiol 2010;20:127–35. https://doi.org/10.1016/J.JELEKIN.2008.11.010. [126] Baker NA, Cham R, Cidboy EH, Cook J, Redfern MS. Kinematics of the fingers and hands during computer keyboard use. Clin Biomech 2007;22:34–43. https://doi.org/10.1016/J.CLINBIOMECH.2006.08.008. [127] Bazański T. Metacarpophalangeal joints kinematics during a grip of everyday objects using three dimensional motion analysis system 2006:39–40. [128] Fowler NK, Nicol AC. Functional and biomechanical assessment of the normal and rheumatoid hand. Clin Biomech 2001;16:660–6. https://doi.org/10.1016/S0268- 0033(01)00057-2. 117 [129] Spörri J, Kröll J, Fasel B, Aminian K, Müller E. Course Setting as a Prevention Measure for Overuse Injuries of the Back in Alpine Ski Racing: A Kinematic and Kinetic Study of Giant Slalom and Slalom. Orthop J Sport Med 2016;4. https://doi.org/10.1177/2325967116630719. [130] D’Agostino P, Dourthe B, Kerkhof F, Harry Van Lenthe G, Stockmans F, Vereecke EE. In vivo biomechanical behavior of the trapeziometacarpal joint in healthy and osteoarthritic subjects. Clin Biomech 2017;49:119–27. https://doi.org/10.1016/J.CLINBIOMECH.2017.09.006. [131] Coert JH, van Dijke GAH, Hovius SER, Snijders CJ, Meek MF. Quantifying thumb rotation during circumduction utilizing a video technique. J Orthop Res 2003. https://doi.org/10.1016/S0736-0266(03)00114-1. [132] Glasoe WM, Pena FA, Phadke V. Cardan angle rotation sequence effects on first- metatarsophalangeal joint kinematics: Implications for measuring hallux valgus deformity. J Foot Ankle Res 2014;7:4–8. https://doi.org/10.1186/1757-1146-7-29. [133] López-Pascual J, Cáceres ML, De Rosario H, Page Á. The reliability of humerothoracic angles during arm elevation depends on the representation of rotations. J Biomech 2016;49:502–6. https://doi.org/10.1016/J.JBIOMECH.2015.12.045. [134] List R, Gülay T, Stoop M, Lorenzetti S, List Renate. Kinematics of the Trunk and the L Ower. J Strength Cond Res 2013;27:1529–38. [135] Rg Spö J, Krö J, Haid C, Fasel B, Mü E. Potential Mechanisms Leading to Overuse Injuries of the Back in Alpine Ski Racing A Descriptive Biomechanical Study n.d. https://doi.org/10.1177/0363546515588178. [136] Li J, Wyss UP, Costigan PA, Deluzio KJ. An integrated procedure to assess knee-joint kinematics and kinetics during gait using an optoelectric system and standardized X-rays. J Biomed Eng 1993;15:392–400. https://doi.org/10.1016/0141-5425(93)90076-B. [137] Fasel B, Spörri J, Schütz P, Lorenzetti S, Aminian K. Validation of functional calibration and strap-down joint drift correction for computing 3D joint angles of knee, hip, and trunk in alpine skiing. PLoS One 2017;12:e0181446. https://doi.org/10.1371/JOURNAL.PONE.0181446. [138] Neumann EE, Owings TM, Erdemir A. Regional variations of in vivo surface stiffness of soft tissue layers of musculoskeletal extremities. J Biomech 2019;95. https://doi.org/10.1016/j.jbiomech.2019.08.001. [139] Ricci FPFM, Santiago PRP, Zampar AC, Pinola LN, Fonseca M de CR. Upper extremity coordination strategies depending on task demand during a basic daily activity. Gait Posture 2015;42:472–8. https://doi.org/10.1016/j.gaitpost.2015.07.061. 118 [140] Goldstein, Herbert, Poole, Charles, Safko J. Classical Mechanics. 