Objective—To compare in vitro mechanical properties
of toggle pins and toggle rods used as suture
anchors and of 3 suture materials (50-lb monofilament
polybutester, No. 5 braided polyester, and 5-mm
woven polyester) commonly used as prosthetic ligaments
in the repair of hip joint luxation in dogs.
Sample Population—Femoropelvic specimens from
the cadavers of 18 dogs.
Procedure—Suture anchors were compared by use
of pullout tests. Suture materials were compared by
use of monotonic and cyclic tensile tests; cyclic tensile
tests were performed with the suture placed over
the edge of an aluminum bar to simulate the edge of
the femoral bone tunnel. In vitro mechanical properties
of the ligament of the femoral head were determined
by use of monotonic tensile tests, using boneligament-bone cadaveric specimens. The in vitro
mechanical properties of the acetabulum-ligamentfemur
complex and of this complex following rupture
of the ligament and stabilization with a toggle rod and
5-mm woven polyester were determined by use of
compression tests that simulated weight-bearing.
Results—Mechanical properties of the toggle rod
were not significantly different from those of the toggle
pin. Woven polyester had the longest fatigue life
in cyclic testing. Hip joints stabilized with a toggle rod
and woven polyester had less than half the strength
in vitro of intact joints.
Conclusions and Clinical Relevance—Results suggested
that a toggle rod or toggle pin can be used for
stabilization of hip joint luxations in dogs. Of the
materials tested, braided polyester had the best in
vitro mechanical properties. (Am J Vet Res 2001;62:
Objective—To assess concurrently the effects of
moderate ligamentous suspensory apparatus injury
(MLSAI), racing-speed exercise, and horseshoe characteristics
on risk of catastrophic suspensory apparatus
failure (SAF) or metacarpal condylar fracture (CDY)
in forelimbs of racehorses.
Sample population—Cadavers of 301 Thoroughbred
racehorses (108 with SAF, 33 with CDY, and 160 control
Procedure—A cross-sectional epidemiologic study
was used to describe distributions and relationships
between MLSAI, exercise, and horseshoe variables.
Logistic regression was used to assess potential risk
factors for developing SAF and CDY.
Results—Exercise variables were more highly associated
with age than height of a steel bar affixed to the
ground surface of the front of a horseshoe (ie, toe
grab) or sex. Marginal associations were detected
between MLSAI and age and height of toe grab.
Higher risk for developing SAF was associated with
MLSAI, use of a pad on a horseshoe, longer interval
since last period of ≥ 60 days without a race or timed
workout (ie, layup), 2 to 5 career races, and higher
intensity of recent exercise. Higher risk for developing
CDY was associated with MLSAI, male horses, age
between 2 and 5 years, higher intensity of recent
exercise, and longer interval since layup.
Conclusions and Clinical Relevance—Recognition
of MLSAI and rehabilitation of affected horses should
reduce incidence of SAF and CDY. Horses in long-term
continuous training with recent high-intensity
exercise are at greater risk for injury. Use of pads in
horseshoes was associated with SAF, although the
relationship may not be causal. (Am J Vet Res 2004;65:1508–1517).
Objective—To assess the accuracy and reliability of a
visual method of evaluating horseshoe characteristics.
Animals—1,199 Thoroughbred racehorses.
Procedure—Characteristics of 1 forelimb horseshoe
were visually assessed on horses immediately
prior to racing by 5 field observers at 5 major
racetracks in California. Characteristics evaluated
included horseshoe type; toe grab height; and the
presence of a rim, pad, and heel traction devices.
Sensitivity and specificity for observer assessment
of horseshoe characteristics were calculated by
comparing observer assessments to a postmortem
laboratory standard for horses that died within 48
hours of a race. Intraobserver agreement was
assessed in a subset of horses by comparing horseshoe
observations made before and after the
horse's race. Interobserver agreement was evaluated
by comparing horseshoe assessment among
observers who examined the same subset of horses
prior to racing on select days.
Results—The sensitivity and specificity of this visual
method of evaluating horseshoe characteristics were
good and ranged from 0.75 to 1 and 0.67 to 1, respectively.
Agreement beyond chance (weighted kappa
values) between observers and the laboratory standard
for toe grab height was fair (0.60 to 0.62).
Intraobserver and interobserver agreements (kappa
values) were high (0.86 to 0.99 and 0.71 to 1, respectively).
Conclusions and Clinical Relevance—Visual observation
of horseshoes can be a feasible and reproducible
method for assessing horseshoe characteristics
prospectively in a large cohort of horses under
racing conditions. (Am J Vet Res 2004;65:1674–1679)
Procedure—Joint casting was performed by placement
of colored polymethylmethacrylate in the elbow
joint cavity followed by loading in a materials testing
system at physiologic angle and load. Joint casting
was performed in unaltered specimens, after 10°
medial opening wedge osteotomy, and after lateral
sliding osteotomy of the proximal portion of the
humerus. Computer-aided analysis of photographs of
proximal radial and ulnar articular surfaces after each
casting procedure was performed.
