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This is to certify that the
thesis entitled

AN ANALYSIS OF PRESSURE DISTRIBUTION WITH A
PREFABRICATED FOOT ORTHOTIC ON A SYMPTOMATIC
POPULATION

presented by

William J. Vascik

has been accepted towards fulfillment
of the requirements for the

MS. degree in Kinesiolm

 

 

/ Major Professor’s Signature

07/3//a6

Date

 

MSU is an Afl’umative Action/Equal Opportunity Institution

 

 

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PLACE IN RETURN BOX to remove this checkout from your record.
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DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2/05 p:lC|RC/Date0ue.indd~p.1

 

AN ANALYSIS OF PRESSURE DISTRIBUTION WITH A
PREFABRICATED FOOT ORTHOTIC ON A SYMPTOMATIC
POPULATION

BY

William J. Vascik

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTERS OF SCIENCE IN KINESIOLOGY

College of Education

2006

 

ABSTRACT

AN ANALYSIS OF PRESSURE DISTRIBUTION WITH A PREFABRICATED
FOOT ORTHOTIC ON A SYMPTOMATIC POPULATION

BY
William J, Vascik

The purpose of this study was to study the effect of a
locally manufactured prefabricated foot orthotic on the
role of force distribution through the plantar forefoot.
It is theorized that an equal distribution of plantar
pressures is desired, to reduce the incidence of forefoot
overuse injuries. Plantar pressures were analyzed with an
in-shoe device called the Parotec—System. Plantar pressure
distribution was calculated by averaging plantar pressures
and calculating a lateral:medial ratio. Results indicated
that plantar pressures were significantly reduced in the
lateral forefoot, as well as a significant medial deviation
in plantar pressure ratios, with use of the orthotic. It
was concluded that although pressure deviated medially in
the midfoot, it should not be seen as a negative outcome.
This was due to a significant reduction in lateral
pressures due to the high arch support in the orthotic.
Additionally, the orthotic appears to be an effective tool‘
in reducing lateral forefoot pressures, potentially
reducing the incidence of fifth metatarsal stress

fractures.

ACKNOWLEDGEMENTS

First and foremost, I would like to thank my mother,
Kathy, father Art, Grandma Louise, and brothers Kevin and
Scotty. Everybody has given me more support than I could
have ever asked for throughout my years in school and life.
I thank you for stressing the importance of growing up with
a level head, being respected in the community, and
receiving a proper education. You will never know how much
that means to me.

To the people who I met as classmates in 2004 when I
moved to Michigan, whom I now call my family. I've truly
enjoyed the past 2 years here. I especially have to
acknowledge my roommates Kyle & Leigh which represented “G”
the way it should have.

To Dr. John Powell, Dr. Tracey Covassin, and Dr. Roger
Haut, who believed in me throughout this study and helped
me grow as a clinician in sports medicine. To Adam,
Jerrod, and Pam, who assisted with many aspects of the
study. You guys helped me keep the little sanity I have
left. Lastly, to Curt Munson & the Playmakers staff, your
support and hospitality during testing was incredible. I
could have not asked for the assistance that was given to

me by the entire staff.

TABLE OF CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF TABLES- Vi
LIST OF FIGURES viii
CHAPTER 1
INTRODUCTION 1
CHAPTER 2
LITERATURE REVIEW .4
Anatomy & Physiology 4
Gait Mechanics 11
Foot Mechanics 91
Plantar Pressures 14
Orthotics 25
CHAPTER 3
METHODS 53
Objective 83
Research Design 53
Subjects S4
Instrumentation q5
Testing Procedures 58
Data Analysis 51
CHAPTER 4
ANALYSIS OF RESULTS 64
Statistical Analysis 57
CHAPTER 5
DISCUSSION 75
Analysis Of Plantar Pressure Data 75
Analysis of Pressure Ratios in Control
and Experimental Conditions 80
Analysis Among Genders 81
Analysis Among Age Groups 83
Clinical Implications 84
Sources of Measurement Error 85
Considerations for the Future 86
Limitations to the Study 89
Conclusions 90
APPENDIX A
PARTICIPANT MEAN PRESSURE DATA 9l

 

APPENDIX B
PARTICIPANT MEAN RATIO DATA

94

 

APPENDIX C

 

UCRIHS APPROVAL FORM

APPENDIX D
HUMAN SUBJECTS CONSENT FORM

96

98

 

APPENDIX E

 

PARTICIPANTS DEMOGRAPHICS FORM

BIBLIOGRAPHY

 

102

105

LIST OF TABLES

TABLE 4.1

 

Participant Demographic Information _

TABLE 4.2
Participant Characteristic Informationm

 

TABLE 4.3
Descriptive Statistics for Plantar Pressure
Means Without and With Stabil Lite Orthotic in
Medial Forefootlu.v '

 

TABLE 4.4
Individual 2x2 Repeated Measures ANOVAS
Comparing Medial Forefoot Without and With Use
of Stabil Lite Orthotic

 

TABLE 4.5
Descriptive Statistics for Plantar Pressures
Means Without and With Stabil Lite Orthotic in
Lateral Forefoot

 

TABLE 4.6
Individual 2x2 Repeated Measures ANOVAS Comparing
Lateral Forefoot Without and With Use of Stabil
Lite Orthotic

 

TABLE 4.7
Descriptive Statistics for Plantar Pressure

Ratio Means Between R/L Foot

 

TABLE 4.8
Individual 2x2 Repeated Measures ANOVAS
Comparing Right and Left Foot With Use of
Stabil Lite Orthotic"- -

 

TABLE 4.9
Descriptive Statistics for Plantar Pressure

Ratio Means Between Gender-

 

TABLE 4.10
Individual 2x2x2 Repeated Measures ANOVAS
Comparing Mean Pressure Ratios Without/With

Orthotic and Gender

65

W66

68

68

"69

-69

"70

W70

72

”72

TABLE 4.11
Descriptive Statistics for Plantar Pressure
Ratio Means Between Age Groups , "-74

 

TABLE 4.8
Individual 2x2x2 Repeated Measures ANOVAS
Comparing Mean Pressure Ratios Without/With
Orthotic and Age ' -“74

vii

LIST OF FIGURES

 

 

 

 

 

 

 

FIGURE 2.1

Pronation and supination of the foot
FIGURE 2.2

Initial contact in gait mechanics .....
FIGURE 2.3

Loading response in gait mechanicsl"
FIGURE 2.4

Midstance in gait mechanics
FIGURE 2.5

Terminal stance in gait mechanics .H--
FIGURE 2.6

Preswing in gait mechanics“
FIGURE 2.7

Navicular drop non—weightbearing and

weightbearing
FIGURE 2.8

Superior view of Stabil Lite for right foot

FIGURE 2.9

Anterior View of Stabil Lite for right foot-

FIGURE 2.10
Medial view of Stabil Lite for right foot

 

 

 

FIGURE 2.11

 

Lateral view of Stabil Lite for right footm

FIGURE 3.1
A schematic of the Parotec—System insole

 

FIGURE 3.2
The Parotec-System insole

 

FIGURE 3.3
The Parotec—System wiring stabilized to the

shank

fl“

12

15

"16

18

.19

-.21

-.26

51

”51

-62

m52

56

56

”57

FIGURE 3.4
The Parotec-System computer stabilized to the
Torso

 

FIGURE 3.5

 

Parotec-System insole numbering

FIGURE 5.1
Met-head rocker sole--

 

k

57

64

78

Chapter 1: Introduction

Optimal function of the body depends on the ability to
maintain proper biomechanics through static and dynamic
motions. These structures must be capable of adapting to a
variety of internal and external influences to function
properly. If there is a disturbance in the body’s natural
function, performance may be affected, leading to injury.

A variety of factors may affect the body’s ability to
maintain proper mechanics to achieve optimal performance.
For example, improper mechanics may create abnormal
pressure across the plantar surface of the foot. If a
small area of the foot absorbs repetitive, abnormal
pressure, then that area may be susceptible to developing
minor injuries, such as blisters or corns. More severe
injuries include stress fractures and lesions in diabetic
patients. It is theorized that an equal distribution in
forefoot plantar pressure is desired to limit forefoot
overuse injury.

Due to the extensive number of structures, proper
mechanics and function of the foot may be more critical for
optimal performance than any other structure in the lower
extremity. When mechanics are not synchronous, techniques
may be used to “fix” the problem, such as orthotic

intervention. Today, foot orthotics are being prescribed

very frequently for lower-extremity ailments. Often,
custom-molded orthotics are tailored to each patient to
correct structural abnormalities in the lower extremity.
Although pain relief often comes with introduction of the
device, outcomes are unpredictable. Numerous studies have
shown both positive outcomes and neutral outcomes from
custom orthotic intervention (Bratta, 2004; Denegar &
Miller, 2002; Ekenman, Milgrom, Finestone, Begin, Olin,
Arndt & Burr, 2002; Fish, 1998; Franco, 1987; Gross, Davlin
& Evanski, 1991; Guskiewicz & Perrin, 1996; Hertel,
Denegar, Monroe & Stokes, 1999; Hertel & Olmsted, 2004;
Hertel, Sloss & Earl, 2005; Hockenbury, 1999; Janisse,
1998; Kupperman, 2005; Mattacola, 2005; Mattacola & Dwyer,
2002; Mundermann, Nigg, Humble & Stefanyshyn, 2003; Nigg
Nurse & Stefanyshyn, 1999; Nigg, Stergiou, Cole,
Stefanyshyn, Mundermann & Humble, 2003; Ochsendorf,
Mattacola & Arnold, 2000; Williams, McClay—Davis & Baitch,
2003). Unfortunately, relief comes with a hefty price tag
when purchasing custom orthotics.

One potential alternative to expensive, custom-molded
orthotics is using generic, prefabricated orthotics.
Numerous shapes, sizes, and brands are available to
customers in pharmacies, grocery stores, and shoe stores.

Sometimes, clinicians will suggest using a prefabricated

orthotic prior to prescribing a custom-molded orthotic. If
the patient’s problem has not subsided, it may warrant
using a custom-molded device. Surprisingly, little
clinical research has been conducted on the effectiveness
of prefabricated orthotics. This is perplexing due to the
wide assortment of prefabricated orthotics on the market
and the plethora of ailments they are designed to
alleviate.

One such device, the Stabil Lite, is frequently used
to alleviate foot pain. It is produced by Playmakers
(East, Lansing, MI). Many testimonials have praised its
effectiveness in the reduction of foot pain resulting from
plantar fasciitis, metatarsal stress fractures, and
hyperpronation. Because this device is used frequently in
sports medicine in the Mid—Michigan area, it is
advantageous to analyze why it is clinically effective.

This study examined the effectiveness of the Stabil
Lites in creating uniform plantar pressures across the
forefoot. It is theorized that the Stabil Lite is
clinically effective in injury management because of its
ability to offset or redistribute plantar pressures equally

in the forefoot.

Chapter 2: Literature Review

Anatomy & Physiology

 

The ankle and foot are complex segments in the body,
due to the number of bones (26) and joints (over 30
synovial joints) and neurological anatomy that can control
motion (Yuk San Tsung, Zhang, Fan & Boone, 2003). These
structures must work together to achieve optimal
performance. If the structures are abnormal or injured,
altered gait may result.

The “true ankle joint”, or talocrural joint, is made
up of the distal portions of the tibia and fibula and the
superior surface of the talus- It is responsible for ankle
plantar flexion and dorsiflexion. The subtalar joint is
comprised of the inferior surface of the talus and the
superior aspect of the calcaneous. The subtalar joint is
responsible for ankle inversion and eversion (Arnheim &
Prentice, 1999). These joints work together to control the
ankle in coordinated movements.

The foot is divided into two distinct areas based on
function and mechanics. Twenty—one bones make up the
forefoot’s structure. These bones are the 5 metatarsals,
14 phalanges, and 2 sesamoids. The rearfoot is comprised
of the talus and calcaneous. The navicular, cuboid, and

three cuneiforms make up the midfoot. These areas of the

body can exhibit a variety of malalignments, which will be
discussed further in the “Foot Mechanics” section in this
chapter.

The medial longitudinal arch is a very important
structure for proper biomechanics of the lower extremity.
The medial longitudinal arch is found in the medial aspect
of the foot and spans from the anterior surface of the
calcaneous to the head of the first metatarsal. In
podiatry, the medial longitudinal arch height is measured
to classify foot type. Foot type classification according
to the medial longitudinal arch will be covered in detail
in the “Foot Mechanics” section of this chapter-

At a standing-at-ease posture, very little muscle
activity occurs to maintain the arch height. Instead,
static structures, such as the plantar fascia, plantar
ligaments, and spring ligament maintain the arch's height
(Kaufman, Brodine, Shaffer, Johnson & Cullison 1999;
Wearing, Smeathers, Yates, Sullivan, Urry, & DuBois, 2004).
During dynamic movements, the medial longitudinal arch acts
to store elastic strain energy and react as elastic recoil
(Kaufman, et al., 1999). The medial longitudinal arch is
also responsible for dissipating forces during weight
bearing prior to reaching the long bones of the leg and

thigh (Franco, 1987). Dynamic movements in the medial

longitudinal arch are also aided by the posterior tibialis
muscle (Kaufman, et al., 1999; Kulig, Burnfield, Requenjo,
Sperry & Terk, 2004; Wearing, et al., 2004).

The muscles of the lower extremity are very complex
and aid in both static and dynamic stability, while also
creating coordinated movements. Three muscles are oriented
laterally for concentric ankle eversion and resist ankle
inversion and moments in the lateral direction. These are
the peroneus longus, peroneus brevis, and peroneus tertius.
The peroneus longus muscle acts as the primary defense
mechanism against an inversion perturbation targeted at the
ankle (Cordova, Cardona, Ingersoll & Sandrey, 2000).

Medially, the posterior tibialis muscle acts to
concentrically invert the ankle and resist eversion and
moments in the medial direction. The posterior tibialis is
also important to aid in shock absorption (Kulig, et al.,
2004) and maintain dynamic arch height. Chronic weakening
of this muscle can lead to development of acquired adult
flatfoot deformity (Kitaoka, Kura, Luo & An, 2000; Kitaoka
& Patzer, 1997; Kulig, et al., 2004).

Two muscles are found anteriorly to concentrically
dorsiflex the ankle and resist ankle plantar flexion and
deviations in the anterior direction. These muscles are

the tibialis anterior and extensor digitorum longus (Krell,

Cinelli & Patla, 1998). The extensor digitorum longus also
concentrically extends the phalanges.