3rd ed. Addison Wesley; n.d. [141] Winter DA. Biomechanics and motor control of human movement. Wiley; 2009. [142] Halilaj E, Moore DC, Laidlaw DH, Got CJ, Weiss APC, Ladd AL, et al. The morphology of the thumb carpometacarpal joint does not differ between men and women, but changes with aging and early osteoarthritis. J Biomech 2014;47:2709–14. https://doi.org/10.1016/J.JBIOMECH.2014.05.005. [143] Tang J, Zhang X, Li ZM. Operational and maximal workspace of the thumb. Ergonomics 2008;51:1109–18. https://doi.org/10.1080/00140130801958667. [144] Fukuchi RK, Fukuchi CA, Duarte M. A public dataset of running biomechanics and the effects of running speed on lower extremity kinematics and kinetics. PeerJ 2017;2017:3298. https://doi.org/10.7717/PEERJ.3298. [145] Zuk M, Pezowicz C. Kinematic analysis of a six-degrees-of-freedom model based on ISB recommendation: A repeatability analysis and comparison with conventional gait model. Appl Bionics Biomech 2015;2015:1–10. https://doi.org/10.1155/2015/503713. [146] Halilaj E, Rainbow MJ, Got CJ, Moore DC, Crisco JJ. A thumb carpometacarpal joint coordinate system based on articular surface geometry. J Biomech 2013;46:1031–4. https://doi.org/10.1016/j.jbiomech.2012.12.002. [147] Orlando MF, Dutta A, Saxena A, Behera L, Tamei T, Shibata T. Manipulability analysis of human thumb, index and middle fingers in cooperative 3D rotational movements of a small object. Robotica 2013;31:797–809. https://doi.org/10.1017/S0263574713000064. [148] Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three- dimensional motions: Application to the knee. J Biomech Eng 1983;105:136–44. https://doi.org/10.1115/1.3138397. [149] Hillstrom HJ, Garg R, Kraszewski A, Lenhoff M, Carter T, Backus SI, et al. Development of an anatomical wrist joint coordinate system to quantify motion during functional tasks. J Appl Biomech 2014;30:586–93. https://doi.org/10.1123/jab.2011-0094. [150] Desroches G, Chèze L, Dumas R. Expression of joint moment in the joint coordinate system. J Biomech Eng 2010;132:1–4. https://doi.org/10.1115/1.4002537. [151] Pennock GR, Clark KJ. An anatomy-based coordinate system for the description of the kinematic displacements in the human knee. J Biomech 1990;23:1209–18. https://doi.org/10.1016/0021-9290(90)90378-G. 119 [152] Dumas R, Chèze L. 3D inverse dynamics in non-orthonormal segment coordinate system. Med Biol Eng Comput 2007;45:315–22. https://doi.org/10.1007/s11517-006-0156-8. [153] Van Hauwermeiren L, Verstraete M, Stouthandel MEJ, Van Oevelen A, De Gersem W, Delrue L, et al. Joint coordinate system for biomechanical analysis of the sacroiliac joint. J Orthop Res 2019;37:1101–9. https://doi.org/10.1002/jor.24271. [154] Rouhani H, Favre J, Crevoisier X, Jolles BM, Aminian K. A comparison between joint coordinate system and attitude vector for multi-segment foot kinematics. J Biomech 2012;45:2041–5. https://doi.org/10.1016/j.jbiomech.2012.05.018. [155] Hollister A, Giurintano DJ. Thumb Movements, Motions, and Moments. J Hand Ther 1995;8:106–14. https://doi.org/10.1016/S0894-1130(12)80307-3. [156] Hollister A, Buford WL, Myers LM, Giurintano DJ, Novick A. The axes of rotation of the thumb carpometacarpal joint. J Orthop Res 1992;10:454–60. https://doi.org/10.1002/JOR.1100100319. [157] Batra S, Kanvinde R. Osteoarthritis of the thumb trapeziometacarpal joint. Curr Orthop 2007;21:135–44. https://doi.org/10.1016/j.cuor.2007.02.006. [158] Imaeda T, An KN, Cooney WP. Functional anatomy and biomechanics of the thumb. Hand Clin 1992. [159] Imaeda T, Niebur