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thesis entitled

COMPUTER-ASSISTED THREE-DIMENSIONAL
GAIT ANALYSIS OF AMPHOTERIClN-INDUCED
EQUINE CARPAL LAMENESS

presented by
John Gerard Peloso

has been accepted towards fulfillment

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Masters Science

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June 12, 1992
Date

 

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’ I P - ll, In

COMPUTER-ASSISTED THREE-DIMENSIONAL
GAIT ANALYSIS OF AMPHOTERIClN-INDUCED
EQUINE CARPAL LAMENESS

By

John Gerard Peloso

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Large Animal Clinical Sciences

1992

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I

ABSTRACT

COMPUTER-ASSISTED THREE-DIMENSIONAL
GAIT ANALYSIS or AMPHOTERICIN-INDUCED
EQUINE CARPAL LAMENESS
By

John Gerard Peloso

Using six clinically sound horses trotting at 4.0 m/s on a treadmill, motion was
captured using a computerized three-dimensional motion analysis system before
and 9, 16 and 23 days after lameness induction to determine: the efficacy of three-
dimensional computer-assisted image analysis for objective lameness evaluation
in horses and the quantitative variables which significantly describe this lameness.
The dorsal vertical distance travelled by the head (HE) and withers (WE) was
increased significantly during all lameness measurement periods when coupled to
the sound forelimb. HE but not WE was decreased significantly during all lameness
measurement periods, when coupled to the support phase of the lame forelimb.
Computer determinations of stride length, stance phase, forelimb abduction, carpal
and fetlock range of motion did not significantly characterize the lameness. It was
concluded that three-dimensional computer-assisted image analysis could be used
for objective lameness evaluation in horses and that head and withers excursion

were reliable variables for the assessment of equine carpal lameness.

DEDICATION

To my parents Donna Marie and Dino Ferdinand Peloso for
your attention to the essence of life and your love
while you shared these philosophies.

ACKNOWLEDGEMENTS

To Dr. John Stick for your guidance, your drive to be the best and your endless
store of energy.

To Dr. John Caron for providing perspective by teaching me to challenge the
accepted.

To Dr. Robert Soutas-Little for introducing me to the discipline of Biomechanics
and Dr. Charles DeCamp for your theoretical assistance during this project.

To Drs. Frank Nickels and Fred Derksen for your instruction throughout my
residency.

To Troy Trumble for your technical assistance. Your unsolicited participation often
went beyond what was reasonable.

To Dr. James Belknap, because the trail you blazed forced me to explore my zone
of discomfort. ‘

To my best girl, Dr. Margo Macpherson. Your strength has allowed our
relationship to outlast the physical, financial, emotional and time restrictions of a
residency. I feel a tremendous enthusiasm for our future.

TABLE OF CONTENTS

LIST OF TABLES
LIST OF FIGURES
CHAPTER
I. INTRODUCTION
ll. LITERATURE REVIEW ON LAMENESS ASSESSMENT
A. Development of Motion Analysis
B. Alternate Motion Analysis Techniques
C. Assessment of the Lame Horse
D. Equine Arthritis Models
Ill. PRINCIPLES OF MOTION ANALYSIS
A. Introduction
8. Orthogonal Coordinate System
C. Direct Linear Transformation

D. Retro-reflection

Ease
vii

viii

11

13

17
17
18

21

TABLE OF CONTENTS (CONT)
VI. MATERIALS AND METHODS
A. Horses
B. Experimental Design
C. Measurement Technique
a. Room Design
b. Clinical Determination of Lameness
c. Coordinate System
d. Calibration Procedure
e. Target Locations
f. Data Acquisition and Reduction
9. Data Processing and Variables Assessed
D. Statistical Analysis
VII. RESULTS
VIII. DISCUSSION

IX. SUMMARY AND CONCLUSIONS

LIST OF REFERENCES

vi

21

24

26

27

28

30

31

32

37

59

62

LIST OF TABLES

Protocol followed to induce arthritis and evaluate lameness.

Lameness scale from the AAEP Definition and Classification of
Lameness.84

X,Y and Z coordinates of the 16 control point calibration structure
used to define the reference coordinate system origin and
coordinate directions.

Anatomic location of reflective targets fixed to subjects during
data acquisition.85

Representative baseline data of computer generated three- ‘
dimensional poll target coordinates demonstrating the sinusoidal
increases and decreases of the Z coordinate (even frames). The
formulae used in the average value calculation for head rise
coupled to the left (i) forelimb support phase and the right

(ii) forelimb support phase appears below.

The effect of amphotericin-B induced arthritis on stride length,
stance phase, carpal and fetlock range of motion, forelimb
abduction, head and withers excursion are listed in the following
order: the sound limb then the lame limb. All values are presented
as means (Xi SEM). (#=range of motion, *=p50.05 *i" = p50.01)

vii

23

26

28

31

33

4O

LIST OF FIGURES

The geometric representation of the intersection equations used to 20
used to determine the unique three dimensional location (X,Y,Z) of
point 0 in object space. Image plane 1 and 2 represent the
perspectives of each camera to object O. The object reference
system has origin A and coordinate directions n,,,ny and n2 while

the camera reference systems have origin B and digitized coordinate
axes U and V with the digitized values of l1 (U,,V1) and I2 (U2,V2).

The value of the camera coefficients, namely A1 to L1 and A2 to L2,
are known and are determined during calibration. The values of U,,V1
and U.‘,,V2 are also known and are determined from the digitized
coordinate axes U and V. Therefore, the values of X,Y,Z are the
remaining unknowns and can be determined by solving the four
equations shown.”81

Topographic arrangement of laboratory used for data acquisition. 25
Equipment used included a treadmill (TR), computer (00), computer
cameras (01.02.03.04), calibration strings (81.82.8354),

calibration stand (CS), target control points (CP1,0P4,CP5,CP13),

object reference coordinate directions (REF) and positions where video
camera images were collected for subjective evaluation (V1,V2).

The mean (XiSEM) subjective lameness scores as determined by two 37
independent examiners during baseline measurements (B) and 9,16,

and 23 days post induction of arthritis. Examiners used the AAEP
lameness classification scale.EM (**=P_g_0.01)

viii

LIST OF FIGURES

Representative vertical displacement (Z component in cm) .of

the head (target 1) and left front hoof (target 8) as horses

trotted (4 m/s for 6 seconds) on the treadmill. a) Recording of
head movement before arthritis induced (horse 1). b) Recording of
head movement post arthritis induction for a 3/5 subjective
lameness grade (horse 4). c) Recording of head movement post
arthritis induction for a 4/5 subjective lameness grade (horse 2).

Stance phase (XiSEM in seconds) of the sound forelimb and
the lame forelimb before (B) and 9, 16, and 23 days after the
lameness induction.

Forelimb abduction (XiSEM in degrees) of the sound forelimb and
the lame forelimb before (B) and 9, 16, and 23 days after the
lameness induction.

Stride length (X_+_SEM in cm) of the sound forelimb and the lame
forelimb before (B) and 9, 16, and 23 days after the lameness
induction.

Carpal range of motion (Xi-SEM in degrees) of the sound forelimb
and the lame forelimb before (8) and 9, 16, and 23 days after
the lameness induction. (**=P_<_0.01).

Fetlock range of motion (XiSEM in degrees) of the sound forelimb
and the lame forelimb before (B) and 9, 16, and 23 days after the
lameness induction. (*=P_go.05 **=P5_0.01).

EQQQ

39

43

45

47

10.

11.

LIST OF FIGURES

Withers excursion (XiSEM in cm) initiated during the support phase
of the sound forelimb and the lame forelimb before (B) and 9, 16,
and 23 days after lameness induction. (*=P50.05).

Head excursion (XiSEM in cm) initiated during the support phase
of the sound forelimb and the lame forelimb before (B) and 9,
16, and 23 days after lameness induction. (*=P_<_0.05, **=P$0.01).

Page

43

49

I. INTRODUCTION

Abnormalities of the equine musculoskeletal system are the leading cause for
performance loss in the equine athlete” and the main reason why equine
veterinary services are requested.‘ It has been recommended that research on
the equine musculoskeletal system assume a high priority 2'5 because lameness
has been documented as the most significant factor causing wastage among
young racehorses.“3 Despite these recommendations, few objective lameness
studies have been performed on horses.“3

Locomotion has been defined as all the biomechanical events that occur while
an animal or person moves from one place to another in a controlled and
deliberate manner.9 Biomechanics can be subdivided into statics, the effects of
forces on bodies at rest, and biodynamics, the study of bodies in motion with
reference to the forces and masses involved.1o Biodynamics is further subdivided
into biokinetics, the study of forces acting on bodies to produce motion, and
biokinematics, the geometric description of motion without reference to forces. A
comprehensive biomechanical evaluation includes measurements of relative or
absolute body segment motion changes (biokinematics), a study of forces acting

on bodies to produce these motions changes (biokinetics) and an analysis of the

2
electrical activity of the muscle, (electromyography “ in order to document which

muscles are responsible for the specific forces and motion noted at a given point
in the stride cycle.

