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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)

Full access
in American Journal of Veterinary Research

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)

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of toe grabs, exercise intensity, and distance traveled as risk factors for subclinical to mild suspensory apparatus injury (SMSAI) in Thoroughbred racehorses and to compare incidence of severe musculoskeletal injury (MSI) in horses with and without SMSAI.

Design—Nested case-control study.

Animals—219 Thoroughbred racehorses racing or in race training.

Procedure—Racehorses were examined weekly for 90 days to determine incidence of suspensory ligament injury and monitor horseshoe characteristics. Every horse's exercise speeds and distances were recorded daily. Conditional logistic regression was used to compare exposure variables between incident case (n = 25) and selected control (125) horses. Survival analysis was used to compare time to MSI for horses with (n = 41) and without (76) SMSAI.

Results—The best-fitting logistic model for the data included age (< 5 vs ≥ 5 years old), toe grab height the week of injury (none vs very low, low, regular, or Quarter Horse height), and weekly distance the week preceding injury (miles). Although the 95% confidence intervals for all odds ratios included 1, the odds for SMSAI appeared to increase with the presence of a toe grab, higher weekly distance, and age ≥ 5 years. Horses that had SMSAI were significantly more likely to have a severe MSI or severe suspensory apparatus injury than were horses that did not.

Conclusions and Clinical Relevance—Results suggest that pre-existing SMSAI is associated with development of severe MSI and severe suspensory apparatus injury. Modifying training intensity and toe grab height for horses with SMSAI may decrease the incidence of severe MSI. (J Am Vet Med Assoc 2001; 218:1136–1144)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To compare the strength of the sutured linea alba, in vitro, using 2 suture patterns.

Animals

12 clinically normal llamas.

Procedure

2 incisions in the linea alba of 12 llamas were closed with a simple continuous or inverted cruciate pattern, and tissue was harvested after 10 days. In 6 llamas, the simple continuous line was intact; the inverted cruciate specimens contained 6 sutures. In 6 llamas, 1 knot was excised in the simple continuous pattern to simulate a failed line; the cruciate pattern contained 5 knots. Tissue sections were taken from cranial, between, and caudal to the linea alba incisions to compare fascial thickness. The sutured specimens were mounted in a mechanical testing system and tested to failure. A mixed-model ANOVA was used to evaluate the effects of suture pattern and incisional position on mechanical properties.

Results

Significant differences were not found between suture patterns or between location for yield force, failure force, or yield strain, whereas failure strain was lower for the intact simple continuous pattern than the inverted cruciate pattern (P = 0.003). From histomorphometric analysis, the caudal tissue specimens were significantly thinner than the middle tissue specimen cranial to the umbilicus (P = 0.006).

Conclusion

There was no significant difference in monotonic breaking strength of the linea alba sutured with the simple continuous or inverted cruciate pattern.

Clinical Relevance

These results justify the use of the simple continuous pattern over the cruciate pattern for ventral midline closure in llamas because of the ease of placement and speed. (Am J Vet Res 1996;57:938–942)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To provide an accurate and detailed description of the laparoscopic anatomy of the abdomen of horses positioned in dorsal recumbency and to compare those observations with laparoscopic anatomy of standing horses. The effects of laparoscopy and positional changes on arterial blood pressure and blood gas values also were investigated.

Design

Descriptive anatomic study.

Sample Population

Laparoscopy was performed on 6 horses (2 mares, 2 geldings, and 2 stallions) to record the normal laparoscopic anatomy of the abdomen in dorsal recumbency.

Procedure

Feed was withheld from all horses for 36 hours. Horses, under general anesthesia, were examined in horizontal and inclined positions (head-up and head-down). Intermittent positive-pressure ventilation was used, arterial blood pressure was continuously monitored, and samples for arterial blood gas measurements were taken at intervals.

Results

The main structures of diagnostic relevance observed in the caudal region of the abdomen were the urinary bladder, mesorchium and ductus deferens (left and right), left and right vaginal rings, insertion of the pre-pubic tendon, random segments of jejunum and descending colon, pelvic flexure of the ascending colon, body of the cecum, and cecocolic fold. The main structures observed in the cranial region of the abdomen were ventral surface of the diaphragm, falciform ligament and round ligaments of the liver, ventral portion of the left lateral, left medial, quadrate, and right lateral lobes of the liver, spleen, right and left ventral colons, sternal flexure of the ascending colon, apex of the cecum, and stomach.

Conclusions

Alterations in cardiovascular and respiratory function in response to pneumoperitoneum and various positional changes indicated the need for continuous and throrough anesthetic monitoring and support. Comparison of anatomic observations made in dorsally recumbent, inclined horses with those reported for standing horses should enable practitioners to make patient positioning decisions that best suit access to specific visceral structures. Development of special instrumentation for manipulation of the viscera in horses, particularly the intestinal tract, would increase the diagnostic and therapeutic capabilities of laparoscopy during dorsal recumbency. (Am J Vet Res 1996;57:923–931)

Free access
in American Journal of Veterinary Research

Objective

To determine anatomic landmarks for a lateral approach for arthrocentesis of the proximopalmarolateral aspect of the distal interphalangeal (DIP) joint in horses and the likelihood of entering synovial structures other than the DIP joint through this approach.

Design

Prospective study.

Sample Population

Paired forelimbs of 8 cadavers and 12 horses.

Procedure

Anatomic preparations were used to determine anatomic landmarks. Positive-contrast arthrography was used to determine which structures were entered.