Posteriorly, the gastrocnemius and the soleus act as
the main propulsive force in gait by concentrically plantar
flexing the foot, while resisting forces from the posterior
direction during standing. The flexor digitorum, also
oriented posteriorly, acts to plantar flex the foot and
flex the phalanges. These muscles collectively act
together to resist deviations in the posterior direction
(Krell, et al., 1998; Schepsis, Jones & Haas, 2002).
Activation of all the lower extremity muscles (particularly
in the A/P direction) maintains stability- This is called
the ankle strategy (Krell, et al., 1998).

Central and peripheral components of the central
nervous system constantly process information to influence
the maintenance of the postural-control system (PCS).
Peripheral components include somatosensory, visual, and
vestibular systems (Cote, Brunet, Gansneder & Shultz, 2005;
Riemann, 2002; Riemann & Lephart, Part I, 2002; Willems,
Witvrouw, Verstuyft, Vaes & De Clerq, 2002). The central
nervous system processes stimuli from these systems and
adjusts muscle tension around the affected joint to
maintain homeostasis. The phenomenon with the PCS is that

even when one peripheral component is restricted (example,

shutting the eyes), stability typically is not compensated
(Riemann, 2002).

The postural—control system must function properly for
optimum balance. Balance is defined as the process of
maintaining the center of gravity within the body’s base of
support (Cote, et al., 2005). Any joint can alter balance
in the lower extremity, due to the fact that the foot is
fixed in the closed kinetic chain. One component of
balancing is postural stability. Riemann and Lephart (Part
I, 2002) define stability as “state of a joint remaining or
promptly returning to proper alignment through an
equalization of forces”. It has also been defined as a
function requiring the coordinated activation of joint,
muscle, visual, and vestibular receptors to maintain the
body's center of mass (Harkins, Mattacola, Uhl, Malone &
McCrory, 2005).

Postural stability is influenced by homeostasis of the
body. Homeostasis is constantly regulated in the body by
two processes: feedback controls and feedforward controls.
Feedback (reactive) controls are initiated following a
sensory detection and correct the organism following the
perturbation (Riemann, 2002; Riemann & Lephart, Part I,
2002). This constant processing by the body is regulated

by afferent information (Riemann, 2002; Riemann & Lephart,

 

Part I, 2002). Feedforward (preparatory) controls are
actions initiated by the body to maintain homeostasis when
anticipating a disruption (Riemann, 2002; Riemann &
Lephart, Part I, 2002). Unlike feedback control,
feedforward controls are inactive until feedback controls
are initiated (Riemann & Lephart, Part I, 2002).

As previously stated, postural stability is important
because it keeps the structures in the lower extremity in
prOper alignment. When the body is in proper alignment,
plantar pressures should equally be distributed across the
foot to prevent overuse injuries. When postural stability
is compromised, the foot may be susceptible to increased
pressures at specific anatomic landmarks in the forefoot.
This may predispose individuals to injuries at that site.

Postural stability depends on the body having optimal
stability over the center of pressure and optimal activity
from mechanoreceptors (Harkins, et al., 2005).
Mechanoreceptors are joint afferents within ligaments,
muscles, and cutaneous tissue that are mostly influenced by
gamma motor neurons (Hertel, Buckley & Denegar, 2001;
Riemann & Lephart, Part II, 2002; Riemann, Myers, &
Lephart, 2002). Specifically, these mechanoreceptors are

responsible for a sense called proprioception. It is

defined as the conscious awareness of limb movement and
position (Pincivero & Coelho, 2001).

Proprioception is enhanced by visual and auditory
signals (Riemann, Myers, & Lephart, 2002). The
mechanoreceptors that act predominantly on proprioception
are Ruffini-type receptors, Pacinian corpuscles, and Golgi
tendon organ receptors (Riemann & Lephart, Part I, 2002).
These structures are maintained by spinal level reflexes
(Pincivero & Coelho, 2001). These specialized structures
are important to maintain a proprioceptive role in ankle
joint dynamic stability and coordinated motor patterns.
Additionally, stimulation of these mechanoreceptors affects
sensitivity and activation of gamma motor neurons in the
muscle spindles in the surrounding musculature (Myers,
Riemann, Hwang, Fu & Lephart, 2003).

Specifically, cutaneous afferent mechanoreceptors in
the glabrous skin of the foot, Merkel cell complexes under
the epidermis, Meissner corpuscles in the superficial
epidermis, and Pacinian corpuscles in deep dermal layers
all work in conjunction to provide sensory input from a
variety of force thresholds in the plantar aspect of the
foot, which arise from gamma motor neurons (Nigg, et al.,
1999, Riemann &Lephart, Part II, 2002). These cutaneous

afferents have been shown to be very important in the role

10

of maintaining postural stability and joint stability, due
to an increase in the gamma motor neuron activation, which
is a theory why orthotics are effective (Gribble, Hertel,
Denegar & Buckley, 2004; Mattacola, 2005; Riemann &
Lephart, Part II, 2002).

Gait.Mechanics

 

Gait mechanics vary from individual to individual.
The smallest abnormality in any part of the biomechanical
chain can greatly alter proper gait mechanics. Although
gait may appear to vary from individual to individual,
general patterns and phases exist in average adults.

Independent motions occur in both the rearfoot and
forefoot. Rearfoot motions that occur are plantar
flexion/dorsiflexion (sagittal-plane motions),
inversion/eversion (frontal-plane motions), and
internal/external rotation or abduction/adduction
(transverse-plane motions). A natural combination of these
motions allows for movement about an axis of rotation
oblique to the long axis of the lower leg called pronation
and supination (Hertel, 2002). While the foot is in
contact with the ground, also called the closed kinetic
chain, pronation is the combination of eversion, external
rotation/abduction of the foot, and plantar flexion of the

talus (Hertel, 2002). Normal range of motion of pronation

11

 

has been listed at 4-8° (Neely, 1998). In the closed
kinetic chain, supination is the combination inversion,
dorsiflexion of the talus, and internal rotation/adduction
(Hertel, 2002). Figure 2.1 displays pronation and

supination of the foot around the foot axis.

 
   
    

Pronation

Supmanon

Figgge 2.1. Pronation and supination of the foot around the
foot axis (Bratta, 2004)

Research has found that females demonstrate a higher
degree of pronation compared to males (Zeller, McCrory &
Uhl, 2003). Using EMG and kinematic analysis, Zeller and
colleagues (2003) found an inability to maintain a knee
varus position in a single-legged squat. The increase in
valgus angle results in hyperpronation (Zeller, et al.,
2003). Anatomically, females should demonstrate a higher
degree of pronation compared to males. Generally, females

tend to have a wider pelvis. This creates a greater knee

12

 

valgus angle, which results in increases in rearfoot
pronation.

There are two forms of gait terminology: the
Traditional terminology and the Rancho Los Amigos (RLA)
terminology. The Rancho Los Amigos terminology will be
used throughout this study. The RLA method is divided in
the stance phase and swing phase. The stance phase
(closed—kinetic chain) occurs when the initial contact of
the heel is on the ground and ends as the toe leaves the
ground. It is further divided into initial contact,
loading response, midstance, terminal stance, and preswing.

The swing phase (open—kinetic chain) occurs between
toe-off and the next contact by the heel (Starkey & Ryan,
2002). The stance phase is of interest, due to the
research being concentrated on ground reaction forces.
Figures 2.2-2.6 depict the position of the leg in the
closed-kinetic chain, while also displaying the movement of
the center of pressure during gait (Starkey & Ryan, 2002).
It should be noted that the center of pressure locations in
the figures are seen in a pes rectus (anatomically correct)
foot. Structural abnormalities of the foot will alter the

' ' ' \\
center of pressure position and 18 discussed in the Foot

Mechanics” section.

13

Normal gait mechanics begin at initial contact. The
subtalar joint is supinated prior to initial contact.
Typically, the joint everts quickly 4°-5° at initial contact
by the lateral aspect of the plantar surface of the heel
(Manoli, 2001; Neely, 1998; Starkey & Ryan, 2002). This
allows for a maximal amount of energy to be absorbed at
heel strike. Energy absorption is possible due to
pronation unlocking the structures of the.midtarsal joints
and metatarsals (Franco, 1987; Neely, 1998; Starkey & Ryan,
2002). The subtalar joint unlocking also aids in
maintaining balance, improving efficiency of muscle
contraction and assist in distribution of forces through
the lower kinetic chain (Neely, 1998).

During this period, both feet are in contact with the
ground at the same time. This period represents
approximately 20% of the total gait cycle (Starkey & Ryan,
2002). Figure 2.2 depicts where the leg is positioned and

where the center of pressure is located during initial

contact .

14

Initial Contact

 

5.1-.“

l? L-'.-‘
. __.\ r_..,,

”—5..-ng-

Figgre 2.2. Initial contact in gait mechanics (Starkey &
Ryan, 2002)

The next phase in the RLA terminology is the loading
response. As the foot transfers to the loading response,
the body’s weight and center of pressure is transferred to
the supple lateral border of the foot (Manoli, 2001;
Starkey & Ryan, 2002). The foot flattening due to the
unlocking of the midtarsal joints and metatarsals allows

the foot further absorbs energy from the initial contact

phase (Franco, 1987; Starkey & Ryan, 2002). Additionally,

the tibialis posterior eccentrically contracts, which

attempts to decelerate the rate of pronation (Starkey &

15

 

 

Ryan, 2002). Figure 2.3 depicts where the leg is
positioned and where the center of pressure is located
during the loading response. Note the center of pressure

moving anteriorly along the lateral border of the foot.

Loading Response

 

Figgre 2.3. Loading response in gait mechanics (Starkey &
Ryan, 2002)

Midstance is defined as the period when the body
weight moves directly over the support limb and concludes

when the center of gravity is directly over the foot

(Starkey & Ryan, 2002). The forefoot and rearfoot is seen

being evenly distributed on the ground (Starkey & Ryan,

16

2002). As the talocrural joint initiates dorsiflexion, the
subtalar joint begins to supinate, resulting in calcaneal
inversion (Franco, 1987; Starkey & Ryan, 2002).
Approximately 10° of supination will lock the midtarsal
joints, which makes the foot more rigid (Franco, 1987;
Konradsen, 2002; Starkey & Ryan, 2002). This is
advantageous, so the foot can prepare to act as a lever
during propulsion at toe-off (Franco, 1987; Neely, 1998;
Starkey & Ryan, 2002).

Beginning in this phase, the posterior shank
musculature contracts to prevent the anterior movement of
the tibia over the planted foot (Schepsis, Jones & Haas,
2002). Figure 2.4 depicts where the leg is positioned and
where the center of pressure is located during midstance.
Note the center of pressure moving anteromedial towards the

first ray as the foot prepares for toe-off.

17

Midstance

 

Figgre 2.4.2Midetance in gait mechanics (Starkey & Ryan,
2002)

As the foot prepares for terminal stance, the center
of gravity passes over the foot and ends before the
contralateral foot strikes the ground (Starkey & Ryan,
2002). The center of gravity begins to transfer to the
forefoot, where the metatarsal heads and sesamoids of the
first metatarsal equally distribute the weight (Manoli,
2001; Starkey & Ryan, 2002).

The posterior shank musculature continues to contract
to prevent anterior movement of the tibia over the planted

foot (Schepsis, Jones & Haas, 2002). Lastly, the posterior

18

tibialis lock the transverse tarsal joints, which aids in
creating a rigid foot for propulsion (Kulig, et al., 2004).
Figure 2.5 depicts where the leg is positioned and where
the center of pressure is located during terminal stance.
Note the center of pressure moving to the head of the first

metatarsal as the foot prepares for toe-off.

Terminal Stance

 

Figgre 2.5.‘Termina1 stance in gait.mechanics (Starkey &
Ryan, 2002)

Preswing is the final period in the stance phase.
This is a transitional period of double support and ending

in toe-off. In this phase the ankle is maximally

dorsiflexed, then the ankle quickly plantar flexes to 20°-

19

30° at toe-off (Mullin, 2003; Starkey & Ryan, 2002).
Further supination occurs in the subtalar joint and the
transverse tarsal joint becomes locked prior to toe-off
(Franco, 1987; Hockenbury, 1999). This is where most of
the forefoot’s stresses occur, which can lead to overuse
injuries (Hockenbury, 1999).

Finally, the first metatarsal ends ground contact at
toe—off to heel lift and the subtalar joint is positioned
at approximately 4° of inversion (Franco, 1987; Mullin,
2003; Starkey & Ryan, 2002). The triceps surae complex
contracts concentrically to initiate propulsion (Schepsis,
Jones & Haas, 2002). The phalanges reach maximum
dorsiflexion, especially the first phalange. This places
strain on the plantar fascia, which aids in elevating the
medial longitudinal arch. This is termed the windlass
mechanism (Franco, 1987; Hockenbury, 1999). Figure 2.6
depicts where the leg is positioned and where the center of
pressure is located during pre-swing. Note the center of
pressure is at the distal portion of the first metatarsal

at toe-off.

20

Preswf . 1an

 

 

Figgre 2.6. Preswing in gait mechanics (Starkey 8 Ryan,
2002)

Fbot.Mechanics

Foot mechanics, size, shape, and mobility vary in all
individuals. Because of the variety of feet a clinician
will encounter in a given day, analyzing structural
abnormalities can be a difficult task.

The foot tends to reshape during weightbearing
conditions compared to non-weightbearing conditions. Yuk
San Tsung and colleagues (2003) found using a 3—dimensional

analysis machine, foot length will increase up to 3.4% and

21

foot width will increase up to 6.0 % under weight-bearing
conditions. Additionally, weightbearing conditions

typically demonstrate a decrease in arch height, which is
why it is necessary to analyze foot mechanics dynamically.

Because the foot's ground contact is relatively small
in area, the tiniest amount of skeletal malalignment in the
foot and ankle complex can alter the body’s biomechanics.
Skeletal malalignments can be defined as abnormal joint
alignment or a deformity within a particular bone (Riegger-
Krugh & Keysor, 1996). Skeletal malalignments can alter
the joint's load distribution, adjacent or distal joint's
contact pressure distribution, excessive joint contact
pressures, inability of joints to shock absorb properly, or
reduced joint surface contact areas (Riegger—Krugh &
Keysor, 1996). This can result in abnormal plantar
pressures being seen across the foot and can result in
injury.