This project is concerned exclusively with biokinematics, the temporal and
geometric characteristics of motion without regard to the associated forces or
muscles involved. Extensive reports on the different technologies available for
quantitatively assessment of motion have been published.9"2'15

The main objective in this study was to determine if computer-assisted three-
dimensional video gait analysis technology currently used in human medicine
could be used to objectively evaluate lameness in horses. Our specific objectives
were: 1. To determine what quantitative variables could be used to assess
lameness in the horse and 2. To determine which of these variables most reliably

provide assessment of equine carpal lameness.

ll. LITERATURE REVIEW ON LAMENESS ASSESSMENT
A. Development of Motion Analysis

Review of the literature suggests that the earliest investigation into quadruped
limb motion was likely conducted by Aristotle.16 The first reported study of
photogrammetry (the science of obtaining reliable measurements by means of

photography) was conducted by Muybridge in 1872. Muybridge, a photographer

3
in California, was sponsored by Leland Stanford to photograph the various phases

of a horse’s gait to determine the most scientific method for training a race horse,
and so began the age of quantitative motion assessment. A series of 24 cameras,
with exposures of 2/1000 of a second, were set at right angles to the track and line
of motion. The horse broke a thread as it trotted by and tripped the shutter in
each camera.17 In an 1878 Scientific American article, Muybridge indicated that
the vertical lines in the background of his photographs are separated by 28
inches. Knowing that his subjects trotted at a speed of 2 minutes and 24 seconds
per mile, it allowed the captured motion to be analyzed. He proved that the
walking horse always has two feet on the ground, and for a brief moment three.
He revealed that the stride length of a trotting horse increased 4 fold compared
to a walk and while trotting, the horse is completely off the ground for half the
length of the stride."3

When the first motion picture camera was introduced in 1923, photogrammetry
became a viable research tool.‘9 In 1939, quantification of human athletic
performance was improved by using the multiplier technique.20 As sprinters
travelled perpendicular to the cameras optical axis, motion was quantified by
placing a bar of known length in the filming sequence. Knowledge of this length
combined with the measured length of the corresponding image provided a single

multiplier coefficient and allowed quantitative measurements to be derived from the

4

films.20 In 1960 Kaemmerer used photogrammetrics to improve the description of
limb flight in horses by attaching lights to the distal aspect of their limb.21 Though
these changes helped simplify the work involved in quantifying the images seen,
motion assessment was still limited to a plane perpendicular to the cameras optical
axis. In a 1967 human kinematic research trial, Noss used three cameras located
precisely along three orthogonal (mutually perpendicular) axes to overcome the
problem of perspective error. He believed that perpendicular optical axes with a
common point of intersection could be used to derive accurate three dimensional
position data.22 Thirteen years passed before this simple method, devised to
correct for camera perspective errors, was proven to be invalid.23

In 1972 Fredricson and Drevemo described a system for quantitative analysis
of equine locomotion using high speed film in order to derive kinematic data. They
also provided a technique for three-dimensional analysis of joint movement while
filming Standardbreds at speed.2"27 Correcting problems associated with camera
perspective errors, precise camera orientation before filming and hours of pre-test
set-up time were rectified in 1971 by Abdel-Aziz and Karara.28 These ideas were
modified to include orientation constants from the camera interior and then
developed for human clinical biomechanics assessment in 1981 by Dr. Jim Walton
as part of his Ph.D. project at Pennsylvania State University.29 By using a

technique known as direct linear transformation (DLT), the above mentioned

5

authors removed all restrictions in camera placement and relative orientation.

In recent years,advances with motion assessment have included the
development of cameras with higher speeds and better image resolution, fully
digitized photogrammetric systems, improved image processing and analysis. As
well, computer software packages with integrated image processing and three
dimensional graphic systems have been designed to provide real time data

acquisition.30

B. Alternate Motion Analysis Techniques
1. Visual Lameness Assessment

In 1985, the reliability of observational kinematic gait-analysis was evaluated
using a three point scale on 15 children that wore a bilateral knee-ankle-foot
orthoses due to lower limb disabilities.31 Three experienced and highly trained
clinicians, who had received prior training on the three point scale, evaluated these
children on two occasions. The second ratings occurred thirty days after the first.
In this study, self-agreement occurred 69% of the time and between-rater
agreement occurred, 67.5% of the time. It was concluded that substantial
variability exists among and between trained specialists in the visual assessment
of lameness, making this technique unreliable.31

Similarly, visual assessment techniques were used in ponies and shown to be

6

unreliable. Ponies that had been previously evaluated on a force plate received
an intratendinous injection of collagenase to create inflammation in the superficial
digital flexor tendon. After nine months, the force plate measurements were
repeated and were combined with clinical examination for lameness by an
experienced clinician. All three groups were rated as clinically sound by the
clinician but the force plate was able to distinguish between performances that had
returned to normal and those which had compensated and therefore appeared
sound.” Consequently, measurement systems which generate quantitative

information that can be analyzed are preferred over visual assessment techniques.9

2. Kinematic Analysis Systems
a. Cinematography and Videography
The techniques available include single camera photography, multiple camera
photography, 8mm movie cameras”, high-speed movie projectors and video
cameras. Though limited quantitative information can be retrieved from these
systems, they provide a permanent record that can be subjectively evaluated.13
A 16mm high-speed camera is the system most frequently used in equine gait
analysis laboratories. The advantages of a 16 mm camera are its ability to provide

a permanent record and yield large amounts of information without altering the

7

movement of the horse. However, because the film plane must be perpendicular
to the line of travel of the horses,7 and course markers have to be exactly spaced,
preparation times are excessive. Additionally, errors caused by moving skin
markers,“"""'35 delays in film processing,13 equipment expense?” and the labor
involved in film analysis7'15 further complicate this technique. Two or more high-
speed cameras may be used from different vantage points to photograph the
horse, but this practice is limited to laboratories where more than two or three
strides can be collected.38 Three dimensional analysis is possible using high
speed cinematography, but is usually done in two dimensionsx'a" because
cameras need to be synchronized making set up complex.” An alternate method
was used to collect more than three strides of data per filming session. This
involved following the subject around a race track with a camera mounted to a
moving vehicle.‘°""27'38

The advantages of videography are similar to high speed cinematography; they
provide a permanent record, a great amount of information and data collection
does not alter the normal movement of the horse. They are also easier to operate,
allow immediate play back and the videotapes can be re-used.‘2"3 Unfortunately
video cameras have poor image resolution.“13 In an effort to improve resolution,

cameras may be moved closer to the subjects but have their field of view

decreased. These video cameras are expensive, and similar to all situations where

8

targets are fixed to moving subjects, errors can occur due to marker movement.9

b. Automated Optical Systems

Optical systems capable of automated movement analysis are available.
Improved camera perception of target location, when compared to 16 mm
cinematography, is facilitated by using infra-red light emitting diodes or retro-
reflective colored prisms. Transmitted light is perceived by cameras and sent to
a digitizer which rapidly converts the position of markers on the subject into X &
Y coordinates. The computer accepts the X,Y coordinates from the digitizer and
assimilates the data for analysis. Since light emission is essential for target
recognition, these systems are restricted to the laboratory where extraneous
sources of light are omitted.“
c. Electrogoniometry

In 1977 Adrian et al used electrogoniometers (electrical instruments) to examine
angle changes of the metacarpophalangeal joint in four Thoroughbreds. 39'”
Electrogoniometry consists of an elgon (electrogoniometer), an amplifier and a
recorder.37 The elgon is a potentiometer that functions as an electrical protractor.
Initially, the elgon is calibrated on a protractor and mounted over the center of
rotation of the joint to be evaluated. The chassis and electrical leads are then

taped to the leg and connected to an amplifier attached to the subject. Changes

9

in joint angles are recorded as the horse moves at the selected gait. The
goniograms may be analyzed manually or digitized and analyzed by a computer.
Goniometry has been used in the normal“ and clinically lame horse.3° It has been
used to assess motion of the fetlock, hook and carpus," and provides direct,
continuous recording of joint motion from horses moving at all gaits. It has the
disadvantages of being difficult to accurately locate and secure over the center of
rotation of the joint, particularly in the proximal aspect of the limbs due to skin
movement. Because few joints move in a single axis, these devices may restrict
normal joint movement due to the planar nature of the chassis and the methods

used to secure it to the limb.“

3. Kinetic Analysis Systems
a. Force Platforms

Force platforms were originally developed for the horse in 1976 by Pratt and
O’Connor,42 and have since become the standard for kinetic measurements. They
are composed of a hardened aluminum upper surface with underlying strain
gauges or piezoelectric crystals which produce force measurements. A force
platform is designed to quantify the magnitude, direction and duration of a ground
reaction force (GRF). The GRF is comprised of three forces, the vertical forces(Fz),:

cranio-caudal forces(Fy) and medic-lateral forces (F,,).8 The variability inherent in

