Search Results

Abstract

Objective—To determine effects of incremental radial shortening and subsequent ulnar ostectomies on joint surface contact patterns in a canine elbow joint model.

Sample Population—Paired forelimbs from 9 adult dogs.

Procedure—Joint casting was performed by placement of colored polymethylmethacrylate in the elbow joint cavity and loading in a materials testing system at physiologic angle and load. Joint casting was performed in unaltered specimens, after radial shortening, and after subsequent distal ulnar ostectomy, proximal ulnar ostectomy, and proximal ulnar ostectomy with intramedullary pinning. Computer-aided analysis of photographs of proximal radial and ulnar articular surfaces without joint casts was performed before and after each casting procedure.

Results—All increments of radial shortening changed the size and location of radial and ulnar contact areas. The radial contact area became smaller, the anconeal contact area disappeared, the medial coronoid contact area migrated craniolaterally, and the lateral projection of the coronoid process became a contact area. A proximal ulnar ostectomy stabilized with an intramedullary pin restored normal contact area size and location and restored continuity of the radial and coronoid contact areas across the radioulnar articulation in 6 of 10 specimens. A midshaft ulnar ostectomy, distal to the level of the radioulnar ligament, had no effect on contact patterns. A proximal ulnar ostectomy without stabilization resulted in varus deformity during loading.

Conclusion and Clinical Relevance—Proximal radial shortening, which creates articular step incongruity, changes the location and size of the radioulnar contact areas. Dynamically stabilized ulnar ostectomies proximal to the radioulnar ligament restore contact patterns in vitro . (Am J Vet Res 2001;62:1548–1556)

Abstract

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: 721–728)

Abstract

Objective—To develop a model for measuring rotary stability of the canine elbow joint and to evaluate the relative contribution of the anconeal process (AN), lateral collateral ligament (LCL), and medial collateral ligament (MCL).

Sample Population—18 forelimbs from 12 canine cadavers.

Procedure—Forelimbs were allocated to 3 experimental groups (6 forelimbs/group). Each intact forelimb was placed in extension at an angle of 135° and cycled 50 times from –16° (pronation) to +28° (supination) in a continuous manner at 2.0 Hz. Cycling was repeated following sectioning of the structure of interest (group 1, AN; group 2, LCL; and group 3, MCL). Torque at –12° (pronation) and +18° (supination) was measured for each intact and experimentally sectioned limb. A Student t test was performed to compare torque values obtained from intact verses experimentally sectioned limbs and for comparison with established criteria for differentiation of primary (≥ 33%), secondary (10 to 33%), and tertiary rotational stabilizers (< 10%).

Results—In pronation, the AN was the only primary stabilizer (65%). For supination, the LCL was a primary stabilizer (48%), AN was a secondary stabilizer (24%), and MCL was a tertiary stabilizer (7%).

Conclusions and Clinical Relevance—With the elbow joint in extension at an angle of 135°, the AN is a primary rotational stabilizer in pronation, and the LCL is a primary stabilizer in supination. Disruption of the AN or LCL may affect rotary range of motion or compromise stability of the elbow joint in dogs. (Am J Vet Res 2002;63:1520–1526)

Abstract

Objective—To determine the effect of sliding and wedge osteotomies of the humerus on the joint surface contact areas in anatomically normal elbow joints of dogs.

Sample Population—Left thoracic limbs from 5 skeletally mature mixed-breed canine cadavers.

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)

Abstract

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)

Abstract

Objective—To determine the distribution of force between the articular surfaces of the humerus and radius and between the humerus and ulna in normal canine forelimbs.

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)

Abstract

Objective—To compare activities of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and matrix metalloproteinase (MMP)-3 and contents of sulfated glycosaminoglycan (S-GAG) in joint fluid obtained from dogs with hip dysplasia (HD) and clinically normal dogs, evaluate correlations among these markers in joint fluid obtained from dogs with HD, and evaluate correlations between each marker and clinical and radiographic variables.

Animals—26 dogs with HD (clinical group) and 43 clinically normal Beagles (control group).

Procedure—Joint fluid was aseptically collected from the hip joints of all dogs. For each dog in the clinical group, age, duration of lameness, radiographic osteoarthritis (OA) score, and Norberg angle in each affected joint were recorded. Activities of IL-1β, IL-6, TNF-α, and MMP-3 and S-GAG contents were measured. Values were compared between groups by use of Mann-Whitney U tests, and the Spearman rank correlation test was used to evaluate correlations among markers and between each marker and clinical or radiographic variables.

Results—Values of all markers were significantly higher for the clinical group, compared with values for the control group. There was a moderate positive correlation between lameness duration and IL-6 activity and a strong negative correlation between the Norberg angle and IL-1β activity.

Conclusions and Clinical Relevance—Analysis of our results indicated that there was a significant increase in markers of OA in dogs with HD. Activities of IL-1β and IL-6 in joint fluid of dogs with HD may be influenced by the severity of laxity in the hip joint and lameness duration, respectively. (Am J Vet Res 2005;66:2028–2033)

Abstract

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 pin placement.

Sample Population—Cervical portions (C3 through C6 vertebrae) of 14 cadaveric canine vertebral columns.

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)

Abstract

Abstract

Objective—To compare radiographic and arthroscopic abnormalities in juvenile dogs with clinically apparent hip dysplasia.

Design—Case series.

Animals—52 dogs (70 hip joints) with clinical signs of hip dysplasia scheduled to undergo triple pelvic osteotomy.

Procedure—A ventrodorsal radiographic projection of the pelvis was evaluated by a radiologist unaware of clinical and arthroscopic findings, and radiographic osteoarthritic abnormalities were judged and scored as absent (0), mild (1), moderate (2), or severe (3). Arthroscopy was performed by a surgeon unaware of clinical and radiographic findings, and arthroscopic abnormalities were graded from 0 (normal) to 5 (exposed, eburnated subchondral bone).

Results—In 30 of the 70 (43%) hip joints, no radiographic osteoarthritic abnormalities were seen. Severe, full-thickness articular cartilage lesions (grade 4) of the femoral head or acetabulum were seen arthroscopically in 14 (20%) joints. Lesions ≥ grade 2 were seen in 60 (86%) joints. Partial tearing of the ligament of the femoral head was present in 57 (81%) joints, and complete rupture was seen in 5 (7%). Radiographic abnormalities were seen in 13 of the 14 (93%; 95% confidence interval, 66% to 99.8%) joints with grade 4 arthroscopic abnormalities but in only 23 of the 46 (50%; 95% confidence interval, 35% to 65%) joints with grade 2 or 3 arthroscopic abnormalities.

Conclusions and Clinical Relevance—Results suggest that radiography is not a sensitive method for identifying moderate cartilage lesions in juvenile dogs with hip dysplasia. If moderate cartilage lesions are an important prognostic indicator for the success of triple pelvic osteotomy, then methods other than radiography should be used to detect these lesions. (J Am Vet Med Assoc 2005;227:1091–1094)