A number of structural abnormalities throughout the
foot are indicators for foot types. Abnormalities occur
both in the forefoot and rearfoot. Forefoot deformities
are more common due to more bones potentially creating more
problems (Bratta, 2004). Deformities in the forefoot are
categorized as either forefoot varus or forefoot valgus and

are analyzed by looking at the alignment of the metatarsal

22

heads. Forefoot varus is defined as an inward tipping
(inversion) of the forefoot on the rearfoot with the
subtalar joint in neutral (Neely, 1998). Forefoot varus is
clinically the most common intrinsic deformity seen in the
lower extremity (Neely, 1998). Compensation for a forefoot
varus deformity often includes eversion of the subtalar
joint, hyperpronation, and a hypermobile forefoot (Neely,
1998). Forefoot valgus is defined as having an outward
tipping (eversion) of the forefoot on the rearfoot with the
subtalar joint in neutral. Because this abnormality is
fairly uncommon and has many causes of its occurance
(Michaud, 1997), little research is devoted to study it
further.

Similar names are given in the rearfoot, termed
rearfoot valgus and rearfoot varus. Rearfoot deformities
are analyzed by the alignment of the calcaneous and
Achilles tendon. Rearfoot valgus is more common than
rearfoot varus and is defined when there is excessive
subtalar valgum and the subtalar joint rotates medially
(Bratta, 2004). Conversely, rearfoot varus is defined as
excessive subtalar varum, which allows the subtalar joint
to rotate laterally (Bratta, 2004).

Numerous methods have been developed to evaluate and

classify the foot at the subtalar joint, rearfoot, and

23

forefoot. The main tool to assess foot alignment is
through a theoretical position called subtalar neutral,
developed by Merton Root, DPM. This position is when all
the bones in the subtalar joint and talocrural joint line
up equally in the open packed positions. This position is
important because optimal foot alignment theoretically
occurs in the subtalar neutral position. The clinician
finds this position by having the patient lie prone on an
exam table with their opposite hip flexed, abducted and
externally rotated. The examiner uses the hand of the
contralateral side of the foot being tested to feel the
motion of the anterior talus and the ipsilateral hand moves
the foot in inversion and eversion. The clinician feels
for an equal protrusion of the talus on the medial and
lateral sides. Once subtalar neutral is found, custom
orthotics can be created to maintain subtalar neutral
during gait (Mullin, 2003).

Research sited by Groner (2005) has since found that
Root’s work may be partially incorrect. In their study,
only 17% of the 58 subjects they analyzed had “normal” foot
alignment according to Root’s standards and definitions.
This error by Root was concluded to be the result of a
misinterpretation of earlier work in podiatry.

Additionally, Song and colleagues (1996) state that there

24

is low intertester reliability seen when finding subtalar
neutral. Although some clinicians discount Root's work, it
still is the primary assessment tool in foot alignment
evaluation.

Measuring the arch height is often used to classify
foot types and analyze motions of the foot. A variety of
methods have been developed to do this. One method is
measuring the arch height by navicular drop. This is done
by the most prominent part of the navicular being marked,
then having the affected foot placed in subtalar neutral.
A card is placed next to the navicular and the position of
the navicular from the ground is marked on the card. The
patient is then instructed to stand in a relaxed position
and the new position of the navicular is marked on the
card. Excessive pronation is classified as the distance
between the marks on the card exceeding 7 mm (Mullin,
2003).

Other authors have suggested that individuals with a
navicular drop less than 5 mm as being supinators, 5—10 mm
being neutral, and greater than 10 mm as being pronators
(Bratta, 2004; Hargrave, Carcia, Gansneder & Shultz, 2003;
Neely, 1998). Figure 2.7 shows a schematic of how the

navicular drops inferiorly when the foot is weightbearing.

25

 

Figgre 2.7. Navicular drop non-weightbearing (A) and
weightbearing (B) (Bratta, 2004)

Arch height can also be measured using calipers.
Neely (1998) suggests this measurement to be the most
reliable versus calculation by footprint parameters.
Average arch heights are said to fall between 2.12 i 0.67
mm and 2.83 i 0.44 mm.

A more technical method has been developed to measure
arch height. This calculation is called the arch index.
This calculates a ratio of the area of the middle third of
the footprint to the entire footprint area. The developers
of this method classify a high arch as an arch index <
0.21, a normal arch as 0.21 < arch index < 0.26, and a flat
arch as arch index 2 0.26 (Cavanaugh & Rodgers, 1987).

The bony arch index is an alternative method to

classify arch height. This is calculated as the ratio of

26

navicular height to foot length (Kaufman, et al., 1999;
Wen, Puffer & Schmalzried, 1997) or truncated foot length
(posterior calcaneous to the first metatarsophalangeal
joint) (Bratta, 2004; Kulig, et al., 2004). Although these
are good numerical methods of classifying the arches,
factors such as height, body weight, subcutaneous fat, and
soft tissue motion can provide false calculations by
clinicians (Hargrave, et al., 2003).

Recently, three-dimensional analysis of foot structure
through computed tomography has been suggested (Edwards,
2004). Researchers at the Rehabilitation Research and
Deve10pment Center of Excellence for Limb Loss Prevention
and Prosthetic Engineering at the VA Puget Sound (WA) and
the departments of orthopedics, sports medicine, and
mechanical engineering at the University of Washington in
Seattle developed a computer program, which classify foot
types using Euler angles. This process was developed due
to structural differences in feet being three-dimensional-
A strong correlation was found with this computer program
by verification of foot classification types versus
orthopedic surgeons in their classification of foot type
(Edwards, 2004).

Typically, there are three general shapes to feet,

determined by the medial longitudinal arch and rearfoot and

27

forefoot positioning. The classifications are pes cavus,
or arched feet, pes planus, or flat feet, and pes rectus,
or “anatomically correct” feet. It has been noted that
individuals with feet regarded as either pes cavus or pes
planus have an increased incidence of overuse injuries
compared to individuals with average arch height (Kaufman,
et al., 1999; Korpelainen, Orava, Karpakka, Siira & Hulkko,
2001; Neely, 1998; Seligman, 2004).

Pes cavus feet typically are associated with
excessively high arches, a hypersupinated foot, and
hypomobile midfoot (Cote, et al., 2005; Kaufman, et al.,
1999). “Flexible” pes cavus feet do exist, but they are
not as prominent as rigid pes cavus feet (Franco, 1987).
Additional anatomic signs that are related to pes cavus are
rearfoot varus, forefoot valgus, and a plantar flexed first
metatarsal (Hertel, Sloss & Earl, 2005; Manoli, 2001).

Feet classified as pes cavus tend to distribute pressures
abnormally over the metatarsal heads and lateral border of
the foot (Franco, 1987).

Gait mechanics are altered due to the pes cavus
malalignment. The heel typically strikes in supinated
position, causing the center of pressure of the foot to be
medial to the subtalar joint axis (Olmsted—Kramer & Hertel,

2004). Because rearfoot eversion is limited, shock—

28

 

absorbing capacity is decreased in the subtalar joint
(Bratta, 2004; Neely, 1998; Song, Hillstrom, Secord &
Levitt, 1996). During mid—stance, the lateral border of
the foot, which is typically supple, is fairly rigid. This
is due to the increase height of the medial longitudinal
arch. As the weight of the body is transferred to the
forefoot, the plantar flexed first metatarsal strikes the
ground first, which tips the entire foot in an everted
position (Manoli, 2001). The supinated position of the
subtalar joint also reduces propulsion efficiency in the
pre-swing phase (Song, et al., 1996).

The abnormal pressure distribution due to the high
arch can cause a variety of overuse injuries, such as
callus formation/contusions under the first and fifth
metatarsal heads (Franco, 1987), sesmoiditis (Manoli,
2001), and stress fractures to the metatarsals (Franco,
1987; Kaufman, et al., 1999; Manoli, 2001; Neely, 1998;
Omey & Micheli, 1999; Weist, Eils & Rosenbaum, 2004).
Other injuries that are common with pes cavus feet are
inversion ankle sprains (Manoli, 2001; Neely, 1998;
Olmsted—Kramer & Hertel, 2004; Song, et al., 1996),
peroneal tendonosis/subluxations (Bratta, 2004; Manoli,
2001; Neely, 1998), Achilles tendon tendonitis and ruptures

(Neely, 1998; Schepsis, Jones, Haas, 2002), Jones fractures

29

(Manoli, 2001), stress fractures to the tibia (Franco,

1987; Kaufman, et al., 1999; Manoli, 2001; Neely, 1998;
Omey & Micheli, 1999), plantar fasciitis (Manoli, 2001;
Neely, 1998; Wearing, et al., 2004), and varus joint strain
to the knee (Manoli, 2001).

The converse to a pes cavus foot is a pes planus foot.
This structural abnormality is characterized by excessively
flat arches caused by a medially displaced talus. Other
signs associated with pes planus are a pronated foot,
rearfoot valgus, inverted forefoot, and hypermobile
midfoot, resulting in the structural abnormality being
termed “flexible flatfoot” (Chen, Chen, Lew, Hsieh, Yang &
Tang, 2003; Franco, 1987; Hertel, Sloss & Earl, 2005;
Kitaoka & Patzer, 1997). This condition has been reported
to occur in 15% of the general population (Omey & Micheli,
1999).

Another characteristic of pes planus feet is the “too—
many—toes” sign, which was described in the 1980’s by Ken
A. Johnson, MD. The “too—many—toes” sign can be seen from
a posterior view of the weightbearing foot. The clinician
will see excessive heel valgus and more toes laterally due
to an abducted forefoot (Manoli, 2001).

Pes planus is often developed over one’s lifespan as a

result of weakness in the posterior tibialis. This is

30

 

termed posterior tibial tendon dysfunction and results in
acquired flatfoot deformity in adults (Kitaoka & Patzer,
1997; Kitaoka, et al., 2000; Kulig, et al., 2004).

Acquired adult flatfoot deformity can also result from weak
flexor digitorum longus and flexor hallucis longus muscles,
diabetes mellitus, obesity, and hypertension (Kitaoka &
Patzer, 1997). Pronation can result from compensation of
another structural deformity from soft tissues, osseous
deformities, limitations of muscular flexibility, leg
length discrepancies, forefoot varus, subtalar varus, lack
of ankle dorsiflexion, femoral neck anteversion, tibial
torsion, or tibial/genu varum (Neely, 1998).

Like the pes cavus foot, foot mechanics are greatly
altered in the pes planus foot. Due to the medial
longitudinal arch being flatter, an angle greater than 90°
between the rearfoot and forefoot is created. Static
equilibrium then is not achieved, due to the center of mass
and ground reaction force not counteracting each other. If
an imbalance exists with the tensile strain of the passive
plantar mechanism, the soft tissues in the sole will
deform, causing plantar hypermobility and instability.

With a decrease in the medial longitudinal arch
height, the head and neck of the talus will plantar flex,

adduct, and internally rotate abnormally. Forefoot varus

31

and pes planus will increase due to the calcaneous becoming
abnormally everted, abducted, and dorsiflexed. As a
result, over—pronation and tibial internal rotation will
occur during gait. Over time, the peroneus brevis will
assume a mechanical advantage over the posterior tibialis,
resulting in an even more drastic pronation action during
toe-off (Maurer, 2003). With all this motion occurring in
the foot, ligamentous structures become weakened due to the
foot relying on them for stability. This decreases
stability, resulting in the foot relying on intrinsic and
extrinsic musculature, specifically the anterior and
posterior tibialis to aid in stability (Franco, 1987;
Neely, 1998).

Overpronation is typically seen with a pes planus
deformity. The amount of pronation can be fairly severe
(reported as high as 10-12° (Neely, 1998)), causing a
plethora of issues in the biomechanical chain. Some
suggest that a mild degree of pronation may be protective
against lower extremity injuries (Neely, 1998). Hreljac
(2004) notes that the majority of clinical studies
conducted find that injured runners tended to exhibit
hyperpronation. Abnormal plantar pressures resulting from
hyperpronation deformities can predispose individuals to

metatarsal stress fractures (Franco, 1987; Kitaoka &

32

Patzer, 1997; Neely, 1998). Other overuse injuries
associated with hyperpronation include medial tibial stress
syndrome (Franco, 1987; Hreljac, 2004; Neely, 1998),
plantar fasciitis (Bratta, 2004; Seligman, 2004; Song, et
al., 1996; Wearing, et al., 2004), heel spur development as
a result of chronic plantar fasciitis (Song, et al., 1996),
patellofemoral syndrome (Franco, 1987), anterior cruciate
ligament injuries (Hargrave, et al., 2003), tibialis
posterior tendon and Achilles tendon tendonitis (Bratta,
2004; Omey & Micheli, 1999), and Achilles tendon ruptures
(Schepsis, Jones & Haas, 2002). As severe as the injuries
that may develop with a pes planus abnormality, the
majority of these individuals experience no pain or
discomfort (Omey & Micheli, 1999).

Although the base of support is greater with pes
planus malalignments, muscle activity is altered at the
ankle, knee, and hip, which may compromise balancing
capabilities (Cote, et al., 2005). This may be due to an
overload of plantar sensory information, which the body
cannot process thoroughly. Regardless of the structural
malalignments, joint mechanics are altered significantly

during dynamic activities.

33

Plantar Pressures

 

During gait, plantar pressures are seen as being the
highest in the heel during heel strike and under the
metatarsal heads during toe-off. This can be very
problematic for diabetic patients. It has been
demonstrated that sensations on the plantar surface of feet
in diabetics become reduced compared to healthy feet. As
demonstrated by Nurse and Nigg (2001), when normal feet had
an acute loss of sensation, plantar pressures increased at
the metatarsal heads and decreased pressures around the
periphery. Thus, it should not be surprising that
diabetics frequently have problems with ulceration at the
metatarsal heads (Blackwell, et al., 2002; Nurse & Nigg,
2001).

Excessive plantar pressures are also detrimental to
athletes in developing stress fractures in the metatarsals.
It has been suggested that increased pressures in the feet
increase risk for developing stress fractures, especially
in the second and third metatarsals (Boden, Osbahr &
Jiminez, 2001; Eils, Streyl, Linnenbecker, Thorwesten,
Volker & Rosenbaum, 2004; Gross & Bunch, 1989; Weist, et
al., 2004). It has been reported that metatarsal stress
fractures make up between 9—18% of all reported stress

fractures (Boden, et al., 2001, Gross & Bunch, 1989). The

34

second metatarsal is most prone to developing stress
fractures due to it being more firmly secured at the base
than other metatarsals, thereby transmitting more force
through the bone (Boden, et al., 2001).