10

locomotion has caused people to recommend a minimum of 25 trials per test
period for humans and a minimum of 30 for horses.” In horses, an average of
one in 20 passes by the force plate delivers an adequate foot strike” making this
system very time inefficient.
b. Equine Kaegi Gait Analysis System

The Kaegi Gait Analysis System has electromagnetic field sensors below its
upper surface. These sensors are connected through a series of fluid-filled tubes
to piezoelectric crystals. The hydraulic impulse created by the weight of the horse,
is translated into an electric signal by the piezoelectric crystal which is proportional
to the vertical force from the limb.43 This system is limited in its usefulness since
it measures vertical forces only12 and cranio-caudal horizontal force have proven
to be useful in lameness diagnosis.”
c. Accelerometers

Accelerometers are small device that attach to a body or limb segment to
measure its acceleration. A piezoelectric crystal detects and quantifies the
acceleration of movable parts in the accelerometer and send a signal proportional
to that acceleration. By selecting a uni,bi or triaxial accelerometer, one two or
three axes of motion can be evaluated.” Accelerometers do require cables to be

attached to the horse and therefore may interfere with normal motion.7

d. Instrument Shoes

Instrument shoes (force shoes) capable of measuring vertical, or vertical, medio-
lateral and cranio-caudal force measurements are available.12 These shoes use
one or more piezoelectric force transducers attached to a racing shoes to detect
force changes. Cables from the transducers extend from the shoes up the limb
to instruments necessary for modifying and storing the signal.” Force shoes can
measure consecutive strides of the trot, canter or gallop and enable the collection
of data from a perfect "strike" every stride. They can be attached to all four limbs
to obtain a more complete force profile while a lighter (aluminum) design has
allowed gait evaluation at high speeds to be performed safely. They are currently
not used as a clinical tool since the shoes have to be fitted and nailed to the foot

for accuate data acquisition.

0. Assessment of the Lame Horse.

Though quantitative reports describing the lame horse are uncommon,°'“ it is
hypothesized that the symmetric nature of animals and humans allow asymmetries
in individual gait to be identified as lameness.° This hypothesis was tested by
Drevemo et al using 30 clinically sound trotting Standardbreds.“5 It was
demonstrated that limb movement variations in any particular horse were very

small when assessing stride length, and the duration of stride, stance, swing and

11

12

propulsion.

Unilateral lameness in the trotting horse is subjectively thought to produce
changes in both the timing (eg stance phase) and distance in limb movement (eg
stride length) .4519 A stride is defined as a cycle of Iocomotor events which begin
with the stance phase of a particular limb and ends with the subsequent stance
phase of that limb.”O Stride length is conventionally defined as the horizontal
distance covered along the plane of progression during one stride.“5° In the
normal horse, stride length increases linearly with velocity through the complete
velocity range.‘51 Stance phase is defined as the time period when the limb is in
contact with the ground.9'5° It appears that potential stride modifications between
subjects are inconsistent, for example; when comparing stance phase times
between sound and lame limbs, published reports have shown it to be unaffected,8
decreased47 and increased.”-49

Changes in the vertical position of a horses head and neck, which together
comprise approximately 10% of their body weight,” has been the standard in
forelimb lameness evaluation. In the original Lameness in Horses by Dr. Adams
he states, "As a result of lameness in a forelimb, the head will drop when the
sound foot landsf"3 These beliefs are summarized in the fourth edition of
Stashak’s dams' Lameness in the Horse: “Typically for the forelimbs, the horse

drops his head down on the sound limb and raises it up to a more normal height

13

on the affected side" and "At a trot the lameness becomes obvious and some
head and neck lifting occurs when the affected limb hits the ground".“
Explanations for the change in head and neck position include an attempt to
reduce the weight bearing on the affected limb“ and an effort to shift the center
of gravity caudally, away from the lame forelimb, as the head is elevated.6
Several quantitative force platform analyses have been conducted in unilateral
models of forelimb lameness.°'55'5° Changes associated with compensatory
unloading of the lame limb have been uniformly demonstrated. The injured
forelimb of walking or trotting horses have decreased vertical forces, decreased
cranio-caudal decelerative horizontal forces, with no change in the cranio-caudal
accelerative forces. The contralateral sound forelimb has shown no change in the
vertical forces, increases in the cranio-caudal decelerative forces and decreases
in the cranio-caudal accelerative forces?” Contact time (stance phase) averaged
around 242.8 msec for both the sound and lame limb and was not affected by the
induction of lameness.8 Comprehensive kinematic studies on the lame horse are

not available?“

D. Equine Arthritis Models
A diarthrodial or synovial joint contains the ends of two articulating surfaces of

bone that are covered with hyaline cartilage, a soft tissue joint capsule that

envelopes these structures and synovial fluid that fills the joint space. The joint
capsule has a fibrous outer layer and an inner synovial layer. This synovial layer
lines the joint space and contains synoviocytes which secrete synovial fluid.”

Arthritis, or osteoarthritis, is literally translated to mean inflammation of the joint.
The expression degenerative joint disease (DJD) is now used synonymously with
all forms of osteoarthritis,” and represents a group of disorders charaCterized by
alteration of the articular cartilage and accompanying changes in the bone and soft
tissues of the joint.”

Though use-trauma is considered to be the most important initiating factor in
DJD,” the inciting cause for DJD is unknown and includes the following theories;"’8

1. Primary soft tissue inflammation.

2. Cyclic fatigue damage to the collagen network in cartilage.

3. Trauma causing microfractures in the subchondral bone which subsequently

stiffens and results in decreased shock absorption and cartilage degeneration.

Primary synovitis is characterized by inflammation of the synovium without
articular cartilage damage and results from physical or chemical damage to the
soft tissue as would occur by repeated overextension.“o Secondary synovitis
occurs as a result of trauma to or degeneration of the articular cartilage or
subchondral bone. The interaction between synovium and articular cartilage is

complex and incompletely understood, but it is known that structural and functional

14

15

alterations in one tissue intimately affects the other."0

Osteochondral fractures of the equine carpus are common in racehorses,““
and in particular, those horses that train and race on a dirt track.”‘” Horses
having carpal arthropathy may be temporarily or permanently removed from
training or racing, but accurate diagnosis and appropriate therapy is associated
with a favorable prognosis for return to racing with figures of 79 % in one report
and 80 % in another.”'66 In this project, arthritis was induced in the middle carpal
joint because the carpus is associated with a high incidence of injury,”'°5 and has
been the major focus of objective arthritis and lameness relate research.55'°7'” To
develop a greater understanding of equine arthritis and to quantitate different
treatment modalities, both physical and chemical regimens have been used to
induce joint inflammation.

Arthritis has been physically induced by creating osteochondral fractures
on the dorsomedial aspect of both radial carpal bones,75 and by creating partial

67” and full thickness defects in cartilage, then subjecting these horses to

exercise.“””
Osteoarthritis has been chemically induced using several different agents.
Using 0.5mls of Freund’s complete adjuvant, Hamm et al produced a carpal

arthritis to study the effects of an intra-articular medication. Arthritis was

characterized by local swelling, pain and an increase in synovial protein.7o Hurtig

16
et al injected 10 mg of autogenous femoral trochlear cartilage into the left middle

carpal joint and then exercised horses, anticipating a more authentic arthritis. The
model was characterized by a mild synovial effusion, capsulitis and transient
lameness.” Alternatively, 50 mg of sodium monoiodoacetic acid has been used
to produce articular cartilage degeneration, periarticular swelling and synovial
effusion.”'”'7° Firth injected E. Coli lipopolysaccharide into the middle carpal joint
of 6 ponies and created articular effusion, pain on flexion, increases in synovial
rotein, total leukocyte and neutrophil numbers and a lameness that lasted 36
hours.72 Amphotericin-B was selected to induce arthritis in this project because the
polyene antibiotics, amphotericin-b73 and filipin 7‘, had been used previously to
induce synovial arthritis in horses.

