Abstract: Objectives: To quantify net joint moments, joint powers, and joint reaction forces
(JRF) across the hock, stifle, and hip joints in Labrador Retrievers with and
without cranial cruciate ligament (CCL) disease. To investigate differences in joint
mechanics between normal, CCL deficient, and contralateral pelvic limbs.
Study Design: Cross-sectional clinical study.
Animals: Clinically normal (n=14) and CCL-deficient (n=9) Labrador Retrievers.
Methods: Each limb was analyzed separately and classified as normal, CCLdeficient
or sound contralateral limb. Kinematic, ground reaction force (GRF),
and morphometric data were combined in an inverse dynamic approach to
compute hock, stifle and hip net moments, powers and JRF, while trotting.
Results: Vertical and braking GRF and JRF were significantly decreased in CCLdeficient
limbs. In affected limbs, extensor moments at the hock and hip, flexor
moment at the stifle and power in all 3 joints were less than normal. Kinetics also
identified a greater joint moment and power of the contralateral limbs compared
with normal, particularly of the stifle extensor muscles group.
Conclusion: Lameness resulting from CCL disease affected predominantly reaction
forces during the braking phase and the extension during push-off. A greater
contribution of the contralateral limbs to propel the dog forward was identified.
Clinical Relevance: Reductions in joint motion, loads, and muscle contraction
were interpreted as modifications adopted to reduce or avoid painful mobilization
of the injured stifle joint. The increased joint moment and power of the contralateral
compensating side may correlate with the lameness observed, but also with
the predisposition of contralateral limbs to CCL deficiency in dogs.
Abstract: Objective: To identify morphometric characteristics of the pelvic limb musculature
associated with the development of cranial cruciate ligament (CCL) deficiency
in Labrador Retrievers.
Study Design: Cross-sectional clinical study.
Animals: Pure-bred female (n=18) and male (n=12) Labrador Retrievers with
(n=16) and without (n=14) CCL deficiency.
Methods: Muscle conformation of pelvic limbs was evaluated by physical examination,
radiography (widths of quadriceps, hamstring, and gastrocnemius were expressed
relative to tibial length and to each other), and dual-energy X-ray
absorptiometry (DEXA, lean contents of quadriceps, hamstring, and gastrocnemius
were expressed relative to tibial length and to each other). Pelvic limbs of dogs without
CCL deficiency were classified as normal (n=28 limbs), whereas those with CCL
deficiency were considered diseased (n=18 limbs) or sound contralateral to CCL
deficiency (n=10 limbs). Variables were compared between groups using mixed
models analysis of variance, with Po.05 considered significant.
Results: The ratios of quadriceps width to tibial length (P=.008), hamstring
width (P=.013), and gastrocnemius width (P=.005) on lateral radiographs were
lower in diseased limbs than controls. The mass of hamstring muscles in CCL deficient
limbs was similar to that of normal limbs. The ratio of the lean content of
gastrocnemius to hamstring muscles was greater in diseased (P=.007) and sound
contralateral (P=.013) limbs than in normal limbs.
Conclusions: Atrophy associated with CCL deficiency may predominantly affect
the quadriceps muscle. Dominance of the gastrocnemius muscle over active restraints
to the cranial tibial thrust may be associated with predisposition to CCL
deficiency in Labrador Retrievers.
Clinical Relevance: If confirmed, this dynamic imbalance between muscle groups
of the rear limbs could serve as a basis for screening programs and preventive
rehabilitation.
Abstract: Objective—To evaluate skeletal characteristics of pelvic limbs with and without cranial cruciate
ligament (CCL) deficiency in Labrador Retrievers.
Animals—30 adult purebred Labrador Retrievers.
Procedures—Pelvic limbs (n = 28) of 14 dogs without CCL deficiency were classified as
control limbs, whereas the limbs of 16 dogs with CCL deficiency were considered affected
by (18 limbs) or predisposed to (10 contralateral limbs of dogs with 1 affected limb) CCL deficiency.
Skeletal characteristics were evaluated via physical examination, radiography, and
computed tomography. Radiographic and computed tomographic variables were compared
among limb groups by use of a mixed-model ANOVA.