A study conducted by Eils and colleagues (2004)
utilizing an in-sole pressure measuring device, peak
pressures were greatest in the heel and metatarsal heads
(first and second ray) for running and in the forefoot
(especially the medial forefoot) during soccer—specific
movements. It is not surprising that the majority of
stress fractures in the foot occur along the second
metatarsal, approximately where the greatest peak pressures
were located during movements. Similarly, Weist and
colleagues (2004) found significant increases in the peak
pressures under the second and third metatarsal heads
during a fatiguing protocol on a treadmill. Additionally,
Gross and Bunch (1989) estimated using biomechanical models
and force transducers that the second and first metatarsal
heads experienced the highest forces and were as high as
340 N and 280 N, respectively, during a running protocol.

Orthotics

 

Kitaoka, Luo, and An (1997) estimate that between six
and ten million individuals use custom orthotics for a

variety of problems. The “success rates” of custom

35

orthotics in studies have ranged from 50% to 90% (Hunter,
1997; Mundermann, et al., 2003; Nigg, et al., 1999).
Satisfaction of the orthotic will depend on factors, such
as foot shape, skeletal alignment, joint motion, foot
sensitivity, forces acting on the musculoskeletal system,
and muscle activity (Mundermann, et al., 2003).

A questionnaire developed by Gross and colleagues
(1991) analyzed the use of inserts for symptomatic relief
of lower extremity complaints in long—distance runners.
Among the 347 participants, 31.1% used an insert for
excessive pronation, 13.5% used an insert for a leg length
discrepancy, 12.6% used an insert for patellofemoral
disorders, 20.7% used an insert for plantar fasciitis,
18.5% used an insert for Achilles tendonitis, 7.2% used an
insert for shin splints, and 4.9% used an insert for
miscellaneous reasons. Over 75% of the respondents
reported complete resolution or great improvements of their
symptoms. A high degree of satisfaction was seen because
90% of the runners continued to wear the insert even after
resolution of their symptoms.

Orthotics are classified as prefabricated or custom-
molded models and vary in stiffness. Stiffness levels are
classified as flexible, semi-rigid, or rigid (Hertel &

Olmsted, 2004). The more rigid an orthotic is, the more

36

control and support can be influenced in motion (Hertel &
Olmsted, 2004; Janisse, 1998; Seligman, 2004). Conversely,
the more flexible the orthotic is, the less motion can be
controlled while offering more shock absorption and
cushioning (Hertel & Olmsted, 2004; Janisse, 1998;

Seligman, 2004). Often, a semirigid orthotic is used,

which offer more cushioning than a rigid orthotic, but more
support than a soft orthotic (Janisse, 1998). This is
often preferred in athletics where pivoting is involved
(Franco, 1987). A post is a wedge added into an orthotic
to decrease a particular motion or “bring the ground up to
the foot” (Franco, 1987). In hyperpronation, medial wedges
may be utilized (Janisse, 1998; Seligman, 2004). A lateral
wedge may be utilized for ankle instabilities or varus heel
deformity (Janisse, 1998).

Currently, the literature is filled with studies
looking at the benefits of custom-molded orthotics.
Clinicians primarily prescribe orthotics to prevent
developing an overuse injury or to avoid a common movement—
related injury (Gross, et al., 1991; Mundermann, et al.,
2003; Nigg, et al., 1999; Nigg, et al., 2003; Williams, et
al., 2003) and to properly align the skeleton due to
structural abnormalities (notably in the lower extremity)

(Bratta, 2004; Denegar & Miller, 2002; Fish, 1998; Gross,

37

et al., 1991; Hertel, et al., 1999; Hertel & Olmsted, 2004;
Hockenbury, 1999; Janisse, 1998; Mattacola, 2005; Mattacola
& Dwyer, 2002; Nigg, et al., 1999; Nigg, et al., 2003;
Williams, et al., 2003). Other reasons orthotics are used
are to provide additional impact cushioning (Bratta, 2004;
Ekenman, et al., 2002; Hertel & Olmsted, 2004; Janisse,
1998; Kupperman, 2005; Nigg, et al., 1999), reduce stress
fractures (Ekenman, et al., 2002; Hertel, et al., 1999),
improve sensory feedback (Kupperman, 2005; Mattacola, 2005;
Nigg, et al., 1999; Nigg, et al., 2003; Ochsendorf, et al.,
2000), alter neuromuscular control (Franco, 1987;
Guskiewicz & Perrin, 1996; Hertel & Olmsted, 2004; Hertel,
Sloss & Earl, 2005; Kupperman, 2005), improve healing
following a lateral ankle sprain (Denegar & Miller, 2002;
Guskiewicz & Perrin, 1996; Hertel & Olmsted, 2004;
Mattacola, 2005; Mattacola & Dwyer, 2002; Ochsendorf, et
al., 2000), reduce stabilizing muscle activity (Kupperman,
2005; Hertel & Olmsted, 2004; Nigg, et al., 2003),
improving balance in healthy and unhealthy ankles (Denegar
& Miller, 2002; Mattacola, 2005; Mattacola & Dwyer, 2002;
Nigg, et al., 2003; Ochsendorf, et al., 2000), improve
performance (Mundermann, et al., 2003), and improve comfort

(Ekenman, et al., 2002; Hertel & Olmsted, 2004; Hockenbury,

38

1999; Janisse, 1998; Mundermann, et al., 2003; Nigg, et
al., 1999; Nigg, et al., 2003).

So why do orthotics work? Traditional thinking has
focused on a reduction in deviation and velocity of motion
of the foot and proximal segments of the lower extremity,
especially in the clinical population (Kupperman, 2005;
Nigg, et al., 2003). This is due to a reduction in
rearfoot pronation or supination and tibial rotation and a
decrease in knee abduction and adduction movements (Hertel
& Olmsted, 2004; Williams, et al., 2003). Hertel and
Olmstead (2004) use the example with a forefoot varus foot.
To control this motion, a medial post is placed at the
metatarsal heads. This is in attempt to provide a block
and reduce excessive forefoot pronation and reduce strain
on the posterior tibialis and soleus muscle origins on the
posterior aspect of the tibial shaft.

Additionally, orthotics may properly align the
skeleton, notably in the subtalar joint. Structural
malalignments predispose individuals to a variety of
problems. Ottaviani, Ashton-Miller, and Wojtys (2001)
quote, “mosteological risk factors...are thought to include
excessive talar tilt”. A variety of studies cited by Nigg

and colleagues (1999) reported a reduction in rearfoot

eversion position between 1-3° with the introduction of

39

orthotics and reduction in tibial internal rotation by 2°.
If talar tilt is maintained in a neutral position and
unnecessary muscle strain is reduced, then these orthopedic
injuries may be lessened.

In a study by Ochsendorf and colleagues (2000), the
authors concluded that center of pressure deviations were
reduced in individuals wearing custom orthotics due to the
cradle effect. The first part of the cradle effect says
that the talocrural joint alignment will be improved and
the ankle mortise will be in more of a neutral position.
This results in neuromuscular alterations that will be
discussed shortly.

The theory of the skeletal realignment has been
challenged recently, due to research showing little
variations in individual responses to orthotic
intervention. In a study by Wen and colleagues (1997) and
prospective study by Nigg and colleagues (1999) analyzing
lower extremity alignment and risk of overuse injuries in
marathon runners, both studies concluded that lower
extremity alignment was not considered a major predisposing
factor or predictor for overuse running injuries. Another
study by Nigg and colleagues (2003) hypothesized that in

the normal, healthy population, the skeleton cannot be

40

realigned. This is due to the skeletal movement being
“preprogrammed”, thus not being able to alter mechanics.

Chen and colleagues (2003) also state that the
literature is limited for support of orthotics to correct
flexible flatfoot abnormalities. Factors that compound the
problem of flexible flatfoot are the need for a precise
correction of forefoot pronation, which is difficult to do
with a goniometer and clinicians thinking that only a
medial longitudinal arch support is suffice to correct the
problem.

The new theory on why orthotics work is due to
alterations in neurological information processing.
Examples are increases in plantar cutaneous receptor
activation, changing the afferent input, and neuromuscular
activation from the somatosensory system (Hertel & Olmsted,
2004; Ochsendorf, et al., 2000). Kupperman (2005) cites a
few studies in which orthotic intervention resulted in
increased muscle EMG intensities, notably in the peroneus
longus, hamstrings, and tibialis anterior. Hertel, Sloss
and Earl (2005) reported an increase in vastus medialis and
gluteus medius EMG levels with the use of prefabricated
orthotics in patients with all three foot-type
classifications (pes planus, pes cavus, and pes rectus)

during dynamic motions. This increase in muscle activity

41

can possibly reduce tibial rotation, which in turn may
reduce hyperpronation, dampen soft tissue vibration in the
lower extremities, or increase activity in the hip strategy
to maintain postural control.

Another theory behind the effectiveness of orthotics
is the increased comfort of individual’s feet. How can
comfort be described physiologically when this is a fairly
subjective concept? As pointed out by Nigg and colleagues
(1999), comfort can be related to dynamic stability. A
comfortable orthotic will have a direct relationship with
reducing muscle tension and theoretically, equally
distribute plantar pressures due to altering a
biomechanical abnormality. If the individual is
uncomfortable with their feet due to a biomechanical
abnormality, increased plantar pressures should be evident
in certain areas of the foot. Also, a reduction in muscle
activity would stabilize joints and minimize soft tissue
vibration (Nigg, et al., 1999).

A few articles have been devoted to the effect of
orthotics on plantar pressures. Results have found
reduction in plantar pressures (Cobb, Limroongreungrat, Tis
& Higbie, 2003; Hacker, Walsh, Bokser, Grogers, Walden &
Walsh, 2005; Higbie, Tis, Lichty, Dupont & McCarty, 1998;

Hodgson, Tis & Cobb, 2005) and conversely studies have

42

found increases in plantar pressures (Donahue, Higbie,
Simpson & Wisenbaker, 1996; Willis, McCurdie, Jones & Bain,
2005), especially in the medial forefoot. According to the
authors, the reasoning for increases in plantar pressures
can be attributed to the stiffness of the material
comprising the orthotic.

As previously mentioned, literature is very limited
analyzing the use of prefabricated orthotics on foot
pathology. Researchers appear to be analyzing their
effectiveness more extensively. There are three reasons
that prefabricated orthotics should be used. First, they
possibly can prevent overuse injury. Second, they help to
determine if a patient's pathology is mechanically related,
or from another source. Third, they provide temporary
relief while a custom orthotic is made (Groner, 2005).
There are two types of prefabricated orthotics:
accommodative and functional. Accommodative prefabricated
orthotics are shaped to offload a particular area of the
foot and used mostly for patients with arthritis and
diabetes. Functional prefabricated orthotics alters the
foot’s mechanics in attempt to correct some malalignments
(Groner, 2005).

Typically, prefabricated orthotics are designed for a

variety of foot variations, but Arthur Manoli, MD has

43

developed a prefabricated orthotic that is designed
specifically for pes cavus feet called the “cavus foot
orthosis” (CFO). The CFO is constructed of
ethylvinylacetate that is heated to be custom molded to the
foot. Fitting of the orthotic is done by arch height, not
foot length. Many features make this insert specific for
the cavus foot. First, the elevated heel cushion increase
shock absorption and aid with the tight triceps surae
complex. Second, an intrinsic lateral heel wedge induces
inversion and redistributes pressures to a larger area of
the foot. The arch support is generally less pronounced
than a generic prefabricated orthotic. This, combined with
a recess under the first metatarsal allows for some
rearfoot pronation, by aiding in the plantar flexed first
ray. Lastly, a forefoot wedge is incorporated laterally to
the first metatarsal ray to accommodate the forefoot valgus
(Manoli, 2001).

Only three articles have been found that analyzed the
effectiveness of prefabricated orthotics directly on the
foot or ankle. The first study was conducted by Finestone,
Novack, Farfel, Berg, Amir and Milgrom (2004). They
compared a prefabricated orthotic versus custom—molded
orthotics that were soft or semi-rigid, in the incidence of

stress fractures, ankle sprains, foot problems, and comfort

levels in a military population. The authors conducted a
single-blinded clinical trial among 874 Israeli infantry
recruits during basic training. The authors introduced
either custom or prefabricated soft or semi—rigid orthotics
to the recruits for 14 weeks during basic training. Every
three weeks, the recruits were screened for foot problems
by orthopedists. Results indicated that there was no
significant difference documented in incidence of stress
fractures, ankle sprains, or foot problems using all types
of orthotics. Additionally, it was discovered that the
recruits who wore the “soft custom” orthotics wore the
devices significantly fewer times than the soft
prefabricated orthotics. As a result, the authors suggest
that there is no reason to prescribe expensive, semirigid
orthotics when similar preventative measures can be made by
a simple, inexpensive prefabricated orthotic.

The second study relating to prefabricated orthotics
was performed by Kitaoka and colleagues (1997). In their
study, they analyzed arch support efficacy using two
commonly prescribed prefabricated orthotic devices on 14
fresh cadaveric feet and shanks. Using a loading frame,
axial loads of 222, 445, or 667 Newtons were applied while
a magnetic tracking system performed three-dimensional

analysis on the talus, calcaneous, navicular, and first

45

metatarsal. They found that the arch supports had an
immediate effect on foot alignment throughout a variety of
axial loads versus axial loads without the orthotics. It
was observed that foot alignment had been maintained
because the arch supports had effectively increased the
arch heights.

The last study on prefabricated orthotics was
conducted by Landorf, Keenan, and Herbert (2004). It was a
thorough evidence-based review on different types of foot
orthotics for the treatment of plantar fasciitis. They
concluded throughout all the studies they analyzed, both
custom—molded and prefabricated orthotics offer benefits to
reduce pain stemming from plantar fasciitis. Due to the
problems seen in random control trials, one device cannot
be seen as being more beneficial than the other.