Amphotericin-B functions as an antifungal’”8 by forming an irreversible bond
to ergosterol, the principal sterol in the cell wall of fungal organism.78 Leakage of
potassium ions and other intracellular components result in the eventual lysis of
sensitive fungi. Amphotericin-B binds less aggressively to cholesterol, the principal
sterol of mammalian cell membranes, and therefore has a reduced effect on animal
tissues.78 Filipin-induced arthritis has been observed to disrupt synovial cell
lysosomes and increase acid phosphatase activity in synovial fluid thereby
producing an inflammatory arthritis.73 Amphotericin-B has also cause a marked

and persistent increase in acid phosphatase activity in synovial fluid and it is

17

theorized that, like filipin, the mechanism of induced arthritis is due to disruption
of synovial cell lysosomes." These effects are beneficial since synovial lysosomal
enzymes, rather than damaged articular cartilage, are the major contributor to the

lysosomal content of equine synovial fluid.73

III. PRINCIPLES OF MOTION ANALYSIS
A. Introduction

In this project, data acquisition and reduction utilized established biokinematicc,
photogrammetrics, anatomy, science, mathematics, physics, optics and
sophisticated computer technology and software packages. The sections that
follow are provided to give the reader a better understanding of the pertinent
aspects of these disciplines as they relate to this thesis. More exhaustive
explanations are available in the references provided.
B. Orthogonal Coordinate System

A reference coordinate system, including an origin and coordinate directions, is
required to measure the position of bodies in space. All locations in the reference
system indicate a position relative to the origin while movement reflects changes
in position closer to, around, or further away from the origin. Since a reference
coordinate system should span the space of interest, three non-coplanar

coordinate directions need to be selected.79 Calculations are greatly simplified

18
when the axes are orthogonal” (mutually perpendicular) and therefore a right

handed orthogonal coordinate system with axes labeled X,Y,Z was utilized. This
orthogonal system is useful when examining vectors81 '” since their components,
or the magnitude of the vector in the X,Y, or 2 direction, is simply the projection

(the cosine) of the vector on the coordinate axes.1o

0. Direct Linear Transformation

Direct linear transformation (DLT) requires advanced filming of at least six non-
coplanar control points to generate a set of twelve equations per camera?”1 This
a priori filming of the non-coplanar points, known as calibration, provides control
points that are measured values from a previously assembled and exactly
measured calibration structure. Each set of DLT equations contain terms that
define the image and object coordinates of each control point as well as eleven
calibration coefficients. These coefficients contain absolute information regarding
camera orientation, lens to image plane distance, and the linear components of
lens and image distortions.2"'7""31 Knowledge of the known object and measured
image coordinates for each control point provide the user with an overdetermined
system of twelve equations with eleven unknowns. A linear least squares
technique is used to approximate the values of the calibration coefficients.”78

At least two image planes (cameras) are needed to yield precise estimates for

19

the location of a point in three dimensional space, so a second set of DLT
equations are generated for these control points as viewed by a second
camera.”'7"'78 Again using the known object (calibration structure) and measured
image coordinates of each control point, calibration coefficients can be
approximated for this second camera.

Since each object point has a unique (X,Y,Z) location in space, these two sets
of equations provided by two camera perspectives, can be combined provided
they are time matched. This combination of equations is known as the intersection
equation and is analogous to the intersection of two principal optical rays at the
location of the object at point ’0’ (Figure 1).”81

The three-dimensional spatial coordinates of unknown targets placed in the
space encompassed by the calibrated structure are determined by way of a direct
linear transformation using the four (or more) DLT equations (two from each
camera) and the two dimensional image coordinates established from each image

(camera) plane.81

These four equations with three unknown spatial coordinates
are again overdetermined and a least squares technique is again used to provide
an estimate of their location. This estimate can be improved by increasing the

number of cameras used at different vantage points.2"'79'81

1

U - A,X+B,y+C,Z+D, U - A2x+Bzy+C2z+Da
2

 

 

'- E,x+F,y+G,z+1 - sz+Fzy+Gzz+1

I-I,x+J,y+K,z+L, _ Irl,x-I-.I,y+l<,z‘I-L2

 

 

E,x+F,y+G,z+1 - Eax+F2y+Gzz+1

\

 

 

 

 

 

 

 

\
\ u, / N2

Image Plane 1 Image Plane 2

Figure 1. The geometric representation of the intersection equations used
to determine the unique three dimensional location (x,y,z) of point 0 in

object space. Image plane 1 and 2 represent the perspectives of each
camera to object O. The object reference system has origin A and
coordinate directions n,,,n,,,nz while the camera reference systems has
origins B and digitized coordinate axes U and V with the values of I,,(U,,V,),
and l2, (U2,V2). The values the 11 camera coefficients, namely A, to L, and
A2 to L2 are known and are determined during calibration. The values of
U,,V, and U2,V2 are also known and are determined from the digitized
coordinate axes U and V. Therefore, the values x,y,z are the remaining
unknowns and can be determined by solving the four equations shown.”-°‘

D. Retro-reflection

The exact location of limb and body segments are facilitated by attaching light-
emitting targets to exercising subjects. Targets can be covered by a retro-
reflective tape and therefore intensify their identification.” With mirror reflection,
a beam of light is reflected at an angle equal and opposite to the angle of
incidence. With diffuse reflection a beam of light is reflected in all directions, and
reduces the intensity of light transmitted. By using a retro-reflective surface on
targets two optical principles can be exploited, namely cube corner and spherical
bead lens reflection.” These phenomenon cause reflected light to be transmitted
directly to the original source of light and provide a reflective efficiency 50 to 3000
times that of white light.” When target brightness is sufficient, supplementation

through electrical wires, which can interfere with normal gait,12 is not needed.

VI. MATERIALS AND METHODS
A. Horses

Six adult mixed-breed horses [meanL-LSEM); body weight 388(_t8.3 kg), age
3.2(i0.64 yrs)] were used in this study. All animals were maintained on a 1 acre
pasture for 30 days prior to experiments and were vaccinated against equine
influenza, rhinopneumonitis, and tetanus. All animals were dewormed with an

anthelmintic and shown to be sero-negative for equine infectious anemia. The

21

22
horses were determined to be suitable subjects based on the results of a

pre-study health examination. The health examination included a rectal
temperature, pulse, respiratory rate, complete blood count and serum chemistry.
A lameness examination, including radiographs of both carpi,(including a flexed
Iateromedlal, dorsolater-palmaromedial oblique and dorsomedial palmarolateral
oblique) was also performed. The horses were trained to walk for 1 minute at 1.8
m/s and to trot for 2 minutes at 4.0 m/s once a day for three days on a high speed
treadmill“. Horses exhibiting lameness either during the initial examination or after
treadmill training were removed from the study. During the acclimation and

measurement phases of the study all animals were housed in individual stalls.

B. Experimental Design

Baseline motion data was recorded on both computer disk and video tape on
day one (Table 1). Following this, all animals received an intra-articular injection
of 20 mg of amphotericin-Bb in 5 mls of sterile water in the left middle carpal joint.
This was repeated using 25 mg of amphotericin-B in 5 ml of water on day 3 and
day 5 of the protocol. Phenylbutazone° at the dose of 2.2 mg/kg was given orally

once, after the first amphotericin-B injection, to control animal discomfort.

 

a Mustang 2000, ngra AG, Fahrwangen, Switzerland.
b. Funglzone, ER Squibb 8: Sons Inc., Princeton, NJ.
c. Butszolldin Paste, Coopers Animal Health Inc., Kansas City. KS.

23
Additionally, 0.1 mg/kg of butorphanol tartrated was given intramuscularly every 6

hours for the first 24 hours or longer to effect. The butorphanol injections were
repeated on days 3 and 5 of the protocol. Motion data was recorded on both
computer disk and video tape on days 9, 16, and 23. At the end of the study
each horse was euthanized using an intravenous barbiturate overdose in
accordance with the guidelines established by the Animal Care Committee at

Michigan State University.

Table 1. Protocol followed to induce arthritis and evaluate lameness.

 

Day Procedures

1 Ma‘, Video“, Ampho’, sz@, Butor“
3 Ampho, Butor

5 Ampho, Butor

9 Ma, Video

16 Ma, Wdeo

23 Ma, Euthanasia

MA = Computer motion data acquired

Video = Video camera images collected
Ampho = Infra-articular amphotericin-B injected
sz = P.O. phenylbutazone administered
Butor = I.M. butorphanol injected

 

d. Torbugeslc, Fort Dodge Laboratories, Fort Dodge, IA

B. Measurement Technique
a. Room Design

All data acquisition took place at Michigan State University Equine Performance
Center in an area depicted in Figure 2. Four 60 hertz cameras' and their
accompanying light sources were placed symmetrically around the treadmill. The
cameras were arranged to capture the images from reflective spheres on trotting
horses, then co-axial cable ported the information to the video analyzer'. These
images were converted, by the video analyzer and a computer work station“, to
four files of two dimensional data. A portable video camera", positioned at V1 and

V2 (Figure 2), was used to videotape each trial for subjective

 

evaluation.

e. T1-23A 00d, NEC Corp., Tokyo, Japan.

f. VP320, Motion Analysis Corp., Santa Rosa, 0A.

9. Spare Station 1, Sun Microsystems Inc., Mountain View, CA.
h. SK-FZOOK. Toshlba Corp., Denver, CO.

24

25

REF

 

 

 

 

 

 

II S,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2. Topographic arrangement of laboratory used for data acquisition.
Equipment used included a treadmill (TR), computer (00), computer
cameras (01.02.03.04), calibration strings, (31.32.8354) calibration stand
(CS). target control points (0P1, 0P4, 0P5, CP13), object reference
coordinate directions (REF) and positions where video camera images were
collected for subjective evaluation (V1, V2).

b. Clinical Determination of Lameness

As horses trotted on the treadmill at 4 m/s, sixty seconds of videotape was

collected for each horse from point V1 and V2 (Figure 2). Two independent

observers evaluated the videotapes and graded horses on a scale of 1-5 using an

accepted lameness scale (Table 2).”