Results

Landmarks for the lateral approach included a depression in the proximal border of the lateral ungular cartilage and the palmar border of the middle phalanx. Use of the lateral approach for arthrography resulted in deposition of contrast material exclusively in the DIP joint in only 13 of 20 limbs, whereas use of the dorsal approach resulted in deposition of contrast material exclusively in the DIP joint in 20 of 20 limbs.

Clinical Implications

The lateral approach is an alternative to the conventional dorsal approach to the DIP joint in horses; however, inadvertent entry into adjacent synovial structures is a possible complication. The lateral approach provides an additional portal for through-and-through lavage and arthroscopic access to the palmar aspect of the DIP joint. (J Am Vet Med Assoc 1998;212:1413–1418)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine the effect of surgical technique and use of a rigid centralizing device on stem positioning and geometric reconstruction in the sagittal plane during total hip replacement in dogs.

Sample Population

Bilateral femurs from 8 adult mixed-breed canine cadavers.

Procedure

Femurs were prepared for femoral stem implantation, using 4 variations in technique. Proximal femoral reconstruction and femoral stem positioning were evaluated on radiographs.

Results

Implants evaluated in this study accurately reconstructed displacement of the femoral head of the intact canine femur in the sagittal plane. Centralization of the distal aspect of the stem was optimized by use of an undersized femoral stem. Ostectomy at the level of the lesser trochanter resulted in the smallest diaphysis-to-implant angle. Anteversion and retroversion of implants significantly decreased the distance between the distal tip of the implant and the adjacent cortex, compared with normoversion. The centralizing device significantly increased the minimum distance between the distal tip of the implant and adjacent cortex but did not improve the odds of actually centralizing the tip of the implant.

Conclusions and Clinical Relevance

Malpositioning of implants in the sagittal plane may be minimized through ostectomy at the lesser trochanter and use of an undersized implant positioned in normoversion. Use of a polymethylmethacrylate centralizing device will help eliminate contact between the implant tip and adjacent cortex. Implantation of an undersized femoral component, avoidance of substantial anteversion or retroversion, and use of a rigid centralizing device are recommended when using the prosthesis described-for total hip replacement of dogs. (Am J Vet Res 1999;60:1126–1135)

Free access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To compare the torsional mechanical properties of 2 external skeletal fixators (ESFs) placed with 2 intramedullary pin (IP) and transfixation pin (TP) size combinations in a model of raptor tibiotarsal bone fracture.

SAMPLE

24 ESF-synthetic tibiotarsal bone model (polyoxymethylene) constructs.

PROCEDURES

Synthetic bone models were fabricated with an 8-mm (simulated fracture) gap. Four types of ESF-synthetic bone model constructs (6/group) were tested: a FESSA with a 1.6-mm IP and 1.6-mm TPs, a FESSA with a 2.0-mm IP and 1.1-mm TPs, an acrylic connecting bar with a 1.6-mm IP and 1.6-mm TPs, and an acrylic connecting bar with a 2.0-mm IP and 1.1-mm TPs. Models were rotated in torsion (5°/s) to failure or the machine angle limit (80°). Mechanical variables at yield and at failure were determined from load deformation curves. Effects of overall construct type, connecting bar type, and IP and TP size combination on mechanical properties were assessed with mixed-model ANOVAs.

RESULTS

Both FESSA constructs had significantly greater median stiffness and median torque at yield than both acrylic bar constructs; FESSA constructs with a 1.6-mm IP and 1.6-mm TPs had greatest stiffness of all tested constructs and lowest gap strain at yield. No FESSA constructs failed during testing; 7 of 12 acrylic bar constructs failed by fracture of the connecting bar at the interface with a TP.

CONCLUSIONS AND CLINICAL RELEVANCE

Although acrylic bar ESFs have been successfully used in avian patients, the FESSA constructs in this study were mechanically superior to acrylic bar constructs, with greatest benefit resulting from use with the larger TP configuration.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine morphological and mechanical properties of trabecular bone of horses with a bone fragility syndrome (BFS; including silicate-associated osteoporosis).

Sample—Cylindrical trabecular bone samples from the distal aspects of cadaveric third metacarpal bones of 39 horses (19 horses with a BFS [BFS bone samples] and 20 horses without a BFS [control bone samples]).

Procedures—Bone samples were imaged via micro-CT for determination of bone volume fraction; apparent and mean mineralized bone densities; and trabecular number, thickness, and separation. Bone samples were compressed to failure for determination of apparent elastic modulus and stresses, strains, and strain energy densities for yield, ultimate, and failure loads. Effects of BFS and age of horses on variables were determined.

Results—BFS bone samples had 25% lower bone volume fraction, 28% lower apparent density, 18% lower trabecular number and thickness, and 16% greater trabecular separation versus control bone samples. The BFS bone samples had 22% lower apparent modulus and 32% to 33% lower stresses, 10% to 18% lower strains, and 41 % to 52% lower strain energy densities at yield, ultimate, and failure loads, compared with control bone samples. Differences between groups of bone samples were not detected for mean mineral density and trabecular anisotropy.

Conclusions and Clinical Relevance—Results suggested that horses with a BFS had osteopenia and compromised trabecular bone function, consistent with bone deformation and pathological fractures that develop in affected horses. Effects of this BFS may be systemic, and bones other than those that are clinically affected had changes in morphological and mechanical properties.

Full access
in American Journal of Veterinary Research