G, Cooney WP, Linscheid RL, An K ‐N. Kinematics of the normal trapeziometacarpal joint. J Orthop Res 1994;12:197–204. https://doi.org/10.1002/JOR.1100120208. [160] Leijnse JNAL, Quesada PM, Spoor CW. Kinematic evaluation of the finger’s interphalangeal joints coupling mechanism-variability, flexion-extension differences, triggers, locking swanneck deformities, anthropometric correlations. J Biomech 2010;43:2381–93. https://doi.org/10.1016/j.jbiomech.2010.04.021. [161] Šenk M, Chèze L. Rotation sequence as an important factor in shoulder kinematics. Clin Biomech 2006;21:3–8. https://doi.org/10.1016/j.clinbiomech.2005.09.007. [162] Small CF, Bryant JT, Pichora DR. Rationalization of kinematic descriptors for three- dimensional hand and finger motion. J Biomed Eng 1992;14:133–41. https://doi.org/10.1016/0141-5425(92)90018-G. [163] Dabirrahmani D, Hogg M. Modification of the Grood and Suntay Joint Coordinate System equations for knee joint flexion. Med Eng Phys 2017. https://doi.org/10.1016/j.medengphy.2016.10.006. [164] Razavian RS, Greenberg S, McPhee J. Biomechanics imaging and analysis. Encycl Biomed Eng 2019;1–3:488–500. https://doi.org/10.1016/B978-0-12-801238-3.99961-6. 120 [165] Gates DH, Walters LS, Cowley J, Wilken JM, Resnik L. Range of motion requirements for upper-limb activities of daily living. Am J Occup Ther 2016;70. https://doi.org/10.5014/ajot.2016.015487. [166] Wu G, Van Der Helm FCT, Veeger HEJ, Makhsous M, Van Roy P, Anglin C, et al. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion - Part II: Shoulder, elbow, wrist and hand. J Biomech 2005;38:981–92. https://doi.org/10.1016/j.jbiomech.2004.05.042. [167] Arthritis Foundation. Arthritis by the Numbers: Book of Trusted Facts & Figures 2020. Arthritis Found 2020:98. [168] Özkan B, Keskin D, Bodur H, Barça N. The effect of radiological hand osteoarthritis on hand function. Clin Rheumatol 2007;26:1621–5. https://doi.org/10.1007/s10067-007- 0555-8. [169] Haugen IK, Englund M, Aliabadi P, Niu J, Clancy M, Kvien TK, et al. Prevalence, incidence and progression of hand osteoarthritis in the general population: The Framingham Osteoarthritis Study. Ann Rheum Dis 2011;70:1581–6. https://doi.org/10.1136/ard.2011.150078. [170] Felson DT. Epidemiology of hip and knee osteoartrritis. Epidemiol Rev 1988;10:1–28. https://doi.org/10.1093/oxfordjournals.epirev.a036019. [171] Felson DT. NIH Conference Osteoarthritis : New Insights. Ann Intern Med 2000;133:637–9. [172] Damen A, Van der Lei B, Robinson PH. Carpometacarpal arthritis of the thumb. J Hand Surg Am 1996. https://doi.org/10.1016/S0363-5023(96)80196-1. [173] Kaufman KR, An KN, Litchy WJ, Cooney WP, Chao EYS. In-vivo function of the thumb muscles. Clin Biomech 1999. https://doi.org/10.1016/S0268-0033(98)00058-8. [174] Glickel SZ. Clinical assessment of the thumb trapeziometacarpal joint. Hand Clin 2001. https://doi.org/10.1016/s0749-0712(21)00239-0. [175] Carr MM, Freiberg A. Osteoarthritis of the thumb: Clinical aspects and management. Am Fam Physician 1994. [176] Makhsous M, Lin F, Cichowski A, Cheng I, Fasanati C, Grant T, et al. Use of MRI images to measure tissue thickness over the ischial tuberosity at different hip flexion. Clin Anat 2011. https://doi.org/10.1002/ca.21119. [177] Su FC, Kuo LC, Chiu HY, Chen-Sea MJ. Video-computer quantitative evaluation of thumb function using workspace of the thumb. J Biomech 2003;36:937–42. 