Table 2.

Definition:

Lameness scale from the AAEP Definition and Classification
of Lameness.”

Lameness is a deviation from the normal gait or posture due
to pain or a mechanical dysfunction.

Classification Grades:

Difficult to observe;not consistently apparent regardless of
circumstances (i.e. weight-carrying, circling, inclines, hard
surfaces,etc.)

Difficult to observe at a walk or in trotting a straight line;
consistently apparent under certain circumstances (i.e. weight
carrying, circling, inclines, hard surfaces,etc.)

Consistently observable at a trot under all circumstances.

Obvious lameness: marked nodding, hitching or shortened
stride.

Minimal weight-bearing in motion and/or at rest;inability to
move.

26

27

Lameness scores from each viewer were added by testing period and divided
by the number of lameness evaluations (6 horses x 2 evaluators) to arrive at the
mean (XiSEM) lameness score for that testing period.

0. Coordinate System

An orthogonal coordinate reference system was established and became an
integral part of the calibration structure and the calibrated space used in this
project. The origin was defined as being twenty five centimeters below control
point 1 (Figure 2, Table 3) at the intersection of the treadmill belt surface and
calibration string one. Three mutually orthogonal axes, X,Y,Z, were used to define
the reference space and are described below. The positive X-axis of the
coordinate system was defined as being coincident with the vector extending from
control point 1 to 5 on the calibration structure. The positive Y-axis of the
coordinate system was defined as being coincident with the vector extending from
control point 1 to 13 and the positive Z-axis of the coordinate system was defined
as being coincident with the vector extending from control point 1 to 4 on the

calibration structure.

Table 3. X,Y, and Z coordinates of the 16 control point calibration
structure used to define the reference coordinate system origin and
coordinate directions.

 

Calibration Control X(cm) Y (cm) 2 (cm)
String Point
1 0 0 25
1 2 0 0 75
3 0 0 140
4 0 0 190
5 290 0 25
2 6 290 0 75
7 290 O 140
8 290 0 190
9 290 101 25
3 10 290 101 75
11 290 101 140
12 290 101 190
13 0 101 25
4 14 0 101 75
15 0 101 140
1 6 0 1 01 1 90

d. Calibration Procedure

Calibration provides the necessary coefficients for direct linear transformation
(DLT) so the unknown three dimensional positions of subject targets can be
determined during subsequent motion. The 16 control point calibration structure

(Figure 2) supplied the minimum 6 non-coplanar control points required to perform

28

DLT.”

The structure was made of 15 cm diameter PCV piping in a table shape to
facilitate its placement and removal from the treadmill. Conventionally, control
points should fully encompass the object space where the anticipated motion will
occur, so control points on calibration strings were suspended around the
perimeter of the structure.”'”

The calibration structure was raised to the supporting arms of the treadmill and
the volume calibrated each day before data was acquired. The volume contained
by the calibration strings was verified using a tape measure. It was measured and
adjusted until it contained 290 cm in the X direction, 101 cm in the Y direction and
190 cm in the 2 direction as seen in Table 3. Four, 3.5 cm diameter, spheres were
suspended by each calibration string at distances of 25, 75, 140 and 190 cm
respectively, beginning at the treadmill surface and working in a positive Z
direction. The 16 suspended spheres were covered in retro-reflective tape' to aid
in their identification during data acquisition. The four calibration strings were
numbered counterclockwise (Table 3). Six seconds of data were collected in two
separate trials and assimilated at a work station using computer software‘ with
three-dimensional capabilities. The precision of the testing

equipment was routinely validated during the calibration procedure since sixteen

 

i. No. 7610 High grain sheet, 3M Center. St Paul, MN.
j. Expert Vision-30, Motion Analysis Corp., Santa Rosa, CA.

30

control points were used when only six were needed. The known volume of the
calibrated space (5.56 ms) was determined from the product of length x width x
height. Actual measured distances between targets on the calibration structure
are also estimated by the motion analysis system. The overall difference between
these values give a measurement of error known as the norm of residuals. To
consistently provide accurate three-dimensional target location values, the
calibrated space was adjusted until the norm of residuals were below 5 pixels in
this 5.56 ms volume. Care was taken not to move or jar the cameras once the
calibration procedure was complete since any change in camera orientation
relative to the initial placement of the calibration structure would make future DLT
calculations completely erroneous.
e. Target Locations

Retro-reflective targets were fixed to the subjects to improve limb segment and
joint identification (T able 4).” The targets were made from 3.5 cm spheres
covered in retro-reflective tape. Targets were placed over areas with minimal soft
tissue covering to limit soft tissue motion and close to the instant center of rotation
of each joint to optimize the kinematic information obtained from the
metacarpophalangeal joint and the carpal joint complex.34 Hair was removed from
the areas specified in Table 4 to improve target adhesion and to allow placement

of targets at identical locations for all video taping sequences. Targets were fixed

31
to the horses using 5 cm elastic bandage material which encircled the leg at each

location. This technique eliminated target without restricting limb movement.

Table 4. Anatomic locations of reflective spheres fixed to trotting

subjects during data acquisition.”

Target Number Target Location

 

Squamous Part of Occipital Bone (Pole)

Left Rostral Facial Crest

Right Rostral Facial Crest

Dorsal Thoracic Spinous Processes (Withers)
Left Proximal Lateral Radial Tuberosity

Left Styloid Process of Distal Radius

Left Distal Lateral Tuberosity of Metacarpus Ill
Left Distal Lateral Hoof

Right Proximal Lateral Radial Tuberosity

10. Right Styloid Process of Distal Radius

11. Right Distal Lateral Tuberosity of Metacarpus Ill
12. Right Distal Lateral Hoof

.QSPNQS’TPP’NT‘

f. Data Acquisition and Reduction
Orientation of the treadmill, subjects, videocameras and the object reference
coordinate system can be obtained from Figure 2. Once targets were applied,

subject coordinates direction were defined similar to the calibration structure. As

32

horses trotted on the treadmill at 4 m/s, sisty seconds of video data was collected
by a hand held video recorder (from V1 and V2) for future subjective lameness
evaluation. Quantitative data were acquired by the four symmetrically placed
cameras as the subjects trotted for 6 seconds at 4 m/s. The horse was walked
at 1.8 m/s while the computer assimilated the first trial of video data, then a second
6 seconds of trotting data was acquired at 4 mls. Four files of two- dimensional
data were processed at a computer workstation to produce one file of three
dimensional data for each horse during each trial period.
h. Data Processing and Variables Assessed

Seven variables were assessed in this project: stance phase, forelimb abduction,
stride length, carpal range of motion, fetlock range of motion and withers and
head excursion for both sound and lame limbs. During these six second trials,
numeric values increased and decreased in a sinusoidal fashion (Table 5), since
the variables were measured an average of ten times. Mean values were
calculated by summing the differences between maximums and minimums and
dividing by the number of cycles during that trial. A sample calculation appears
in Table 5. The average values were calculated in an identical manner for all
variables evaluated and will be referred to as the average value calculation. These
were expressed in degrees (joint angles), centimeters (excursions) or seconds

(stance phase).

Table 5. Representative baseline data of computer generated three
dimensional poll target coordinates demonstrating the sinusoidal increases
and decreases of Z coordinate (Even frames). The formulae used in the
average value calculation for head rise coupled to the left (i) forelimb
support phase and the right (ii) forelimb support phase appears below.

PATII FRAME THE X Y 2
“El! UMBER sec cu cm on
1 54 0.003 245.5105 47.0739 166.6692
1 56 0.917 244.9152 47.7014 166.2245 *1- a
1 50 0.950 244.0967 47.6546 166.5306
1 60 0.9a 245.0040 47.4349 167.5976 Left form-b
1 62 1.02 244.5557 47.1966 169.1236 in stpport
1 64 1 .05 243.7454 47.0070 170.4760
1 66 1.00 243.2917 46.9300 170.9129 11* b
1 60 1.12 243.5264 46.3090 170.3011
1 70 1.15 243.9352 45.4907 169.0642
1 72 1.10 243.0799 44.5564 167.6629
1 74 1 .22 243.4957 43.4350 166.5460
1 76 1.25 243.3143 42.1972 166.1405 11* c
1 70 1.20 243.6100 41.1100 166.6010
1 00 1.32 243.7592 40.6015 167.0391 Right forellltb
1 02 1.35 243.2722 40.7005 169.4671 in support
1 04 1.30 242.7300 41.0920 170.7420
1 06 1.42 242.6022 41.0477 171.0273 1* d
1 00 1.45 243.0912 40.0791 170.7120
1 90 1.40 243.6101 40.9660 169.5092
1 92 1.52 243.0729 41.2753 160.0004
1 94 1.55 244.0097 41.5005 166.0166
1 96 1.50 244.4490 41.6661 166.4403 *1- e
1 90 1.62 245.1632 41.7742 167.0022
1 100 1.65 245.4401 42.3674 160.4000 Left forelilb
1 102 1.60 245.2071 43.3400 160.9710 in support
1 104 1.72 245.0560 44.2240 170.0994
1 105 1.73 245.0190 44.5060 170.3645 n f
1 106 1.75 244.9219 44.6990 170.3215
1 100 1.70 244.2479 44.0050 169.4507
1 110 1.02 242.9720 44.0920 167.9905
1 112 1.05 241.0440 44.7231 166.4141
1 114 1.00 241.3463 44.3363 165.1517
1 116 1.92 241.2020 44.0160 164.7210 1* g
1 110 1.95 240.6676 44.1590 165.3257
1 120 1.90 239.7712 44.4910 165.3257 Right forelilrb
1 122 2.02 230.9394 44.0324 166.6044 in support
1 124 2.05 230.0179 45.0400 160.2590
1 126 2.00 237.0015 44.9137 169.3972
1 120 2.12 236.2530 44.9646 169.6510 *1- 11
1 b- + - + II. |(d-c) + (h-g) +....|
O i
n n

* n equals event frequency.