Only one study has been found in the literature which
stated that prefabricated orthotics were inferior to custom
orthotics. Using a F-Scan in—shoe pressure system, Hacker,
et al., (2005) concluded that plantar pressures in the
forefoot and heel were reduced by a significant amount with
the use of a custom orthotic versus a prefabricated
orthotic. The authors did not analyze the reduction of
plantar pressures of the custom or prefabricated orthotics

compared to baseline readings, so it is unknown what role

46

the prefabricated orthotics have against a baseline
reading. Additionally, the analysis was on a normal adult
population, so it is unsure what the results would be on an
injured or malaligned population.

Research is beginning to show that prefabricated
orthotics may also have benefits in the knees and hips.
Two studies showed that prefabricated orthotics might be
useful in treating osteoarthritis of the knee (Groner,
2005). Additionally, research is being shown that
prefabricated orthotics may increase muscle activity
further up the biomechanical chain. In a study by Hertel,
Sloss, and Earl (2005), EMG levels in the vastus medialis
and gluteus medius muscles during squat and step—down
exercises, regardless of the posting that was introduced to
the orthotic or the subject’s foot type, were higher than
under the control conditions. It was theorized that
prefabricated orthotics showed beneficial results due to
the increased cutaneous activation in the plantar aspect of
the foot, rather than altering the position of the joints
of the feet.

The general consensus in the studies is that
prefabricated orthotics can have a positive effect on
symptomatic patient’s feet or show no difference in

performance versus custom orthotics, despite their generic

47

design. Like custom-molded orthotics, prefabricated
orthotics can possibly offer benefits in injury reduction
and pain maintenance.

Orthotics may alter plantar pressures via three
processes: alteration in neuromuscular activation, proper
alignment of the skeleton, and an increase in plantar
cutaneous sensory activity. Research has shown evidence
that an increase in muscle activity is achieved with the
introduction of an orthotic in the hips and thigh (Hertel,
Sloss & Earl, 2005). This increase in muscular activation
distally allows for a decrease in muscle activation in the
foot, since these muscles now do not have to strain
themselves to keep the structures stable in the foot. This
decrease in muscle tension in the foot can be advantageous
in physically active individuals. If the foot’s
musculature is constantly active to keep the structures
stable, fatigue is inherent. As Boden and colleagues
(2001) state, muscular fatigue at intrinsic muscles in the
feet may predispose individuals to excessively high plantar
pressures, leading to metatarsal stress fractures. If the
orthotic can reduce some muscular activation, then fatigue
can be staved off for a longer period of time, reducing the

chance of developing a stress fracture.

48

Secondly, the proper alignment of the skeleton results
in a more stable joint structure. The orthotic may create
the body’s preferred alignment, resulting in an increase in
joint stability. If the joint structure is more stable,
then the subtalar joint should not deviate in great
distances from subtalar neutral (Cote, et al., 2004; Fish,
1998; Denegar & Miller, 2002; Gross, et al., 1991; Hertel,
et al., 1999; Hertel & Olmsted, 2004; Hockenbury, 1999;
Janisse, 1998; Mattacola, 2005, Mattacola & Dwyer, 2002;
Nigg et al., 1999; Nigg, et al., 2003; Williams, et al.,
2003). This should again result in an equal pressure
distribution across the foot.

Lastly, it has been hypothesized that having an
increase in cutaneous sensation allows the body to be more
aware of its proprioception, resulting in a more stable
base of support (Kupperman, 2005; Mattacola, 2005; Nigg, et
al., 1999; Nigg, et al., 2003; Ochsendorf, et al., 2000)
and have more control in gait patterns (Nurse & Nigg,
2001). In a study by Hertel, Gay, and Denegar (2002),
individuals who had a pes cavus deformity had a significant
reduction in postural stability compared to individuals
with pes rectus or pes planus feet. To test the effective
of orthotics on these individuals, Hertel and Olmsted

(2004) found that orthotic intervention improved dynamic

49

stability in individuals with pes cavus feet. They
attributed this to an increase in mechanical support,
leading to enhanced sensory receptor activity and
neuromuscular function. Nurse and Nigg (2001) also
demonstrated that when a reduction in plantar sensation was
initiated by ice, the participants tended to increase their
plantar pressures at areas that had a normal sensation.
These studies demonstrate that increased and equal plantar
pressures are advantageous to individuals.

The intervention that will be introduced to the groups
are Stabil Lite insoles, manufactured by Playmakers (East
Lansing, MI). This device is manufactured from closed—cell
foam molded from a pes rectus foot. It has a high arch for
support and deep heel cup to control rear-foot motion.
Figures 2.8-2.11 shows different views of the % length

Stabil Lites for a right foot.

50

 

 

  

Fiflre 2.9. Anterior view of Stabil Lite for right foot

51

 

 

 

 

  

Fiflre 2.11. Lateral view of Stabil Lite for right foot

52

Chqgter 3: Methods

Objective

 

The objective of this study was to determine the role
of the Stabil Lite orthotics on plantar pressure
distribution at the forefoot during a dynamic protocol on a
“clinical population”. Research has demonstrated
equivalent results in multiple studies using prefabricated
orthotics versus custom-molded orthotics. This equivalency
has not been studied in pressure distribution. It is
hypothesized that plantar pressure distribution will be
more evenly distributed in the forefoot with the
introduction of the Stabil Lite orthotics versus baseline
control measurements. As previously mentioned, a foot with
minimal structural abnormalities will demonstrate equal
plantar pressures across the metatarsal heads. The Stabil
Lite should either 1) support the foot’s natural mechanics,
creating equal pressure across the forefoot or 2) increase
plantar cutaneous mechanoreceptor activation, which would
encourage optimal biomechanics of the forefoot.

Research Design

 

The set—up of this study was an A—B counterbalanced
design. The dependent variable was the Stabil Lite

orthotic intervention. The independent variable was the

53

plantar pressure distribution across the forefoot measured
with the Parotec—System.
Subjects

This study consisted of 20 subjects (10 female, 10
male), who voluntarily participated at the testing site.
The tests were conducted at a local athletic shoe store,
which has a free, weekly injury clinic. Because each
subject acted as their own control, there were 20
participants in the control group and 20 participants in
the experimental group.

At this clinic, local physicians, physical therapists,
and massage therapists offer free evaluations of orthopedic
injuries. Often, the clinicians suggest purchasing an
orthotic to alleviate the patient's ailment. If an insert
was suggested, then the individual was asked if they would
be interested in participating in the study.

Inclusion criteria were: 1) between the ages of 18 and
35 years old, 2) no previous lower extremity orthopedic
surgery, 3) no uncorrectable visual or balancing problems,
and 4) had not used an orthotic device or insert for the
past six months. The participants were of varying heights,

weights, shoe sizes, pain location, and activity level.

54

Ins trumen ta ti on

 

To conduct this study, a mobile pressure device,
called the Parotec-System (Paromed Medizintechnik GmbH,
Neubeuern, Germany) was used. This portable pressure
insole system has 24 pressureemeasuring sensors, called
hydrocells, which slip into any shoe under the plantar
aspect of the foot. There are corresponding insoles to fit
a variety of shoe sizes, according to European
measurements. The hydrocells cover 46% of the insole,
which have been arranged to record pressures that Paromed
believes to be the most clinically relevant areas of the
foot. The insole itself is a 2.5 mm-thick sheet of
polyvinyl chloride with the conductive transducers planted
in hydrocells filled with silicon. The hydrocells collect
pressure data and calculate the shoe reaction forces based
on surface area of the sensors. Regardless of where the
hydrocell sensor is compressed, the sensor cell will record
the same measurement. Figures 3.1-3.2 shows the Parotec-

System insoles.

55

CESZ:j~“-‘~_-__~—“\\\
€95) @8009

y .(3
% 9969999 )

4 IL‘! -— V

 

 

37mm

Mm
Hm 24mm
-1 l66mm 7

83mm fiwi

Figgre 3.1. A schematic of the Parotec-System insole (Hsi,
Chai & Lai, 2004)

 

 

 

 

 

 

 

Figgre 3.2. The Parotec-System insole

Two wires are stabilized to the shank (Figure 3.3) and
a controller unit is stabilized around the torso, which

collects the data (Figure 3.4).

56

 

Figgre 3. 3. The Parotec- -System wiring stabilized to the
shank

 

Figgre 3.4. The Parotec-System computer stabilized to torso
The controller unit can store and collect foot
pressure data on a removable PCMCIA compatible memory card.
The insole has a resolution of 2.5 kPa and a range of 600
kPa. Data is recorded between 10-300 Hz. Following data

collection, information collected by the controller unit

57

can be downloaded into a computer using a serial connection
and viewed with the Parotec-System data acquisition and
analysis software.

Although the Parotec—System is a fairly new device, a
variety of studies have been conducted which utilized the
Parotec-System to analyze foot pressures (Arampatzis,
Bruggemann & Klapsing, 2002; Blackwell, et al., 2002;
Chesnin, Selby-Silverstein & Besser, 2000; Goldberg,
Besser, & Selby-Silverstein, ND; Hsi, et al., 2002; Hsi,

Chai, & Lai, 2004; Tillman, Fiolkowski, Bauer & Reisinger,

2002).
Testing Procedures

The control and experimental testing was conducted on
the same day, within a 20-minute time frame. The only
clothing requirement was that the participant had to wear
an athletic shoe, so the Parotec-System insole and Stabil
Lite orthotic could be inserted.

Once written consent was given, a participant
demographics questionnaire was administered. (See Appendix
E). Answers given on the participant demographics
questionnaire can be found in Table 4.2. The following
topics were asked on the demographics questionnaire:

0 Age

0 Weight

58

0 Height
0 Shoe Size
0 Sex

Body part that is painful (multiple answers could be

given)
Physical activities the participant participated in
(multiple answers could be given)
0 Hours per week in those activities
0 Pain during day-to—day activity
0 Pain during physical activity
0 Pain at pre-test
0 Pain at post-test
Once the survey was completed, the proper insoles of
the Parotec-System were fitted to French shoe size and
inserted in the shoe. Next, the computer was stabilized to
the torso, the shoes were placed on the participant, the
sensors were connected to the computer on the torso, and
the wires were stabilized to the shank via Velcro straps.
Prior to the calibration of the Parotec—System in both
the control and experimental conditions, the participant
was instructed to walk around for a few steps to make sure
the insoles were positioned correctly inside the shoe.

Calibration was accomplished by the participant sitting on

59

a chair and lifting their feet off the ground, so they were
non—weightbearing. Additionally, the computer was set to a
dynamic setting at a sampling rate of 60 Hz.

In the non—orthotic (control) condition, the
participant was placed on a straight path and instructed to
walk down the path at normal walking pace. Data collection
began with the right foot. The participant was instructed
to start walking with their right foot. The first two
steps with the right foot were necessary for the
participant to accelerate to their normal gait Speed.

Prior to the third heel strike with the right foot, the
researcher used the remote control to begin data recording.
Data was collected for a total of seven steps in the right
foot. Following the last toe—off of the right foot, the
researcher paused the computer with the remote control.

The participant was instructed to walk back to the starting
point, beginning with their left foot. Again, the first
two steps with the left foot were necessary for the
participant’s normal gait speed to occur. Prior to the
heel contact with the third left step, the computer was
unpaused and data collection resumed. Another seven steps
were recorded, to conclude data collection for that trial.
These procedures occurred five times, resulting in 35 steps

recorded for each foot to be analyzed. Following each

60

trial, the card was taken out of the computer on the torso
and placed into a reader on a laptop, where the data were
saved.

The Stabil Lite orthotic was introduced for the
experimental condition. For this condition, the Parotec—
System insole was placed directly over the Stabil Lite
orthotic to measure the effects the orthotic had on plantar
pressure. Once the orthotic was inserted and the Parotec-
System was placed on the participant and calibrated, the
same walking protocol from the control condition occurred.
The participant walked down the path beginning with the
right foot. After the first two steps, the researcher
began data collection. Data collection occurred in steps
3-9. Next, the participant turned around and walked back
to the starting point, starting with the left foot. After
the first two steps with the left foot, data collection
began in steps 3~9. This concluded one trial. A total of
five trials occurred, resulting in 35 steps recorded for
each foot.

Data Analysis

From the five trials, data were taken from
predetermined sensors via the Parotec-System for Windows
version 4.02.18. The areas that were analyzed were the

metatarsal heads. The cells that were analyzed were cells

61

13—20. The cells that were under the heel were not
analyzed due to 1) the high error rate in cells 1-4 and 2)
low incidence of chronic injury as a result of abnormal
plantar pressures. The medial longitudinal arch (cells 5—
12) and toes (cells 21-24) were not examined also because
of the low incidence of chronic injury as a result of
abnormal plantar pressures.

This group of cells at the metatarsals was divided
equally so there was a lateral half and medial half. Cells
13, l4, l7, and 18 were defined as the “lateral forefoot”
and cells 15, 16, 19, and 20 were defined as the “medial
forefoot”. Figure 3.5 demonstrates the location of the

sensors on the Parotec-System insole.

62

 

all
u 8
DO
Oil

 

 

Figaro 3.5. Parotec-System insole numbering for a right
foot

The Parotec-System data analysis program automatically
computed the mean pressures for each cell for the seven
steps. From each trial, the sum was calculated for each
region of the pressures (ie, cells 15, 16, 19, and 20 were
summed and cells 13, 14, 17, and 18 were summed). The
summed pressures over the five trials in each condition
were averaged and were defined as the average plantar
pressures. (See Appendix A). These data were analyzed for
statistical significance. The average plantar pressures in

each condition were used to calculate a lateral forefoot

63

plantar pressureszmedial forefoot plantar pressures ratio
to quantify plantar pressure distribution during the
control trial and experimental trial. (See Appendix B).
This method of analyzing plantar pressures was derived from
a study by Willis and colleagues (2002). A 1.00:1.00 ratio
demonstrated an even distribution of pressures across the
forefoot. A ratio of less than 1.00 demonstrated increased
pressures on the medial portion of the forefoot. A ratio
of greater than 1.00 demonstrated greater pressures on the

lateral portion of the forefoot.

Chqpter 4: Analysis of Results

Twenty participants

the ages of 18-35

(10 male and 10 female)

between

(mean age: 26.8 years, mean height: 1.8

m., mean mass: 79.1 kg, mean BMI: 24.9, mean French shoe

size: 42.4) were used for this study.

French shoe size was

used in this study so a common shoe measuring system could

be used between both sexes.

calculated as [mass (kg) / height (m)2].

Table 4.1. Participant Demographic Information

Body mass index (BMI) was

(See Table 4.1).