121 https://doi.org/10.1016/S0021-9290(03)00073-3. [178] Kennedy CA, Beaton DE, Smith P, Van Eerd D, Tang K, Inrig T, et al. Measurement properties of the QuickDASH (Disabilities of the Arm, Shoulder and Hand) outcome measure and crosscultural adaptations of the QuickDASH: A systematic review. Qual Life Res 2013;22:2509–47. https://doi.org/10.1007/s11136-013-0362-4. [179] Wewers ME, Lowe NK. A critical review of visual analogue scales in the measurement of clinical phenomena. Res Nurs Health 1990;13:227–36. https://doi.org/10.1002/nur.4770130405. [180] Macdermid JC, Fox E, Richards RS, Roth JH. Validity of pulp-to-palm distance as a measure of finger flexion. J Hand Surg Am 2001;26 B:432–5. https://doi.org/10.1054/jhsb.2001.0612. [181] Van Heest AE, Kallemeier P. Thumb carpal metacarpal arthritis. J Am Acad Orthop Surg 2008. https://doi.org/10.5435/00124635-200803000-00005. [182] Su FC, Lin CJ, Wang CK, Chen GP, Sun YN, Chuang AK, et al. In vivo analysis of trapeziometacarpal joint arthrokinematics during multi-directional thumb motions. Clin Biomech 2014. https://doi.org/10.1016/j.clinbiomech.2014.08.012. [183] Marshall M, Watt FE, Vincent TL, Dziedzic K. Hand osteoarthritis: clinical phenotypes, molecular mechanisms and disease management. Nat Rev Rheumatol n.d. https://doi.org/10.1038/s41584-018-0095-4. [184] Freedman DM, Eaton RG, Glickel SZ. Long-term results of volar ligament reconstruction for symptomatic basal joint laxity. J Hand Surg Am 2000;25:297–304. https://doi.org/10.1053/jhsu.2000.jhsu25a0297. [185] Eaton RG, Lane LB, Littler JW, Keyser JJ. Ligament reconstruction for the painful thumb carpometacarpal joint: A long-term assessment. J Hand Surg Am 1984;9:692–9. https://doi.org/10.1016/S0363-5023(84)80015-5. [186] Wolf JM, Schreier S, Tomsick S, Williams A, Petersen B. Radiographic Laxity of the Trapeziometacarpal Joint Is Correlated With Generalized Joint Hypermobility. J Hand Surg Am 2011;36:1165–9. https://doi.org/10.1016/J.JHSA.2011.03.017. [187] Hart DJ, Spector TD. Definition and epidemiology of osteoarthritis of the hand: A review. Osteoarthr Cartil 2000;8:2–7. https://doi.org/10.1053/joca.2000.0326. [188] Arden N, Nevitt MC. Osteoarthritis: Epidemiology. Best Pract Res Clin Rheumatol 2006;20:3–25. https://doi.org/10.1016/j.berh.2005.09.007. [189] Herrero-Beaumont G, Roman-Blas JA, Castañeda S, Jimenez SA. Primary Osteoarthritis No Longer Primary: Three Subsets with Distinct Etiological, Clinical, and Therapeutic 122 Characteristics. Semin Arthritis Rheum 2009;39:71–80. https://doi.org/10.1016/J.SEMARTHRIT.2009.03.006. [190] Lawrence JS, Bremner JM, Bier F. Osteo-arthrosis. Prevalence in the population and relationship between symptoms and x-ray changes. Ann Rheum Dis 1966;25:1–24. https://doi.org/10.1136/ard.25.1.1. [191] Pellegrini VD. Osteoarthritis at the base of the thumb. Orthop Clin North Am 1992;23:83– 102. https://doi.org/10.1016/s0030-5898(20)31717-x. [192] Yuan F, Aliu O, Chung KC, Mahmoudi E. Evidence-Based Practice in the Surgical Treatment of Thumb Carpometacarpal Joint Arthritis. J Hand Surg Am 2017;42:104- 112.e1. https://doi.org/10.1016/j.jhsa.2016.11.029. [193] Yin Q, Berkhout MJL, Ritt MJPF. Current trends in operative treatment of carpometacarpal osteoarthritis: a survey of European hand surgeons. Eur J Plast Surg 2019;42:365–8. https://doi.org/10.1007/s00238-019-01528-8. [194] Pellegrini