33

34

The sinusoidal progression of numbers produced for carpal range of motion
(carpal joint complex), fetlock range of motion and forelimb abduction were
derived identically by taking the scalar product between the vectors formed, as
defined by target positions. A vector is defined as a directed line in space that
had both magnitude and direction, while a scalar product is defined as the
smallest angle formed between two vectors. Specific vectors are described below
for the left limb only. To determine the range of motion of the carpal joint complex
in degrees, a vector was constructed from the proximal to distal extremity of the
radius (from target 5 to target 6). A second vector was constructed from the distal
extremity of the radius to the distal extremity of the metacarpus (from target 6 to
target 7). Once these vectors were formed the scalar product was determined.
Using the average value calculation, the average maximum flexion that occurred
on the caudal aspect of the carpus during that trial period was determined.

To determine the range of motion of the fetlock joint in degrees, a vector was
constructed from the distal extremity of the radius to the distal extremity of the
metacarpus (target 6 to target 7). A second vector was constructed from the
distal extremity of the metacarpus to the distal aspect of the hoof (target 7 to
target 8). Next, the scalar product and average value were calculated to determine
the average maximum flexion that occurred on the palmar aspect of the fetlock

joint during that trial period.

35

To determine forelimb abduction in degrees, a vector was constructed from the
proximal to distal extremity of the radius (target 5 to target 6). Next a scalar
product was taken between this vector and the Y axis of the reference coordinate
system. Mean value calculation provided the average maximum abduction that
occurred in both forelimbs during that trial period.

Mean values for head and withers excursion were determined from the
sinusoidal progression of targets 1 and 4 respectively, in the Z axis. Head and
withers excursion were coupled with the left and right forelimbs so that excursion
average values represented the average distance, in cm, the head or withers
targets travelled in the positive 2 axis while the sound or lame leg was in its
support phase.

Stance phase was defined as the time period where there was no vertical
displacement of the hoof (target 8). In other words, it was the time associated with
the 2 value of the hoof target when it was between 0 to 3.5 cm in height. Using
the average value calculation, this provided a number which represents the
average time the hoof remained in contact with the ground.

Calculation of stride length involved the sinusoidal progression of hoof target X
trajectories (target 8), using three-dimensional position data. This provided a value
representing the average distance, in cm, the hoof travelled in a caudal to cranial

direction for that time period. The average value was determined as described

above.

D. Statistical Analysis

The effects of intra-articular amphotericin-B on stride length, stance phase,
forelimb abduction, carpal and fetlock range of motion and head and withers
excursion for the sound and the lame limb were analyzed using as two way
analysis of variance (P _<_ 0.05). The Student-Newman-Keuls test was used to
evaluate differences between means.” The subjective effect of amphotericin-B on
lameness was analyzed using the Friedman’s Block Test (P_<_0.05). The Signed

Ranks test was used to evaluate differences between means.”

VI.RESULTS

The average subjective evaluation of forelimb lameness was graded 0/5
(clinically sound horses) during baseline measurements. The mean (X_+_SEM)
subjective lameness grade was significantly increased during all measurement

periods when compared to baseline values (Figure 3).

AAEP Lameness Scale (1 -5)

 

*
*

 

 

 

 

 

Days

Figure 3. The mean (XiSEM) subjective lameness scores as determined
by two independent examiners during baseline measurements (B) and 9,16
and 23 days post induction of arthritis. Examiners used the AAEP lameness
classification scale.” (**=P50.01)

37

38

The pattern of head movement was affected by lameness induction. During
baseline measurements, the head consistently moved in a symmetric sinusoidal
pattern (Horse 1, Figure 4a). The head target was raised and lowered during the
support phase of each forelimb, producing an up and down head movement for
the support phase of each forelimb. There was no significant difference in head
excursion when either forelimb was in its support phase (Figure 11).

However, when the subjective lameness grade was 3/5, the head moved in a
sinusoidal pattern, but lacked symmetry (horse 4, Figure 4b). Similar to baseline
measurements, the head target was raised and lowered during the support phase
of each forelimb, but the amount of head excursion that occurred while the lame
limb was in its support phase was decreased significantly (Figure 11).

When the subjective lameness was 4/5, the upward head excursion that
occurred while the lame leg was in its support phase was completely eliminated
(horse 2, Figure 4c). The head was at its maximum height just prior to the support
phase of the lame limb and dropped throughout the support phase. Then the
head was elevated to its maximum height during the support phase of the sound
limb before weight bearing occurred on the lame limb. This pattern reduced the
frequency of head excursion by 50 percent in the lamest horses (Figure 4a vs 4c).
The pattern of withers target movement mimicked the head target both during

baseline measurements and after the induction of lameness.

185
180
175
170

Head displacement (cm)

(horse 2).

 

 

 

 

 

 

'- t".
A l'- n:
r‘, .51 * ' I
_f 1 - ‘1 ,I

1.! ‘- ."I
i '1. r
1 1,: .

. 1.-

: * s

”i

i

 

“16

 

 

 

fl
:1,
F "
! '1
1" 5 '4 -.
I" 2” II“;
" .- ; t r'.
l 5 '- -‘ l :‘ '1
1' ', 3 ': : z
'1 : ~. : i 1 i
\ 5 i I 3 t '.
-t l '. = i . ‘-
1 = - i ‘ 1
r z '. i I t.
:1 i '. _i . 3
i t' i : 1,
I't g 1 x .
‘- i I . l,
i 1‘ i: r 1
‘z' 1 t
(1

l

 

‘1?
=7

e. "'
--..
m.~....u-...u.~..

V..-

 

 

IRA.
1 2

Time (sec)
— Left Front Hoof ---- Head

Figure 4. Representative verticle displacement (2 component in cm) of the
head (target 1) and left front hoof (target 8) as horses trotted (4 m/s for 6
seconds) on the treadmill. a) Recording of head movement before arthritis
induced (horse 1). b) Recording of head movements post arthritis induction
for a 3/5 subjective lameness grade (horse 4).
movements post arthritis induction for a 4/5 subjective lameness grade

Hoof displacement (cm)

c) Recording of head

40

The mean (X i SEM) values for all variables measured for the sound and lame

limb are listed in Table 6.

Table 6. The effect of amphotericin-B induced arthritis on stride length,
stance phase, carpal and fetlock range of motion, forelimb abduction, head
and withers excursion are listed in the following order: the sound limb then
the lame limb. All values are presented as means (XiSEM).(#=range of

motion, *=p$0.05, **=pgo.01)

MESUREMENT PERIOQ (Dag

 

Variable B 9 16 20
Stride 99.64115 102.71 :1 .7 99.00; 1 .1 1 00.51121
langth 90.543: 1.5 93.91100 95.63133 97.07100
Stance 0.22:0.01 02210.03 0.22:0.00 02210.01
mass 0.21 $0.01 02010.01 0.2111001 02210.01
Forelimb 0.32:1.0 19011.1 17511.4 0.54:1.4
63939” 0.02: 1.0 7.97:0.7 9.15: 1.0 88611.4
Carpal 60.94_+_4.3 58.06125" 02.00;“ 61.79;”
5333'" 68.10138 63.071; 1.9 62.50i2.7 65.40;I-_3.1
Fetlock 07.41395 88.96111 00.01120 00.09127
R.O.M.' 86.24122 72.95345“ 75.11132 76.01 :49
1609M

Head 4.02105 1:079:22 11.1 212.1 " 10.91 1.24"
(Excursion 4.57: 0.02 1.001003" 2.161100" 2.31 _+_0.07"
Withers 5.13.102 7.30:0.7‘ 6.93:0.7' s.95-_r_0.7‘
Excursion 4.77104 2.55_4_-_0.9 01510.0 3.67:0.8

41
The stance phase of the right and left forelimbs was 0.221001 and 0.211001

seconds respectively (X1SEM), with horses trotting at 4m/s on a treadmill.
Lameness induction did not affect stance phase (Figure 5).