Results—The lateral sliding humeral osteotomy and
10° medial opening wedge osteotomy significantly
altered joint surface contact regions of the canine
elbow joint. Osteotomies resulted in a reduction in
the size of the radial, ulnar, and combined radioulnar
contact areas. Both osteotomies also resulted in craniolateral
migration of the radial contact area and craniomedial
recession of the ulnar contact area. Although
the reduction in ulnar contact area with these treatments
is consistent with our hypotheses, the reduction
in radial contact area was not anticipated.
Conclusions and Clinical Relevance—Humeral
osteotomies alter joint surface contact areas of the
canine elbow joint in vitro. Humeral osteotomies may
decrease contact areas on the diseased region of the
joint in dogs with elbow dysplasia; however, the overall
decrease in joint surface contact area suggests
that these procedures may induce focal increases in
pressure that may cause iatrogenic cartilage damage
when applied in vivo. (Am J Vet Res 2003;64:506–511)
Objective—To calculate normative joint angle, intersegmental
forces, moment of force, and mechanical
power at elbow, antebrachiocarpal, and metacarpophalangeal
joints of dogs at a walk.
Animals—6 clinically normal mixed-breed dogs.
Procedure—Kinetic data were collected via a force
platform, and kinematic data were collected from
forelimbs by use of 3-dimensional videography.
Length, location of the center of mass, total mass,
and mass moment of inertia about the center of mass
were determined for each of 4 segments of the forelimb.
Kinematic data and inertial properties were combined
with vertical and craniocaudal ground reaction
forces to calculate sagittal plane forces and moments
across joints of interest throughout stance phase.
Mechanical power was calculated as the product of
net joint moment and the angular velocity. Joint
angles were calculated directly from kinematic data.
Results—All joint intersegmental forces were similar
to ground reaction forces, with a decrease in magnitude
the more proximal the location of each joint.
Flexor moments were observed at metacarpophalangeal
and antebrachiocarpal joints, and extensor
moments were observed at elbow and shoulder
joints, which provided a net extensor support
moment for the forelimb. Typical profiles of work
existed for each joint.
Conclusions and Clinical Relevance—For clinically
normal dogs of a similar size at a walk, inverse
dynamic calculation of intersegmental forces,
moments of force, and mechanical power for forelimb
joints yielded values of consistent patterns and magnitudes.
These values may be used for comparison in
evaluations of gait in other studies and in treatment of
dogs with forelimb musculoskeletal disease. (Am J Vet Res 2003;64:609–617)
Objective—To investigate the biomechanics of cervical
vertebral motion units (VMUs) before and after a
ventral slot procedure and after subsequent pin-polymethylmethacrylate
(pin-PMMA) fixation and to
assess the use of smooth and positive-profile threaded
(PPT) pins in pin-PMMA fixation and intravertebral
Sample Population—Cervical portions (C3 through
C6 vertebrae) of 14 cadaveric canine vertebral
Procedure—Flexion and extension bending moments
were applied to specimens before and after creation
of a ventral slot across the C4-C5 intervertebral space
and after subsequent smooth or PPT pin-PMMA fixation
at that site. Data for the C3-C4, C4-C5, and C5-C6
VMUs were compared among treatments and
between pin types, and pin protrusion was compared
between pin types.
Results—Compared with values in intact specimens,
ventral slot treatment increased neutral zone range of
motion (NZ-ROM) by 98% at the treated VMUs and
appeared to decrease overall ROM at adjacent VMUs;
pin-PMMA fixation decreased NZ-ROM by 92% at the
treated VMUs and increased overall NZ-ROM by 19%
to 24% at adjacent VMUs. Specimens fixed with PPT
pins were 82% (flexion) and 80% (extension) stiffer
than smooth–pin-fixed specimens. Overall, 41% of
pins protruded into foramina; PPT pins were more
likely to protrude into transverse foramina.
Conclusions and Clinical Relevance—Results indicated
that fixation of a cervical VMU alters the biomechanics
of adjacent VMUs and may contribute to
degeneration of adjacent intervertebral disks. Use of
threaded pins may lower the incidence of pin loosening
and implant failure but enhances the likelihood of
transverse foramina penetration. ( Am J Vet Res 2005;66:678–687)
Objective—To compare macrostructural and microstructural features of proximal sesamoid bones (PSBs) from horses with and without PSB midbody fracture to gain insight into the pathogenesis of PSB fracture.
Sample Population—PSBs from 16 Thoroughbred racehorses (8 with and 8 without a PSB midbody fracture).
Procedures—Parasagittal sections of fractured and contralateral intact PSBs from horses with a PSB fracture and an intact PSB from age- and sex-matched control horses without a PSB fracture were evaluated for visual, radiographic, microradiographic, histologic, and his-tomorphometric differences in bone porosity, vascular channels, heme pigment, trabecular anisotropy, and pathological findings.