Results—The tibial plateau slope was steeper in CCL-deficient limbs but not in predisposed
limbs, compared with the slope in control limbs. The angle between diaphyseal and proximal
tibial axes was increased in both CCL-deficient and predisposed limbs. The relative
width of the proximal portion of the tibia and the inclination of the patellar ligament did not
differ among limb groups. The overall and distal femoral anteversion angles were greater in
CCL-deficient and predisposed limbs, whereas the femoral condyle trochanteric angle was
decreased in those limb groups, compared with findings in control limbs.
Conclusions and Clinical Relevance—Cranial angulation of the proximal portion of the
tibia, excessive steepness of the tibial plateau, and distal femoral torsion appeared more
likely to be associated with CCL deficiency than femoral angulation, tibial torsion, intercondylar
notch stenosis, and increased inclination of the patellar ligament.
Abstract: Objective—To determine mass, center of mass (COM), and moment of inertia (ie, body
segment parameters [BSPs]) of hind limb segments by use of a noninvasive method based
on computerized tomography (CT) in Labrador Retrievers with and without cranial cruciate
ligament (CCL) disease and to provide regression equations to estimate BSPs of normal,
CCL-deficient, and contralateral hind limbs.
Animals—14 clinically normal and 10 CCL-deficient Labrador Retrievers.
Procedures—Bone, muscle, and fat areas were identified via CT. Mass, COM, and moment
of inertia were determined on the basis of tissue densities in the thigh, crus, and foot segments.
Regression models were developed to determine predictive equations to estimate
BSP on the basis of simple morphometric measurements.
Results—The thigh and crus of CCL-deficient limbs weighed less than in contralateral segments.
Thighs weighed less in CCL-deficient than in normal limbs. The thigh moment of
inertia was less in CCL-deficient than in contralateral limbs. The crural COM was located
more distally in normal limbs, compared with other limbs. Predictive equations to estimate
BSP varied by parameter, body segment, and limb status.
Conclusions and Clinical Relevance—BSPs of the thigh and crus varied with segment
and status of the hind limb in Labrador Retrievers with or without CCL disease. Equations
to estimate BSP on the basis of simple morphometric measurements were proposed,
providing a basis for nonterminal studies of inverse dynamics of the hind limbs in Labrador
Retrievers. This approach may offer new strategies to investigate the pathogenesis of
nontraumatic joint diseases.
Abstract: Objectives—To evaluate the contribution of proximodistal alignment of the patella to patellar
luxation, and to evaluate the structures contributing to proximodistal alignment of the patella
relative to the femoral trochlea.
Study Design—Retrospective study using a convenience sample.
Animals—Medium to giant breed dogs (n¼106).
Methods—Medical records and stifle radiographs of 106 dogs were reviewed. Radiographic measurements
evaluated the proximodistal alignment of the patella with respect to the femoral trochlea,
distal aspect of the femur, and proximal aspect of the tibia. Measurements were compared between
dogs with clinically normal stifles (controls; n¼51 dogs, 66 stifles), and dogs with a clinical diagnosis
of medial patellar luxation (MPL, n¼46 dogs, 65 stifles) or lateral patellar luxation (LPL,
n¼9 dogs, 11 stifles) using ANOVA.
Results—In dogs with MPL, the ratio of patellar ligament length (PLL) to patellar length (PL) was
increased, as was the ratio of the distance from the proximal aspect of the patella to the femoral
condyle (A) to PL (Po.0001). Dogs with LPL had a decreased A:PL (P¼.003) and an increased
ratio of the proximal tibial length (PTL) to distal tibial width (DTW; P¼.009).
Conclusions—MPL is associated with a relatively long patellar ligament and patella alta in medium
to giant breed dogs. LPL is associated with a relatively long proximal tibia and patella baja. Values
for PLL:PL42.06 and A:PL42.03 are suggestive of the presence of patella alta, whereas a value for
A:PLo1.92 is suggestive of patella baja.
Clinical Relevance—Measurements of both PLL:PL and A:PL are recommended in dogs with
patellar luxation, and surgical correction should be considered in those with abnormal values.