 

. Age Height Mass ,

Subject (yrs) (m) (kg) BMI Shoe Size (Fr) Sex
1 20 1.8 56.7 18.5 38.5 F
2 18 1.5 63.5 26.5 37.5 F
3 30 1.9 79.4 22.5 46.0 M
4 35 1.7 97.5 33.7 40.5 F
5 23 1.7 65.8 22.0 40.0 F
6 23 1.8 63.5 19.5 40.5 F
7 25 1.9 74.8 21.2 46.0 M
8 28 1.9 142.9 38.9 49.5 M
9 34 1.7 56.7 19.6 37.0 F
10 24 1.9 79.4 21.9 48.5 M
11 24 1.8 108.9 34.4 44.5 M
12 23 1.8 72.6 23.6 41.0 F
13 25 1.8 90.7 29.5 40.5 F
14 28 1.7 62.6 23.0 40.0 F
15 35 1.9 83.9 23.8 44.0 M
16 27 1.8 68.0 22.2 41.0 M
17 33 1.7 61.2 22.4 36.0 F
18 22 1.9 113.4 33.0 46.0 M
19 24 1.8 74.8 22.4 44.5 M
20 35 1.9 65.8 19.1 46.0 M

 

Specific questions were asked about the

injury and training regimen.

in the questionnaire about area of pain

participant's

The participants were asked

65

(l—foot,

2—arch, 3-

ankle, 4-shin, S-knee, 6-thigh, 7-spine), activities
participating in (1—run, 2—walk, 3-bike, 4—swim, 5-weight
lifting, 6-aerobics, 7-other), hours per week participating
in the activities, pain day—to-day (Pain D-D), pain during
physical activity (Pain P.A.), pain pre-test (Pain Pre),
and pain post-test (Pain Post) The answers given are

displayed in Table 4.2.

Table 4.2. Participant Characteristic Information

 

Area .
. . . . Bours/ Pain Pain Pain Pain
sub3°°t °5 “mun“ Week D-D P .A . Pre Post
Pain
1 2 1,7 4 3 5 1 O
2 4 1,6 12 2 6 2 2
3 1,5 3,4,7 6 1 2 2 2
4 1,5 1,2,7 8 2 4 O O
5 2,5 1,7 7 4 7 1 1
6 3 1,6,7 8 2 4 3 3
7 4 2 4 4 4 3 3
8 1 1,2,3 6 7 9 6 3
9 1 1 10 0 2 O O
10 5 7 10 2 3 O O
11 3,7 1,4,5 10 O 3 0 O
12 1,4 1,4 6 O 3 O O
13 1 1,2,4 5 4 4 2 2
14 2,6 1,3,5 10 1 4 1 1
15 2,4 2 2 1 3 O O
16 5 1 3 l 3 O 0
17 5 2 5 1 4 l l
1 8 6 2 , 7 3 4 6 5 5
1 9 1 1 , 2 7 1 2 0 0
2O 1 1 12 7 9 7 7

 

66

Statistical Analysis

 

Statistical Analysis Between Pressure.Measurements in
Control and Experimental Conditions

All statistical analyses were performed using the SPSS
statistical software package (version 14.0; SPSS, Inc.,
Chicago, IL). Descriptive statistics were analyzed between
the right and left foot's recorded medial plantar pressures
with and without the Stabil Lite orthotic (See Table 4.3).
A 2(without) x 2 (with) repeated measures ANOVA was
conducted to determine the effect Stabil Lite orthotics had
on plantar pressures in the right and left medial forefoot
compared to baseline readings. Results indicated that
there were no statistical changes in the right medial
forefoot with insertion of the Stabil Lite orthotic versus
baseline measurements (F = 0.022, p = 0.884). There were
also no statistical changes in the left medial forefoot

with insertion of the Stabil Lite orthotic versus baseline

measurements (F = 0.580, p = 0.456). (See Table 4.4).

67

Table 4.3. Descriptive Statistics for Plantar Pressures
Means‘Without and.With Stabil Lite Orthotic In Medial
Forefoot

 

Std.

Time N Mean (kPa) Deviation
Without Orthotic

Right 20 . 484.33 149.90

Left 20 513.31 125.62
With Orthotic

Right 20 482.26 141.58

Left 20 524.00 163.45

 

Table 4.4. Individual 2x2 Repeated Measures ANOVAs
Comparing Medial Forefoot Without and'With Use of Stabil
Lite Orthotic

 

Foot SS df MS F P
Right 42.539 1 42.539 0.022 0.884
Left 1142.013 1 1142.013 0.580 0.456

 

*(significance at the p = 0.05 level)

Descriptive statistics were analyzed between the right
and left foot’s recorded medial plantar pressures with and
without the Stabil Lite orthotic (See Table 4.5). A
2(without) x 2 (with) repeated measures ANOVA was conducted
to determine the effect Stabil Lite orthotics had on
plantar pressures in the right and left lateral forefoot
compared to baseline readings. Results indicated that
there were reductions in the right lateral forefoot
pressures with insertion of the Stabil Lite orthotic versus

baseline measurements (F = 23.822, p = 0.000). There were

68

also reductions in the left lateral forefoot with insertion
of the Stabil Lite orthotic versus baseline measurements (F
= 25.699, p = 0.000). (See Table 4.6).

Table 4.5. Descriptive Statistics for Plantar Pressures

Means'Without and‘With Stabil Lite Orthotic In Lateral
Forefoot

 

. Std.
Time N Mean (kPa) Deviation
Without Orthotic
Right 20 501.05 161.41
Left 20 499.64 120.40
With Orthotic
Right 20 449.33 158.49
Laft 20 447.48 122.40

 

Table 4.6. Individual 2x2 Repeated Measures ANOVAS
Comparing Lateral Forefoot‘Without and‘With Use of Stabil
Lite Orthotic

 

 

Foot SS df MS F P

Right 26747.515 1 26747.515 23.822 0.000*

Left 27199.354 1 27199.354 25.699 0.000*
*(significance at the p = 0.05 level)

Statistical Analysis Between Right and Left Foot’s Plantar
Pressure Ratios

Descriptive statistics were analyzed between the right
and left foot’s plantar pressure ratios with and without
the Stabil Lite orthotic. (See Table 4.7). A 2 (right) x
2 (left) repeated measures ANOVA was conducted to determine

the relationship of the Stabil Lite orthotics in the right

69

and left foot. Results indicated that medial shifts
occurred in the right foot (F = 4.393, p = 0.050) and left
foot (F = 9.593, p = 0.006) compared to baseline readings,
but not for the interaction between the right and left foot
(F = 0.937, p = 0.345). (See Table 4.8).

Table 4.7. Descriptive Statistics for Plantar Pressure
Ratio Means Between R/L Foot

 

Std.
Time N
Mean Deviation

Without Orthotic .

Right 20 1.12 0.42520

Left- 20 1.01 0.28873
With Orthotic

Right 20 0.99 0.32337

Left 20 0.93 0.28785

 

Table 4.8. Individual 2x2 Repeated Measures ANOVAs
Comparing Right and Left Foot With Use of Stabil Lite
Orthotic

 

Foot SS df MS F P

Right 0.154 1 0.154 4.393 0.050*

Left 0.250 1 0.250 9.593 0.006*
Right & Left 9.977 E-3 1 9.977 E-3 0.937 0.345

 

*(significance at the p = 0.05 level)

70

Statistical Analysis Between Genders’ Plantar Pressure
Ratios .

Descriptive statistics were analyzed between the
genders’ plantar pressure ratios with and without the
Stabil Lite orthotic. (See Table 4.9). A 2 (right) x 2
(left) x 2 (gender) repeated measures ANOVA was conducted
to determine the interaction of the Stabil Lite orthotics
in gender compared to baseline readings. Results
demonstrated no significant differences between genders
following insertion of the Stabil Lite between genders (F =
3.497, p = 0.078). The Observed Power for this analysis

was calculated as 0.425. (See Table 4.10).

71

Table 4.9. Descriptive Statistics for Plantar Pressure
RatioiMeans Between Gender

 

Time N Mean Std.
Deviation
Without Orthotic
Right
Male 10 1.27 0.33115
Female 10 0.98 0.47412
Total 20 1.12 0.42520
Left
Male 10 1.13 0.29027
Female 10 0.90 0.24477
Total 20 1.01 0.28873
With Orthotic
Right
Male 10 1.12 0.29752
Female 10 0.98 0.30441
Total 20 0.99 0.32337
Left
Male 10 1.01 0.28371
Female 10 0.84 0.27953
Total 20 0.93 0.28785

 

Table 4.10. Individual 2x2x2 Repeated Measures MOW“
Comparing Mean Pressure Ratios Without/With Orthotic and

Gender

 

SS df .MS F 1) OP
Gender 1.174 1 1.174 3.497 0.078 0.425

Statistical Analysis Between Age Groups’ Plantar Pressure

Ratios

Two age groups were created to analyze the effects the
Stabil Lite orthotic had on age. The median was calculated
from the participants’ ages and was found to be 25 years
old. Participants who were younger than the median age was

placed in the “young group” and participants who were

72

either the median age and older were placed in the “old
group”.

Descriptive statistics were analyzed between the age
groups’ plantar pressure ratios with and without the Stabil
Lite orthotic. (See Table 4.11). A 2 (right) x 2 (left) x
2 (age) repeated measures ANOVA was conducted to determine
significance with the use of the Stabil Lite orthotics on
age compared to baseline readings. Results demonstrated no
significant differences among the age groups (F = 0.154, p
= 0.699) with use of the Stabil Lite orthotics. The
Observed Power for this analysis was calculated as 0.066

(See Table 4.12).

73

 

 

 

 

 

 

Table 4.11. Descriptive Statistics for Plantar Pressure
RatioIMeans Between Age Group
Time N’ Mean Std.
Deviation
Without Orthotic
Right
Young 10 1.06 0.31817
Old 10 1.18 0.50468
Total 20 1.12 0.42520
Left
Young 10 0.94 0.16449
Old 10 1.07 0.35875
Total 20 1.07 0.28873
With Orthotic
Right
Young 10 1.03 0.30993
Old 10 1.18 0.34610
Total 20 1.12 0.32337
Left
Young 10 0.91 0.29732
Old 10 0.94 0.29353
Total 20 0.93 0.28785
Table 4.12. Individual 2x2x2 Repeated.Mbasures ANOVAs
Comparing Mean Pressure Ratios Without/With Orthotic and
Age
88 df IMS F jp OP
Age 6.119 E—2 1 6.119 E—2 0.154 0.699 0.066

 

74

Chapter 5: Discussion

Analysis of Plantar Pressure Data

 

Each participant had their mean plantar pressures
recorded over each trial. The effect the Stabil Lite had
on pressure alteration could be compared from the control
trials to the experimental trials. In this study, 19 right
feet and 17 left feet had reduced lateral pressure with the
use of the Stabil Lite orthotic. Statistical analysis
revealed a significant reduction in lateral plantar
pressure in both the right and left foot with insertion of
the Stabil Lite orthotic. These findings of reduced
pressures in the lateral forefoot are consistent with
previous literature (Donahue et al., 1996; Higbie, et al.,
1998; Hodgson, et al., 2005).

In the medial forefoot, alterations of plantar
pressure were mixed. For the right foot, 14 participants
had their medial pressures decreased and only 9 had medial
pressures reduced in the left foot. Statistical analysis
revealed there was no significant change in medial plantar
pressure with the insertion of the Stabil Lite orthotic.
These results are inconclusive compared to studies by
Donahue and colleagues (1996), Higbie and colleagues
(1998), and Willis and colleagues (2002). Higbie and

colleagues (1998) found that there was a reduction in

75

medial plantar pressures with the use of an orthotic.
Donahue and colleagues (1996) and Willis and colleagues
(2002) found increases in medial forefoot plantar pressures
with use of an orthotic. They attribute this increase in
medial forefoot pressures for two reasons. One, the
composition of the orthotic was harder than the insole of
the shoe, thus reducing shock-absorbing capabilities.
Secondly, the increased arch support in the medial
longitudinal arch resulted in more contact with the foot,
resulting in more forces being absorbed along the first and
second metatarsal.

Decreases in plantar pressures in the midfoot, can be
very advantageous to physically active individuals.
Research has shown that plantar pressures can increase up
to 12% in the midfoot during a fatiguing protocol, which
replicated a bout of exercise (Weist, et al., 2004). This
increase in plantar pressures can predispose individuals to
metatarsal stress fractures if these forces are repetitive
(Boden, et al., 2001; Eils, et al., 2004; Gross & Bunch,
1989; Weist, et al., 2004). According to Boden and
colleagues (2001), there is a high risk for stress
fractures in the second and fifth metatrsals. Thus, an
external device that can offload plantar pressures in these

areas should be desirable to physically active individuals.

76

This study demonstrated that plantar pressures in the
area of the fourth and fifth metatarsals were significantly
reduced with the use of the Stabil Lite orthotic. As a
result, active individuals who experience repetitive high
forces in feet, such as runners, would benefit from using
this device.

Multiple theories can be formulated to why forefoot
pressures were reduced. The first theory is because of the
medial arch support of the Stabil Lite supporting the
medial longitudinal arch. The high arch support would
create an increase in ground contact in the medial
longitudinal arch. The arch support also would act like a
fulcrum proximal to the metatarsal heads.

This aspect of the Stabil Lite mimics the design of a
metatarsal head (met—head) rocker sole. This device is an
addition on a shoe’s sole, which adds a fulcrum proximally
to the metatarsal heads. Its goal is to offload plantar
pressures across the forefoot. Figure 5.1 shows a

schematic of a met—head rocker.

77

 

 

 

 

Figgre 5.1. Met-head rocker sole (Custom Footwear Inc.,
2002).

Although the Stabil Lite is not structurally similar to the
rocker sole, it is possible that the high arch support of
the Stabil Lite acted in a similar manner. If the high
arch support functioned like a fulcrum, then the reduction
in lateral plantar pressures would be explained.

Another possibility of why lateral plantar pressures
were reduced in the forefoot is due to a reduction in
intrinsic musculature activity. If an orthotic supports a
joints’ preferred movement path, then a reduction in muscle
activation will result (Hertel & Olmsted, 2004; Kuppermann,
2005; Nigg, et al., 1999). Less muscle tension results in
a less rigid foot. A less rigid foot should be able to
absorb more forces throughout the structures of the foot.