Forelimb abduction of the right and left forelimb was 8.32 11.6 and 8.32110
degrees respectively. The intra-articular injection of amphotericin-B did not
significantly affect forelimb abduction (Figure 6).

Baseline measurements of stride length for the right and left forelimbs was
99.641 1.6 and 98.54 11.5, cm respectively (X1SEM) as horses trotted on the
treadmill. Stride length was unaltered by lameness induction (Figure 7).

Carpal range of motion of the right and left forelimbs was 66.94143 and
68.10138 degrees respectively, as horses trotted at 4 m/s. Carpal range of motion
was decreased significantly nine days after the induction of arthritis in the sound
limb (Figure 8), but returned toward baseline values by day 16 after arthritis
induction.

Baseline measurements of fetlock range of motion for the sound and lame
forelimbs was 87.411 2.6 and 86.241 2.2 degrees respectively. Although fetlock
range of motion of the sound limb was not affected significantly by the intra-carpal
injection of amphotericin-B, it was decreased significantly during all measurement
periods in the lame forelimb (Figure 9).

Withers excursion of the right and left forelimbs was 5.131 0.2 and 4.77 10.4

42

cm respectively. Withers excursion was increased significantly during all lameness
measurement periods while the sound limb was in its support phase, and
decreased significantly only at day nine while the lame limb was in its support
phase (Figure 10).

Baseline measurements of head excursion for the right and left forelimb was
4.821 0.5 and 4.571 0.32 cm respectively, while horses trotted on the treadmill at
4 m/s. After lameness induction, head excursion was increased significantly
compared to baseline values during all measurement periods when the sound
forelimb was in its support phase and decreased significantly when the lame

forelimb was in its support phase (Figure 11).

43

Stance Phase (sec)

 

0.3

  

0.2

0.1

 

 

 

 

B\\\\\\\\\\\

 

ISound Limb ELame Limb

Figure 5. Stance phase (X1 SEM in seconds) of the sound forelimb and the
lame forelimb before (B) and 9, 16 and 23 days after lameness induction.

Forelimb Abduction (degrees)

 

12

 

 

 

 

 

 

Days

.Sound Limb BLame Limb

Figure 6. Forelimb abduction (X1SEM in degrees) of the sound forelimb
and the lame forelimb before (B) and 9, 16 and 23 days after lameness
induction.

45

Stride Length (cm)

 

120

100

80

60

4O

20

 

 

 

 

 

0

 

°\\\\\\\\\\\
"’ \\\\\\\ \ \\

_L
N

.Sound Limb IZILame Limb

Figure 7. Stride length (X1SEM in cm) of the sound forelimb and the lame
forelimb before (B) and 9, 16 and 23 days after lameness induction.

46

Carpal Range of Motion (deg)

 

80

60

40

20

 

 

 

 

   

Days

ISound Limb @Lame Limb

Figure 8. Carpal range of motion (X1SEM in degrees) of the sound
forelimb and the lame forelimb before (B) and 9, 16 and 23 days after
lameness induction. (**=pgo.01)

47

Fetlock Range of Motion (deg)

 

100

80

60

40

20

 

 

 

 

 

Days

ISound Limb BLame Limb

Figure 9. Fetlock range of motion (X1SEM in degrees) of the sound
forelimb and the lame forelimb before (B) and 9, 16 and 23 days after
lameness induction. (*=p5 0.05.**=p50.01)

48

Withers Excursion (cm)

 

1O

 

 

 

 

 

 

 

 

 

16

Days

.Sound Limb E Lame Limb

Figure 10. Withers excursion (X1SEM in cm) initiated during the support
phase of the sound forelimb and the lame forelimb before (8) and 9, 16 and
23 days after lameness induction. (* = p_<_0.05)

18
16
14
12
10

49

Head Excursion (cm)

 

 

*
*

 

*
*
.1...

//§ //
B 9 Days 1 6

 

 

 

 

 

 

 

 

cream

 

 

 

 

I Sound Limb B Lame Limb

Figure 11. Head excursion (X1SEM in cm) initiated during the support
phase of the sound forelimb and the lame forelimb before (B) and 9,16 and
23 days after lameness induction. (* =p50.05 **=p$0.01.)

VII. DISCUSSION

The computer-assisted three-dimensional video gait analysis technology used
in human medicine were successfully adapted for locomotion analysis in the horse.
Amphotericin-B was used to induce a unilateral forelimb lameness of two weeks
duration and alterations in the equine trotting gait were determined and compared
to baseline values.

Head movements in the sound and lame horse were determined to be the most
sensitive indicators of lameness (Figure 11). Similar to a sound horse at a walk
87, our horses heads fell and rose in a sinusoidal fashion during the support phase
of each forelimb (Figure 4) while trotting and this fall-rise frequency was reduced
by up to half in the lame horse. In contrast to previous reports,“”” the head fell
during the lame forelimb support phase and rose when the sound diagonal pair
was on the ground.

Withers movements were determined to be the next most sensitive indicator of
lameness. Withers movement closely paralleled head movement, as previously
speculated,” in both the sound and lame trotting horse.

Several theories exist regarding the asymmetric movement of the head and neck
in the lame horse. These include an attempt to reduce the weight supported by
the affected limb,” and an effort to shift the center of gravity caudally, away from

the lame forelimb, as the head is elevated.6 An alternate theory to explain the

50

51

head and neck movements seen in unilateral forelimb lameness might be an
uncoupling of their weight from the lame forelimb as the head and neck experience
a "free fall" like phenomenon. This logically follows, knowing that the head and
neck represent 10 % of body weight,‘51 and that the head and withers were
lowered during the support phase of the lame limb in this project. This theory is
supported by three different quantitative studies which examine the kinetics of
unilateral forelimb lameness using force platforms.°'”'” In these articles, it was
uniformly demonstrated that the injured forelimb of walking or trotting horses have
significame decreased vertical forces and cranio-caudal decelerative horizontal
forces. It was also noticed that horizontal decelerative forces are increased and
horizontal accelerative forces are decreased in the sound forelimb.°'”'” This
theory is also supported by two publications demonstrating that the hip drops
during the support phase of the lame hindlimb.°7'” In this project, withers
excursion decreased when the lame forelimb was on the ground limb, and
movements of the withers and head occurred together. It would seem logical that
the hip and withers would move in a similar manner to compensate for lameness,
therefore providing further support to the "free fall" theory.

Stance phase, defined as the time the limb is in contact with the ground,”
averaged around 220 msec for both the sound and lame limb and was not

significantly affected by the induction of lameness. Similar stance phase times of

52

242 msec were demonstrated in an induced carpal lameness model where a force
platform analysis was used in horses trotting between 2.7 and 2.9 mls.“ In
contrast, published case reports have shown stance phase to both increase“7 and
decrease with lameness.”'”

Though quantitative reports describing the lame horse are uncommon, it has
been demonstrated in 30 sound trotting standardbreds using high-speed
cinematography, that variations in limb movement in any particular horse were very
small.“5 It is theorized that the symmetric nature of animal gait will allow individual
asymmetries to be identified as lameness. It has been suggested that a lame
horse may alter the swing phase of the lame limb to minimize the distressing
aspects of the lameness,6 and therefore affect stride length. Stride length is
defined by convention as the horizontal distance covered in the plane of
progression beginning with the stance phase of one limb and ending with the
subsequent placement of that same limb on the ground.“50 To simplify
calculations in this project, stride length was re-defined as the excursion one limb
makes in the positive X direction, because this value would be exactly half of that
determined conventionally. It is conceivable that the definition for stride length may
change, if future lameness evaluation studies are standardized by using a treadmill.
In our study stride length was not significantly altered by the induction of

lameness. Stashak suggests” that changes in the cranial and caudal phases of

53
stride are the important issue since the length of stride of the affected limb must

remain the same as the contralateral limb if the horse is to travel in a straight line.
A horse with a decreased cranial phase of stride may compensate by increasing
the caudal phase of stride in the same limb and therefore leave the stride length
unaffected. This may have occurred in this project and could be particularly true
on a treadmill but these aspects were not examined. Stride frequency,defined as
the time required to complete one stride,” did not change with the induction of
lameness, since stride length was unaffected and treadmill speed was held
constant at 4 m/s.

Forelimb abduction and carpal range of motion were evaluated because it has
been hypothesized that carpal lameness causes a horse to move with a paddling
or circumducted gait due to the pain flexion induces.” However, in this study
carpal range of motion and forelimb abduction were not consistently significantly
affected in either the sound or lame forelimb during any of the measurement
periods. These findings may have validity only for unilateral forelimb lameness
whereas, the paddling gait may occur with bilateral forelimb lameness.

Fetlock range of motion in the sound limb was not altered by unilateral forelimb
lameness, but a significant decrease in range of motion occurred in the lame limb
during all lameness measurement periods (Figure 9). It is theorized?” and has

been demonstrated in 25 horses at a walk using a force platform, that force

54
compensation is provided by the diagonal hind limb in a unilateal forelimb

lameness, since these limbs are in their support phase at the same time.91
Though right diagonal hind limb movement was not examined in this project, this
diagonal hind limb compensation could explain a normal fetlock range of motion
in the sound limb and significant changes in the lame forelimb fetlock range of
motion.