VD, Burton RI. Surgical management of basal joint arthritis of the thumb. Part I. Long-term results of silicone implant arthroplasty. J Hand Surg Am 1986. https://doi.org/10.1016/S0363-5023(86)80136-8. [195] Ambike, Satyajit, Paclet, Florent, Latash, Mark, Zatsiorsky V. Grip‑force modulation in multi‑finger prehension during wrist_Ambike.pdf. Exp Brain Res 2013:509–22. [196] O’Driscoll SW, Horii E, Ness R, Cahalan TD, Richards RR, An KN. The relationship between wrist position, grasp size, and grip strength. J Hand Surg Am 1992;17:169–77. https://doi.org/10.1016/0363-5023(92)90136-D. [197] Richards LG, Olson B, Palmiter-Thomas P. How Forearm Position Affects Grip Strength. Am J Occup Ther 1996;50:133–8. https://doi.org/10.5014/ajot.50.2.133. [198] Härkönen R, Piirtomaa M, Alaranta H. Grip strength and hand position of the dynamometer in 204 finnish adults. J Hand Surg Am 1993;18:129–32. https://doi.org/10.1016/0266-7681(93)90212-X. [199] Seo NJ, Armstrong TJ, Ashton-Miller J, Chaffin D. Wrist strength is dependent on simultaneous power grip intensity. Ergonomics 2008;51:1594–605. https://doi.org/10.1080/00140130802216925. [200] Marley RI, Wehrman RR. Grip strength as a function of forearm rotation and elbow posture. Proc. Hum. Factors Soc., 1992. https://doi.org/10.1177/154193129203601033. [201] Li ZM. The influence of wrist position on individual finger forces during forceful grip. J Hand Surg Am 2002. https://doi.org/10.1053/jhsu.2002.35078. 123 [202] Fitzhugh FE. Grip strength performance in dynamic gripping tasks. Occup Saf Heal Eng 1973:39–40. [203] Pryce JC. The wrist position between neutral and ulnar deviation that facilitates the maximum power grip strength. J Biomech 1980. https://doi.org/10.1016/0021- 9290(80)90343-7. [204] Kraft GH, Detels PE. Position of function of the wrist. Arch Phys Med Rehabil 1972. [205] Lee SC, Wu LC, Chiang SL, Lu LH, Chen CY, Lin CH, et al. Validating the Capability for Measuring Age-Related Changes in Grip-Force Strength Using a Digital Hand-Held Dynamometer in Healthy Young and Elderly Adults. Biomed Res Int 2020;2020:1–9. https://doi.org/10.1155/2020/6936879. [206] Kroemer KH, Gienapp EM. Hand-held device to measure finger (thumb) strength. J Appl Physiol 1970;29:526–7. https://doi.org/10.1152/jappl.1970.29.4.526. [207] Vocelle AR, Shafer G, Bush TR. Determining Isolated Thumb Forces in Osteoarthritic and Healthy Persons. J Biomech Eng 2021;143. https://doi.org/10.1115/1.4048712. [208] Dominick KL, Jordan JM, Renner JB, Kraus VB. Relationship of radiographic and clinical variables to pinch and grip strength among individuals with osteoarthritis. Arthritis Rheum 2005;52:1424–30. https://doi.org/10.1002/art.21035. [209] Wolfe T, Chu JY, Woods T, Lubahn JD. A systematic review of postoperative hand therapy management of basal joint arthritis. Clin Orthop Relat Res 2014;472:1190–7. https://doi.org/10.1007/s11999-013-3285-z. [210] Cooney WP, An KN, Daube JR, Askew LJ. Electromyographic analysis of the thumb: A study of isometric forces in pinch and grasp. J Hand Surg Am 1985;10:202–10. https://doi.org/10.1016/S0363-5023(85)80106-4. [211] Bourbonnais, Daniel, Duval P. Static dynamometer for the measurement of multidirectional forces exerted by the thumb. Med Biol Eng Comput 1991;29:413–8. [212] Carpometacarpal joint. Orthop Artic n.d. https://www.orthopaedicsone.com/x/ygPbB (accessed June 21, 2023). [213] Vergara M, Sancho-Bru JL, Gracia-Ibáñez V, Pérez-González A. An introductory study of common grasps used by adults during performance of activities of daily living. J Hand Ther 2014;27:225–34. https://doi.org/10.1016/j.jht.2014.04.002. [214] Yorke AM, Curtis AB, Shoemaker M, Vangsnes E. Grip strength values stratified by age, gender, and chronic disease status in adults aged 50 years and older. J Geriatr Phys Ther 2015;38:115–21. https://doi.org/10.1519/JPT.0000000000000037. 