If the Stabil Lite is encouraging the structures in the
foot to work in their preferred movement path and muscle
tension is reduced, then there should be a reduction in

plantar pressures. This would explain the reduction in

78

plantar pressures laterally, but does not explain the lack
of change in medial plantar pressures.

Muscle activity could have also been altered in the
proximal tissues surrounding the knee and hip. Previous
research found increased EMG levels in the quadriceps,
hamstrings, and gluteus medius with the introduction of
orthotics (Hertel & Olmsted, 2004; Kuppermann, 2005). This
increase in muscle activity around the hip is called the
hip strategy in stability. It results in the stabilizing
musculature around the ankle and foot to be reduced during
activity. Again, reduced musculature in the foot will
result in a more supple foot, which allows for forces to be
absorbed more in the structures of the foot.

The Stabil Lite also could have been effective in
reducing lateral forefoot plantar pressures because of the
deep heel cup acting as a cradle around the calcaneous. In
a study by Ochsendorf and colleagues (2000), they theorize
that the ankle mortise is in a neutral position when using
the orthotics they were testing, due to the orthotic
cradeling the calcaneous. This neutral position in the
ankle mortise results in a reduction in the reliance of
supporting musculature in the ankle and foot for stability.

As previously stated, this reduced muscle activity in the

79

foot will result in a more supple foot, which allows for
more force absorption in the structures of the foot.

Analysis of Pressure Ratios in Control & EXperimental

 

Conditions

 

Plantar pressure ratio calculations demonstrated
almost every participant shifting their pressure
distribution medially with the insertion of the Stabil
Lite. With the insertion of the Stabil Lite orthotics, 19
participants had a significant medial shift of their
plantar pressure ratios in the right foot from 1.12 to
0.99. This change in the ratios signified that the Stabil
Lite was effective in creating almost uniform plantar
pressures across the forefoot.

With the insertion of the Stabil Lite orthotics, 18
participants had their plantar pressure ratios
significantly shifted medially in their left foot from 1.01
to 0.93. This change in the ratios resulted in plantar
pressures being concentrated medially, beyond the desired
1.00 ratio. It is unknown why there was a disparity in
ratios between the two feet.

This shifting of pressure ratios was not caused by a
change in medial plantar pressures. Results did indicate
that there was a significant reduction in lateral plantar

pressures. This reduction laterally would in effect reduce

80

the total ratio, resulting in the plantar pressures to be
concentrated medially.

Similar results of a medial shift in plantar pressure
ratios were found in a study by Willis and colleagues
(2002). In this study, the authors analyzed the plantar
pressure distribution of a medial orthotic using a
medialzlateral ratio. The authors found a 0.76 M:L ratio
for the control condition (or 1.316 L:M ratio) and a 0.84
M:L ratio (or 1.190 L:M ratio) for the experimental
condition. The authors concluded that the orthotic was
effective in increasing peak medial load in the patients,
which also created a more uniform plantar pressure. The
one aspect that the authors did not mention in their study
was the effect that the orthotics had on the actual plantar
pressures. Their increase in peak medial load could have
also been the result of a reduction in lateral plantar
pressures.

Analysis Among Genders

 

Analysis between males and females revealed
interesting findings. In analyzing the mean pressure
ratios, the data showed both males and females shifted
their plantar pressures medially with the insertion of the
Stabil Lite. In addition, the left foot demonstrated

plantar pressure ratios more medial than the right foot.

81

Lastly, it was found that females had overall higher medial
pressure ratios compared to males in both the control and
experimental conditions.

Males had reduced pressures medially in seven right
forefeet and five left forefeet, as well as reduced
pressures laterally in all ten right forefeet and nine left
forefeet. Females did not exhibit a reduction in pressures
as frequently as males. Females had reduced pressures
medially in six right forefeet and five left forefeet, as
well as reduced pressures laterally in nine right forefeet
and eight left forefeet.

Although there seemed to be a difference between males
and females when looking at L:M plantar pressure ratios,
statistical analysis revealed no significant differences
between the genders. When considering anatomic differences
between genders, it would not be surprising if there were
statistical differences. Females anatomically tend to
have wider pelvises, to allow for childbirth. This widened
pelvis results in a higher Q-angle at the knees. An
increase in Q—angle places the calcaneous in an everted
position, which results in the foot having more contact
with the ground medially. It would then appear that
females could have a greater concentration of plantar

pressures medially then males. Is possible that the low

82

observed power altered the significance, due to a low
sample of participants. If a greater number of
participants were used, then the changes between males and
females could possibly have been significant.

Analysis Among Age Groups

 

The next analysis was between the two age groups.
Again, groups were formed as being either younger than the
median or older than the median. First, it was seen that
the Stabil Lite orthotics shifted the plantar pressure
ratios medially in both groups. Second, the younger group
was more medially dominant with their plantar pressures
compared to the older group. Lastly, the left forefoot
showed more plantar pressures medially oriented compared to
the right forefoot.

Data analysis revealed there was no significant
interaction with the insertion of the Stabil Lites between
age groups. This can be attributed to the participants
being very comparable in age. There are not a lot of
anatomical and physiological differences among individuals
between the ages of 18—35 years old, especially since this
was a physically active population. It can only be
speculated what kinds of changes may have been seen with

the comparison of participants in a wider spectrum of age.

83

Clinical Implications

 

The data and statistics demonstrate that the Stabil
Lites significantly shifted the plantar pressures of the
forefoot medially compared to baseline conditions. The
Stabil Lites were also effective in reducing lateral
forefoot plantar pressures. This should be seen as a
potential prevention/treatment for active individuals who
may be at risk for metatarsal stress fractures, especially
in the fifth metatarsal. Research has demonstrated that
increased plantar pressures predispose individuals for
metatarsal stress fractures (Boden, et al., 2001; Eils, et
al., 2004; Gross & Bunch, 1989; Weist, et al., 2004). If
there is a reduction in the lateral plantar pressures with
the use of the Stabil Lite orthotic, then less force will
be absorbed in the metatarsals, thus potentially decreasing
injury rate.

Another aspect of the Stabil Lite that is clinically
relevant is the high arch support could increase plantar
cutaneous receptor activity and potentially reduce injury.
As concluded by Hertel, Gay, and Denegar (2002),
individuals with pes cavus feet have a reduced degree of
postural stability, creating an instable base of support
and potentially predisposing individuals for lateral ankle

sprains. They theorized that this was due to a lack of

84

cutaneous sensation from reduced surface area on the
plantar surface. If individuals with pes cavus are making
more contact with the ground through the Stabil Lite, then
plantar cutaneous receptors should process more information
to keep the base of support more stable, thus reducing
injury.

Sources of Measurement Error

It was attempted to record 7 full steps for each
trial. This was done by having a testing protocol that
analyzed one foot at a time. If the researcher was too
quick or too slow in starting the remote to the Parotec-
System, then part of a step would not be completely
recorded or an extra part of a step could be recorded.
This should not alter the data too significantly, since
averages are being calculated over multiple steps.

Also, because the testing was done in the middle of
the store, customers were free to walk through the testing
site. This often would skew the participant from walking
in a completely straight line. If the participant had to
veer severely to avoid a customer, then the trial was nixed
and a new one was started.

It was observed in participant 10 that sensor 16 in
the right foot gave a reading of 0 kPa for every trial.

This was an unexpected finding, since the Stabil Lite

85

clearly covered this sensor, which should give a pressure
reading. As a result, it is theorized that that sensor has
some defectiveness in it. There were no other participants
who used this insole, since the size was rather large, so
this theory cannot be compared to any other test. The
participant’s data was not omitted, due to their resultant
data being comparable to the other participants.

Considerations for the Future

 

The main suggestion for future research would be to
study exactly what constitutes “good pressure
distributions” and “bad pressure distributions”. Although
this study did not find equal distributions of pressures
across the forefoot, it may not be a negative thing.
Clarity is necessary to determine what calculated ratio
increases individuals’ chances of developing an injury. At
this point, it is only hypothesized that an equal
distribution of pressures would be considered Optimal,
since no part of the foot would receive higher stresses
compared to another (Franco, 1987; Kaufman, et al., 1999;
Kitaoka & Patzer, 1997; Manoli, 2001; Neely, 1998; Omey &
Micheli, 1999; Weist, Eils & Rosenbaum, 2004). But, the
pressure ratios tended to shift to a medial dominance with
the Stabil Lite intervention in this study. It would be

erroneous to think that the Stabil Lite negatively affect

86

feet. To analyze this puzzle, long-term studies are
necessary to track injury rates. Through a population of
healthy individuals, it would be beneficial to track any
lower extremity injuries and see if any correlations exist
with laterally/medially dominant plantar pressures.

As previously stated, biomechanical changes that
orthotics induce is debated. Digital imaging techniques,
such as MRI and CT scan should be performed to determine if
structural changes occur with the use of prefabricated
orthotics during static stance and dynamic movements.
Another method of analyzing biomechanical alterations is
videography analysis. Anatomical markings can be digitally
tracked to see biomechanical changes in the body. It would
be especially effective to compare changes made among
individuals who clinically are hyperpronators and
hypersupinators.

Research should continue analyzing the effectiveness
of not only the Stabil Lite orthotic, but also the
effectiveness of other prefabricated orthotics. Currently,
there is limited research on prefabricated orthotics, so
contributions to the literature can be beneficial. If more
studies find comparable outcomes of prefabricated orthotics
to custom~molded orthotics, then health care costs to

manage lower—extremity injuries should be decreased.

87

As the study progressed, the manufacturer released a
full-length Stabil Lite orthotic. Instead of the Stabil
Lite being cut off at the metatarsal heads, it stretched
the full length of the shoe. It would be beneficial to
compare the two types of Stabil Lites, analyzing if there
are any differences between the models.

Additionally, it would be beneficial to see whether or
not the Stabil Lites are an effective treatment to reduce
plantar pressures in individuals with a high body mass
index (BMI). It has been suggested that individuals with a
higher body mass exhibit higher plantar pressures under the
metatarsal heads and medial longitudinal arch (Dowling,
Steele & Baur, 2004). Because our society is continuing to
increase in obesity levels, it is important to develop
devices that can reduce injuries that these individuals may
develop.

The last consideration for future research would be to
use a greater number of participants. Previous literature
utilized between 6-20 participants when using the Parotec-
System, which influenced the decision to collect data from
20 participants in this study. This low number of
participants resulted in a lower observed power. To
increase the observed power score, it would be wise to use

more participants in future studies.

88

Limitations to the Study

 

Although the Parotec-Device has been proven to be an
effective method to analyze plantar pressures in previous
research, some limitations exist in the study. Although
the method of analyzing the data was adapted from previous
studies, the detail in which they were analyzed were not
given. Thus, the effectiveness of how the data was
analyzed can be debated.

One factor that was decided not to control was the
shoe selection of the participant. The only requirement
was that the participant had to wear an athletic shoe
during the study. Although this eliminated boots and dress
shoes from the study, certain shoes are designed to
limit/enhance pronation or supination through stiffness in
the soles. This in effect would lead to some biomechanical
correction without even using an orthotic. Additionally,
older shoes lose shock-absorbing capabilities. This could
possibly increase plantar pressures at areas of excessive
wear in the soles.

Conclusions

 

0 The Stabil Lite orthotics were effective in reducing
lateral forefoot plantar pressures. This could be an
effective device in reducing stress fractures in the

fifth metatarsal.

89

The Stabil Lite orthotics did not equally distribute
the plantar pressures as was hypothesized. The
pressures that were concentrated medially in the
forefoot may not necessarily be a negative outcome
from the orthotic, since some individuals had a
decrease in medial plantar pressures.

The significant increase in plantar pressure ratios
medially can be a result from a significant reduction
in lateral plantar pressures.

There were no significant differences in changes with
plantar pressure ratios among males and females.
There were no significant differences in changes with
plantar pressure ratios among the two age groups.
This can be attributed to the two groups being similar

anatomically and in physical activity.

90

APPENDIX A

Participant Mean Pressure Data

91

Raw Data for Medial Forefoot Plantar Pressure Means

 

Right Medial

Left Medial

Forefoot Forefoot
Subject Without With Net Without With Net
Orthotic Orthotic Change Orthotic Orthotic Change
(kPa) (kPa) (kPa) (kPa) (kPa) (kPa)
1 622.82 588.60 -34.22 595.86 589.65 -6.21
2 630.57 629.32 -1.25 649.50 642.72 -6.78
3 446.07 442.43 -3.64 394.57 398.78 -4.21
4 280.14 450.65 +170.51 479.87 506.38 +26.51
5 549.17 452.58 -96.59 549.12 426.72 -122.40
6 424.50 421.50 -3.00 439.95 473.79 +33.84
7 394.82 365.68 -29.14 416.29 392.51 -23.78
8 614.59 590.46 -24.13 574.09 538.57 -35.52
9 565.94 559.53 -6.41 590.17 597.58 +7.41
10 309.26 263.00 446.26 387.05 330.25 -56.80
11 784.25 773.47 -10.78 829.63 953.65 +124.02
12 297.90 306.46 +8.56 301.40 227.59 -73.81
13 622.53 628.32 +5.79 678.50 724.56 +46.06
14 469.45 492.96 +23.51 481.07 439.09 -41.98
15 421.30 526.64 +105.34 561.48 607.92 +46.44
16 477.40 558.92 +81.52 390.64 454.50 +63.86
17 680.65 621.74 -58.91 572.71 682.31 +109.60
18 481.00 391.57 -89.43 525.66 623.57 +97.91
19 415.86 378.29 -37.57 485.29 530.14 +44.85
20 198.28 203.13 +4.85 363.36 339.66 -23.70

 

92

 

 

Raw Data for Lateral Forefoot Plantar Pressure Means

 