Results—Fractured PSBs and their contralateral intact PSBs had more compacted trabecular bone than did control PSBs. Focal repair or remodeling was evident in the palmar aspect of many fractured and contralateral intact PSBs. Fracture coincided with microstructural features and propagated from the flexor to the articular surface.
Conclusions and Clinical Relevance—Fractured PSBs had adapted to high loading but had focal evidence of excessive remodeling and porosity that likely predisposed the horses to complete fracture and catastrophic injury. Detection of focal injury before complete fracture provides an opportunity for prevention of catastrophic injury. Development of diagnostic imaging methods to assess porosity of PSBs may help to identify at-risk horses and allow for modifications of training and racing schedules to reduce the incidence of PSB fracture in Thoroughbred racehorses.
To assess the motion of the proximal sesamoid bones (PSBs) relative to the third metacarpal bone (MC3) of equine forelimbs during physiologic midstance loads.
8 musculoskeletally normal forelimbs (7 right and 1 left) from 8 adult equine cadavers.
Each forelimb was harvested at the mid-radius level and mounted in a material testing system so the hoof could be moved in a dorsal direction while the radius and MC3 remained vertical. The PSBs were instrumented with 2 linear variable differential transformers to record movement between the 2 bones. The limb was sequentially loaded at a displacement rate of 5 mm/s from 500 N to each of 4 loads (1.8 [standing], 3.6 [walking], 4.5 [trotting], and 10.5 [galloping] kN), held at the designated load for 30 seconds while lateromedial radiographs were obtained, and then unloaded back to 500 N. The position of the PSBs relative to the transverse ridge of the MC3 condyle and angle of the metacarpophalangeal (fetlock) joint were measured on each radiograph.
The distal edge of the PSBs moved distal to the transverse ridge of the MC3 condyle at 10.5 kN (gallop) but not at lower loads. The palmar surfaces of the PSBs rotated away from each other during fetlock joint extension, and the amount of rotation increased with load.
CONCLUSIONS AND CLINICAL RELEVANCE
At loads consistent with a high-speed gallop, PSB translations may create an articular incongruity and abnormal bone stress distribution that contribute to focal subchondral bone lesions and PSB fracture in racehorses.
Objective—To describe forelimb horseshoe characteristics
of horses racing on dirt surfaces and determine
whether these characteristics vary with region
of California, season, horse characteristics, and race-related
Animals—5,730 Thoroughbred racehorses.
Procedure—From June 17, 2000, to June 16, 2001,
the characteristics of 1 forelimb horseshoe of horses
that raced on dirt surfaces at 5 major racetracks in
California were recorded. These characteristics included
shoe type; toe grab height; and presence of a rim,
pad, and heel traction devices (jar caulks, heel stickers,
heel blocks, and special nails). Horse and race
information was obtained from commercial records.
One race/horse was randomly selected.
Results—99% of forelimb horseshoes were aluminum
racing plates, 35% had a pad, 23% had a rim,
and 8% had a heel traction device. A toe grab was
observed on 75% of forelimb horseshoes (14% very
low [≤ 2 mm], 30% low [> 2 and ≤ 4 mm], 30% regular
[> 4 and ≤ 6 mm], and 1% high [> 6 and ≤ 8 mm]).
Forelimb horseshoe characteristics varied with region
of California, season, age and sex of the horse, race
purse and distance, and track surface condition. Loglinear
modeling revealed that all of these factors were
Conclusions and Clinical Relevance—Complex
interrelationships among forelimb horseshoe characteristics
and region, season, age and sex of the horse,
and race-related factors need to be considered when
evaluating the relationships between injury and
horseshoe characteristics in Thoroughbred racehorses.
( Am J Vet Res 2004;65:1021–1030)
Objective—To determine the distribution of force
between the articular surfaces of the humerus and
radius and between the humerus and ulna in normal
Sample population—12 cadaveric canine right forelimbs.
Procedure—Transarticular force maps were created
by placing a tactile array pressure sensor into the
elbow joint cavity and loading cadaveric forelimbs in a
materials testing system. Mean joint forces were
determined at loads of 50, 100, 150, and 200 N.
Results—All tests produced 2 distinct areas of high
load that corresponded with the proximal articular surfaces
of the radius and ulna. Mean forces for the radial
proximal articular surface were slightly but significantly
greater than for the ulna, averaging 51% to
52% of total force for all applied loads.
Conclusions and Clinical Relevance—The proximal
articular surface of the ulna contributes substantially
to load transfer through the canine elbow joint.
Abnormalities, which increase this load, might contribute
to canine elbow joint dysplasia, specifically
fragmentation of the medial coronoid process and
osteochondritis dissecans of the medial aspect of the
humeral condyle. In the treatment of these conditions,
the normal force distribution within the canine
elbow joint should be taken into consideration. (Am J Vet Res 2005;66:132–135)