124 [215] Janssen I, Heymsfield SB, Wang ZM, Ross R. Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr. J Appl Physiol 2000;89:81–8. https://doi.org/10.1152/jappl.2000.89.1.81. [216] Abe T, Kearns CF, Fukunaga T. Sex differences in whole body skeletal muscle mass measured by magnetic resonance imaging and its distribution in young Japanese adults. Br J Sports Med 2003;37:436–40. https://doi.org/10.1136/bjsm.37.5.436. [217] Kim J, Wang ZM, Heymsfield SB, Baumgartner RN, Gallagher D. Total-body skeletal muscle mass: Estimation by a new dual-energy X-ray absorptiometry method. Am J Clin Nutr 2002;76:378–83. https://doi.org/10.1093/ajcn/76.2.378. [218] Detailed Occupation by Sex Education Age Earnings: ACS 2019 n.d. https://www.census.gov/data/tables/2022/demo/acs-2019.html. [219] Hauraix H, Goislard De Monsabert B, Herbaut A, Berton E, Vigouroux L. Force-Length Relationship Modeling of Wrist and Finger Flexor Muscles. Med Sci Sports Exerc 2018;50:2311–21. https://doi.org/10.1249/MSS.0000000000001690. [220] Delp SL, Grierson AE, Buchanan TS. Maximum isometric moments generated by the wrist muscles in flexion-extension and radial-ulnar deviation. J Biomech 1996. https://doi.org/10.1016/0021-9290(96)00029-2. [221] Nordin M, Frankel VH. Basic biomechanics of the musculoskeletal system. 2012. https://doi.org/10.1136/bjsm.26.1.69-a. [222] Lehmkuhl L, Smith L. Brunnstrom’s Clinical Kinesiology. 4th ed. Philadelphia: 1983. [223] Woody R, Mathiowetz V. Effect of forearm position on pinch strength measurements. J Hand Ther 1988;1:124–6. https://doi.org/10.1016/S0894-1130(88)80037-1. [224] Norkin D. C& W. Measurement of Joint Motion: A Guide to Goniometry, Fifth Edition. 2016. [225] Lieber RL, Loren GJ, Friden J. In vivo measurement of human wrist extensor muscle sarcomere length changes. J Neurophysiol 1994;71:874–81. https://doi.org/10.1152/jn.1994.71.3.874. [226] Loren GJ, Shoemaker SD, Burkholder TJ, Jacobson MD, Fridén J, Lieber RL. Human wrist motors: Biomechanical design and application to tendon transfers. J Biomech 1996. https://doi.org/10.1016/0021-9290(95)00055-0. [227] An KN, Chao EY, Cooney WP, Linscheid RL. Normative model of human hand for biomechanical analysis. J Biomech 1979;12:775–88. https://doi.org/10.1016/0021- 9290(79)90163-5. 125 [228] Winter DA. Biomechanics and Motor Control of Human Movement: Fourth Edition. 2009. https://doi.org/10.1002/9780470549148. [229] Burton RI, Pellegrini VD. Surgical management of basal Joint arthritis of the thumb. Part II. Ligament reconstruction with tendon interposition arthroplast. J Hand Surg Am 1986. https://doi.org/10.1016/S0363-5023(86)80137-X. [230] Soejima O, Hanamura T, Kikuta T, Iida H, Naito M. Suspensionplasty with the abductor pollicis longus tendon for osteoarthritis in the carpometacarpal joint of the thumb. J Hand Surg Am 2006;31:425–8. https://doi.org/10.1016/j.jhsa.2005.12.010. 126