Right Lateral Left Lateral

Forefoot Forefoot ,
Subject Without With Net Without With Net
Orthotic Orthotic Change Orthotic Orthotic Change
(kPa) (kPa) (kPa) (kPa) (kPa) (kPa)
1 324.93 278.35 -46.58 426.18 283.64 -142.54
2 458.72 451.49 -7.23 475.89 442.22 -33.67
3 571.35 561.00 -10.35 534.93 511.28 -23.65
4 563.76 592.77 +29.01 682.97 678.14 -4.83
5 486.55 455.91 -30.64 439.13 419.29 -19.84
6 484.59 451.71 -32.88 473.18 485.50 +12.32
7 287.93 230.00 -57.93 382.72 294.06 -88.66
8 701.39 511.14 ~190.25 606.44 509.48 -96.96
9 454.68 388.59 -66.09 459.59 394.52 -65.07
10 386.44 327.50 -58.94 406.53 289.63 -116.90
11 971.11 918.59 -52.52 808.05 731.23 -76.82
12 454.77 401.18 -53.59 338.87 309.64 -29.23
13 492.51 469.78 -22.73 534.71 485.59 -49.12
14 387.83 344.51 -43.32 419.71 391.86 -27.85
15 565.56 534.54 -31.02 463.89 467.83 +3.94
16 715.12 668.64 -46.48 677.53 546.38 -131.15
17 347.28 316.84 -30.44 353.72 357.90 +4.18
18 610.34 459.39 -150.95 584.97 564.00 -20.97
19 368.00 308.71 -59.29 430.57 366.01 -64.56
20 388.14 316.00 -72.14 493.14 421.46 -71.68

 

93

 

 

APPENDIX B

Participant Mean Ratio Data

94

 

 

Descriptive Statistics for Mean Right & Left Forefoot
Plantar Lateral:Medial (L:M) Pressure Ratios Without and
With Orthotic

 

Right Forefoot Left Forefoot
Subj ect Without With Pressure Without With Pressure
Orthotic Orthotic . Shift Orthotic Orthotic Shift
1 0.52 0.47 * 0.72 0.48 *
2 0.73 0.72 * 0.73 0.69 *
3 1.29 1.27 * 1.36 1.28 *
4 2.03 1.32 * 1.43 1.35 *
5 0.89 1.01 ** 0.80 0.98 **
6 1.14 '1.07 * 1.09 1.09 *
7 0.74 0.63 * 0.92 0.75 *
8 1.15 0.87 * 1.06 0.95 *
9 0.81 0.70 * 0.78 0.66 *
10 1.27 1.26 * 1.05 0.89 *
11 1.24 1.19 * 0.98 0.77 *
12 1.54 1.31 * 1.13 1.12 *
13 0.80 0.75 * 0.79 0.67 *
14 0.83 0.71 * 0.87 0.89 **
15 1.35 1.02 * 0.83 0.77 *
16 1.53 1.20 * 1.78 1.25 *
17 0.51 0.51 = 0.62 0.53 *
18 1.27 1.17 * 1.12 0.91 *
19 0.90 0.82 * 0.89 0.69 *
20 1.96 1.61 * 1.36 1.24 *
MEAN’ 1.13 0.99 * 1.02 0.93 *

 

Key: * (Medial Pressure Shift)
** (Lateral Pressure Shift)
= (No Pressure Shift)

95

 

APPENDIX C

University Committee for Research Involving Human Subjects
(UCRIHS) Approval Form

96

VA

 

OFFICE OF
REGULATORY
AFFAIRS

MAI. 8 HEALTH
INSTITUTIONAL REVEW
BOARD (BIRD)

cowuuurrr neswzca
Immoral). REVEW
BOARD (came)

SOCIAL SCENCEJ
IBIAVDRAL I EDUCATION
NSTWUWAL REVIEW
BOARD (SIRE)

202 Olds Hal

Easl Unsung. Muchlgan
48824—1046
517-355-2180

Far 517432-4503

w humanresoerchmsu sou
SIRE 8| SIRS: lRqumsu ecu
CRIRB: mmu ggy

NSU u an ajmuw «at-mm
equal-opportunity rmmwrm

MICHIGAN STATE

 

UNIVERSITY

Initial IRB
Application
Approval

March 23. 2006

TO‘ John POWELL
105 IM Spons Circle
MSU

Re. IRB 9 06-194 Category: EXPEDITED 2-4. 2-6
Approval Date: March 23. 2006
Expiration Date: March 22. 2007

Tulle: AN ANALYSIS OF PRESSURE DISTRIBUTION WITH A PREFABRICATED FOOT ORTHOTIC

The Instllullonal Revlaw Board has completed their review 01 your project. I am pleased to advise you that
your proloct has been approved.

The committee has found that your research project is appropnate in design. protects the rights and welfare
01 human subpcts. and meets the requirements of MSU‘s Federal Wrdo Assurance and the Federal
Guldellnes (45 CFR 46 and 21 CFR Pan 50). The prolecfion 01 human sub)ects in research 13 a partnership
between the IRS and the investigators. We look forward to working with you as we both fulfill our
responsibilities. .

Renewals: IRB approval is valid until the expiration date listed above. ll you are continuing your project. you
must submlt an Application for Renewal application at least one month before explratlon. If the project ls
completed. please submit an Application for Permanent Closure.

Revuslons: The IRS must revlew any changes an the project. prior to initiation of the change. Please submit
an Application («Revision to have your changes reviewed. It changes are made at the time of renewal.
please lnclude an Application for Rsvlslon with the renewal application.

Problems: I! issues should arise during the conduct of the research, such as unanllclpaled problems.
adverse events. or any problem that may Increase the risk to the human subjects, notrry the IRB ollrce

promptly. Forms are available to report these issues.

Please use the IRB number listed above on any terms submitted which relate to this project. or on any
correspondence wllh the IRB office.

Good luck In your research. If we can be of further assistance. please contact us at 517-355-2180 or via

email at IRB@m§Q.QQ. Thank you for your cooperation.

Sincerely.

/’ ’fl
/€V}~—A—

Peter Vasilenko. PhD.
BIRB Chair

\/ Wlllram Vascik

4326 Dell Rd.
Apt. 6
Lansing, MI 48911

97

APPENDIX D

Human Subjects Consent Form

98

 

 

An Analysis of Pressure Distribution With A Prefabricated Foot Orthotic

Informed Consent

For questions regarding this study, For questions regarding your rights
please contact: as a research participant, please contact:
Dr. John Powell, ATC Peter Vasilenko, PhD.

Michigan State University Committee on Research Involving Humans
Phone: (517) 432-5018 Michigan State University

E-mail: powellifilarmsucdu or 202 Olds Hall

 

East Lansing, MI 48824
E-mail: uchrih@msu.cdu
Phone: (517) 355-2180
Fax: (517) 432-4503

William J. Vascik, ATC
Graduate Assistant
Michigan State University
E-mail: vascikwiajmsucdu
Phone: (814) 360-0186
Work: (517) 490—2645

The purpose of this study is to examine the pressure distribution across the sole of
the foot while using an insert in your shoe. The orthotic that will be introduced is called
a Stabil-Lite and is produced by Playmakers Athletic Footwear & Apparel in East
Lansing, MI. To measure the pressure distribution, a portable pressure insole system,
called the Parotcc-Systcm (Paromed Medizintechnik GmbH, Neubeuern, Germany), will
be used inside your shoe.

You have agreed to the following criteria to be a potential participant in the study:
I) having no lower extremity injury within the past year, 2) no previous surgery in the
lower extremity, 3) no uncorrectable-visual or balancing problems. 4) are between the
ages of 18 and 35 years-old, and 5) have not used an orthotic device or insert for the past
six months. If you are willing to participate, you will be asked a few demographics]
questions, as well as questions relating to your injury. Next, your navicular drop will be
measured, which classifies your foot type. This is done by the most prominent pan of
your navicular bone in your foot being marked. The height of this mark is recorded on an
index card while you are partial weightbearing. You will stand normally and the mark
will be rcrecordcd. The distance will be measured to determine the total navicular drop.
Navicular drop <5 mm is considered a high arched foot, navicular drop between 5-10 mm
is considered a “normal foot”, and a navicular drop >10 mm is considered a flat foot. as
defined in the literature.

Your participation in this study will consist of one ISO-minute testing period to be
conducted in Playmakers Shoe Store. Professionals who are familiar with the equipment
being used will supervise the study. Additionally. there will be a certified athletic trainer

This consent form was approved by the Biomedical and Health Institutional Review Board (BIRB) at Michigan State
University Approved 0323/06 - valid though 03/22I07. This version supersedes all previous versions. IRB ii 06-194.

99

(ATC) on site in case of a medical emergency or injury. We will use connection wires
that are directly plugged into a portable computer around your waist and Velcro straps on
your leg will stabilize the wires. Once the insoles have been selected according to your
shoe size. they are placed inside your shoe. There are 24 hydrocells imbedded in the
insole system, which directly record pressures from your feet throughout the experiment.
The computer is then stabilized around the torso with a belt. Once the computer is
stabilized, the wires from the leg are connected to the computer.

Prior to data recording, you will have two minutes to walk around with the insole
from the Parotec-System in your shoe. You will feel some cushioning under your foot.
This walking around is for the insole to conform under your foot. The control protocol
will have you walk down a runway 8 steps with each foot at your normal walking pace,
turn around and walk 8 steps with each foot back. The first three steps are necessary for
your walking speed to become normal. The other 5 steps will be recorded via the
Parotec-System. There will a total of 5 cycles of this for the control protocol. Once these
cycles have ended, we will begin testing your pressure distribution with the introduction
of Playmakers Stabil-Lite orthotic. This device looks like a harder variation of the insole
in your shoe, with an increased heel cup depth, lateral wall, and increased arch support.
During these trials, you will feel the Stabil-Lite under your foot. Although the orthotic
may feel slightly uncomfortable, it should not be painful. You may feel an increase in lift
in your arch and/or cradling around your heel. Once the orthotic is inserted, the same
procedures will take place as before. Following these trials, you will be asked to evaluate
your pain while wearing the Stabil Lites and provide any comments on the study or
inserts.

It is impossible for the risk of injury to be completely eliminated during the trials.
Although you should not feel any pain as a result of the insertion of the insole or orthotic
or the computer stabilized around the torso, it is possible to get your legs tangled in the
wiring that emits from the computer. This risk is minimized with the wiring being
stabilized around your leg. In case of injury, a certified athletic trainer (ATC) will be on
site to manage the injury. ‘

The benefits that come from your participation will help further advancements in
understanding the effect that prefabricated orthotics have on an injured population as it
relates to plantar pressure distribution. Following the conclusion of the testing, your
results will be provided for you in a printout. as well as impressions from the printout.
Additionally. it will give the medical community more information on the Parotec-
System, which is a relatively new device for research.

Participation in this study is voluntary. Your identity and information recorded
during the study will remain confidential. Confidentiality will be protected by; (8) results
will be presented in aggregate form in any presentations and publications; and (b) all data
will be stored in a computer that has a password necessary to see confidential data. Your
privacy will be protected to the maximum extent allowable by law. You may also
discontinue participation at any time without penalty. Your participation in this research
project will not involve any additional costs to you or your health care insurer.

This consent form was approved by the Biomedical and Health Institutional Review Board (BIRB) at Michigan State
University. Approved 03/23/08 - valid though 03/22/07. This version supersedes all previous versions. lRB 13 06-194

100

If you are injured as a result of your participation in this research project,
Michigan State University will assist you in obtaining emergency care, if necessary, for
your research related injuries. If you have insurance for medical care, your insurance
carrier will be billed in the ordinary manner. As with any medical insurance, any costs
that are not covered or are in excess of what are paid by your insurance, including
deductibles, will be your responsibility. The University’s policy is not to provide
financial compensation for lost wages, disability, pain or discomfort, unless required by
law to do so. This does not mean you are giving up any legal rights you may have. You
may also contact Dr. John Powell at S l 7-432-5018 with any questions or to report an

injury.

Any questions concerning participation in this study should be directed to
William J. Vascik at 814360-0186 or Dr. John Powell at 517-432-5018. If you have
questions or concerns about your rights as a research participant, please feel free to
contact Peter Vasilenko, Ph.D., Director of the Human Subject Protection Programs at
Michigan State University: (5 1 7) 35 5-2180, fax: (517) 432-4503, email: irb msu.edu, or
regular mail: 202 Olds Hall, East Lansing, MI 48824.

 

INFORMED CONSENT .
Your signature below indicates your voluntary agreement to participate in this study.
1, have read and agree to participate in this study as
(Please Print Your Name)
described above.

 

(Please Print Your Name)

/ /

(Date)

 

 

(Please Sign Your Name)

Witness

 

(Please Prml l'our Nu me)

I r’
I I

(Dare;

 

 

(i’icuse .S'igu Your Name)

This consent form was approved by the Biomedical and Health Institutional Review Board (BlRB) at Michigan State
University. Approved 03123106 - valid though 03/22/07. This version supersedes all previous versions. tRB ti 06-194.

101

APPENDIX E

Participant Demographics Form

102

Participant
An Analysis of Pressure Distribution With A Prefabricated Foot Orthotic
Participant Intake Questionnaire\

Circle “yes” if the following questions apply:

Are you between the ages of 18 and 35 years old? Yes No
Have you ever had an orthopedic surgery in the lower extremity? Yes No
Do you have any non-correctable visual and/or balancing problems? Yes No

Have you previously used any type of orthotic (custom or store bought), arch support, or
other type of insert in your shoe? Yes No

If you answered “yes” to number 4, please answer questions 5-8:
Are you wearing them currently? Yes No

If not, when did you stop wearing them? <1 month ago 1-6 months ago >6 months ago

 

 

How often do you wear them? 1-2 days/week 3-5 days/week 6-7 days/week
What kind are they? Custom Off-the-Shelf Brand:

FOR OFFICE USE ONLY

Eligible for Participation? Yes No

103

Participant

An Analysis of Pressure Distribution With A Prefabricated Foot Orthotic

 

 

 

 

Participant Demographics
Age:
Weight:
Height:
Shoe Size:
Sex: Male Female

What area of the body has been painful?

Hip Thigh Knee Shin Calf
Ankle Arch Foot Toes Low Back
Other

 

What physical activities do you participate in during a normal week?

Running Walking Basketball Volleyball Wrestling Soccer Tennis
Swimming Ice Hockey None Other:

 

How many hours do you participate in the activity a
week?

 

Rate your pain, 0 being no pain and 10 being extreme pain during day-to-day activity:

 

 

1 2 3 4 5 6 7 8 9 10
Rate your pain, 0 being no pain and 10 being extreme pain during physical activity:

1 2 3 4 5 6 7 8 9 10
Pre-T est

Rate your pain, 0 being no pain and 10 being extreme pain now:

1 2 3 4 5 6 7 8 9 10
Post-T est

Rate your pain, 0 being no pain and 10 being extreme pain while using the Stabil Lites:
1 2 3 4 5 6 7 8 9 10

What comments do you have relating to the testing procedure or Stabil Lite orthotics?

 

 

104

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114

   

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