Amphotericin-B was used to induce arthritis in this project because,although the
inciting cause for DJD is unknown, primary soft tissue inflammation is one of the
proposed theories in horses and has been implicated as the primary cause of
osteoarthritis in man.” Additionally, synovitis is almost always present in cases of
equine degenerative joint disease”"io and the polyene antibioticsn", specifically
amphotericin-b73 have been used successfully to create synovitis in the horse.
Using the dosages described in this project, it provided a synovial arthritis and a
consistent lameness of 2 weeks duration.

Lameness has been defined as a deviation from the normal gait due to pain or
mechanical dysfunction.” One of the deleterious side effects of experimental
arthropathies is discomfort and pain. Pain, defined as the activation of a discrete
set of receptors and neural pathways, are usually aroused by stimuli that are
noxious or damaging to tissues.” The sensitivity of a tissue to pain perception is

directly related to the presence of nociceptors, or pain receptors.” Nociceptors

55

are numerous in the periosteum, joint capsule and tendons. The prostaglandins
released during tissue damage are known to enhance the sensitivity of nociceptors
to pain while cyclo-oxygenase inhibitors, like phenylbutazone, provide analgesia
by inducing a pronounced suppression of the inflammatory response.” When
nociceptor are stimulated by a chemical insult, a nerve impulse is produced and
conducted along the afferent fibers. These afferent fibers enter the spinal cord
from the dorsal root and terminate on dorsal horn neurons. The dorsal horn
contains neurons that can project the nociceptive message to higher brain centers,
relay the message to other cells and inhibitory interneurons that modify the
nociceptive message.” Pain modulation can therefore occur at the nociceptor, the
dorsal root or at higher brain centers.

Phenylbutazone was used once in the protocol as a single oral dose to
modulate the acute inflammatory reaction. It remains a widely used and effective
non-steroidal anti-inflammatory drug (NSAID) for the equine species,” because its
acidic nature potentiates drug accumulation in inflamed tissues.”97 Synovitis is
often reduced by a brief regimen since synovial fluid levels approach 50% of the
plasma concentration.” Phenylbutazone can cause an irreversible antagonism of
the cycIo-oxygenase enzyme for as long as 12 to 24 hours, reduce tissue
prostaglandin (PG) production and thus prevent the sensitization of pain

97,99

receptors. In this project, analgesia was not provided exclusively at the

56

receptor by using phenylbutazone, because our protocol required a synovitis of
two weeks duration.

Opioids activate opioid receptors (agonist), block opioid receptors (antagonist)
or do either (agonist-antagonist) depending on the site they stimulate.‘°° Identified
opioid receptors include the mu, kappa, sigma and delta receptors.‘°° It is known
that opioid analgesics interact at selective endogenous recognition sites and that
a high opioid receptor density exists in the dorsal horn of the spinal cord and
certain subcortical regions of the brain.” The opioid butorphanol tartrate was
used as the primary analgesic in the protocol since opioids can inhibit pain
transmission from primary afferent nociceptors, modulating neurons or directly
affect pain transmission in the spinal cord, brain stem and various parts of the
brain.” Butorphanol tartrate, a synthetic morphinan that is chemically related to
naloxone,‘°1 acts as a competitive antagonist at the mu receptor and an agonist
at the sigma and kappa receptor. It specifically has a high affinity for kappa
receptors which are believed to be of primary importance in analgesia.‘” It is an
effective analgesic, as has been demonstrated in several animal pain model
studies ‘”‘”, and was noted to provide analgesia for cancer pain, post surgery
pain, post surgical cancer pain and prepartum pain.‘” Butorphanol was used to
provide analgesia in this project because it has a rapid onset of action, is centrally

acting so it does not interfere with the inflammatory process of this synovitis model

57

and is efficacious when given intramuscularly.‘”‘” Also, it was easy to use in a
clinical setting since it is not a scheduled drug‘” and has relatively few deleterious
effects.”

The fourth edition of the 1991 American Association of Equine Practitioners
(AAEP) Guide for Judging gf Eguegrian Events contains a subjective lameness
classification scale.” This classification scheme is a commonly used lameness
scale and was used in this project to provide continuity with current practices, to
determine the subjective degree of lameness produced by this model, to ascertain
how subjective and objective lameness evaluation compared and to provide an
example of the arbitrary scales available for lameness evaluation. Both computer
determinations and subjective evaluation of the vertical component of head
movements demonstrated a significant change when compared to baseline values.
In contrast, subjective evaluation perceived head fall to occur while the sound
forelimb was weight bearing and objective evaluation demonstrated head fall to
occur while the lame forelimb was in its support phase. Since subjective
evaluation has been proven unreliable, ”'33 measurement systems which generate
quantitative information are preferred 9 over visual assessment techniques.

Target motion is always an issue when used to improve limb and body segment
identification since these targets are prone to measurement errors due to skin

movement.9'”'3"”. There are concerns that target motion may limit the usefulness

58

”3"”7 since all

of cinematography and videography in assessing joint angles,
automated motion analysis systems require the attachment of markers to the skin.
The body locations selected for targets positions (I’ able 4) were bony landmarks
with minimal soft tissue or muscle coverage to minimize this effect."""”'37 Target
motion errors have been quantified in 6 normal horses at a walk.” It was
demonstrated that target motion perpendicular to the long axis of the limb was
undetectable at all sites measured and that substantial motion of targets parallel
to the long axis of the limb only occurred proximal to the carpus and tarsus. It is
likely that changes in skin marker position are more significant at higher speeds”
and around joints proximal to the carpus,”'” therefore our concerns for target
movement were restricted to the proximal lateral radius (targets 5 and 9, Table 4).
Assuming that quantified target movement occurred only in a proximal distal
direction and not a cranio-caudal direction,” it was inferred that target movement
in this project was in a direction co-linear with the proximal vector and did not
significantly underestimate the calculated angles formed in the carpal joint
complex.

The goal of studying equine joint disease and performing quantitative lameness
evaluation using experimentally induced arthritis is identifying precise diagnostic

criteria for lameness so the site of pain or mechanical dysfunction could be

determined in a clinical setting.” It is recognized, however, that amphotericin-B

59

and other experimental models do not completely reproduce the clinical and
pathological changes seen in naturally occurring equine DJD and are limitations
in the experimental design.”74

Treadmill evaluations have been used extensively for upper respiratory tract
evaluations and, when combined with a videoendoscopic exam, has proven to be
a very safe and useful diagnostic procedure.‘”"” Fredricson et al have
demonstrated the gait reproducability between exercising sessions to be good,
and found a good correlation between the gait repeatability on the track and on
the treadmill."° The treadmill allowed kinematic analysis to occur in a controlled
environment, enabled horses to be assessed indoors under standardized
conditions and form of exercise. The central location of a treadmill facilitated the
positioning of multiple cameras which allowed three-dimensional analysis to be
performed on multiple gait cycles. Hoof visibility was not complicated, as seen on

dirt and track surfaces, due to the less compliant rubber-steel make-up of the

belt.” The treadmill proved to be a safe and useful device for lameness evaluation.

VII. SUMMARY AND CONCLUSIONS
It has been stated that the complex movement of quadrupeds requires skilled
analysis at many levels and that the generated data must be reduced to a simpler

form if rational decisions are to be formed regarding clinical cases?“ Using

60

amphotericin-B to create a unilateral forelimb lameness and a computer work
station with three dimensional software capabilities, the following conclusions were
drawn.

1. The computer-assisted video gait analysis technology used in this project
was successfully adapted from a human laboratory for use in normal and lame
horses.

2. In normal horses, the vertical component of head and withers movement
occurred synchronously and symmetrically in a sinusoidal fashion, during the
support phase of both forelimbs. Using this forelimb lameness model, the head
and withers continued to move synchronously, but the symmetry between sound
and lame forelimbs was no longer present. Head and withers motion, determined
to be the most sensitive variables, were noted to drop during the support phase
of the lame forelimb and rise during the support phase of the sound forelimb.

3. The baseline measurements for forelimb abduction and stance phase for the
sound forelimb, the lame forelimb and the sound to lame forelimb ratio were not
significantly different from any of the measurement periods. These variables were
concluded to be unreliable for the assessment of equine carpal lameness.

4. Measurement of stride length was significantly different from baseline values
when assessing the sound to lame forelimb ratio at day nine only. Carpal range

of motion was significantly different from baseline values when assessing the

61

sound forelimb at day nine only. These variables were concluded to be unreliable
for the assessment of equine carpal lameness.

5. Fetlock range of motion in the lame forelimb and sound to lame forelimb
ratio; withers excursion when the lame limb is in its support phase and head
excursion for the sound, lame and the sound to lame forelimb ratio were
significantly different from baseline values during all measurement periods and

were concluded to be reliable in the assessment of equine carpal lameness.

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