The effect of the interosseous ligament and selected antebrachiocarpal ligaments on rotation of the radius during extension of the carpus.

OBJECTIVE: To evaluate the effect of the interosseous ligament and selected antebrachiocarpal ligaments on the internal rotation of the radius relative to the ulna, during carpal extension. STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Twenty-four cadaveric canine forelimbs. METHODS: Twenty-four forelimbs were disarticulated at the elbow joint and the antebrachia were prepared for testing. The forelimbs were divided to 6 groups, defined by the order in which ligaments were transected. All specimens were tested intact and after transecting each of the ligaments with the order defined by the group. Rotation of the radius relative to the ulna, caused by extension of the carpus, was measured using a sensor connected to the radius. RESULTS: The mean(±sd) maximum internal rotation of the radius (5.94° ± (1.23°)) with all the ligaments intact was significantly greater (p < 0.012) than the mean(±sd) maximum internal rotation of the radius (3.13° (± 1.13°)) after transecting the interosseus ligament. Transecting the interosseous ligament subsequent to one of the other ligaments caused a decrease in internal radial rotation (p = 0.629), while, transecting the short radial collateral ligament caused an increase in radial rotation (p = 0.629). Transecting the palmar radiocarpal and ulnocarpal ligaments had no effect on radial rotation. CONCLUSION: The interosseous ligament was stretched with internal rotation of the radius due to carpal extension. Carpal flexion resulted in external rotation of the radius. This effect was lost when the interosseus ligament was transected. CLINICAL SIGNIFICANCE: Rotation of the radius is associated with carpal extension, and is likely an intrinsic part of forelimb biomechanics.

Use of bilateral superficial gluteal muscle flaps for the repair of ventral perineal hernia in dogs: A cadaveric study and short case series.

OBJECTIVE: To describe bilateral mobilization of the superficial gluteal muscle (SGM) to treat ventral perineal hernias in dogs. STUDY DESIGN: Cadaveric study and short case series. SAMPLE POPULATION: Male dog cadavers (n = 10) weighing between 5 and 42 kg and three dogs treated for ventral perineal hernia. METHODS: Cadavers were positioned in right and left lateral recumbency to free the origin and insertion of the ipsilateral SGM except for muscle fibers originating on the first tail vertebra and sacrotuberous ligament. The dogs were placed in ventral recumbency to approach the perineum and rotate the muscle flaps. The insertions of the SGM were sutured together ventral to the anal sphincter muscle. The dorsal border of the overlapping tendons was sutured to the anal sphincter muscle, and the ventral border was sutured to the ischiourethralis muscle. The amount of overlap between bilateral flaps was measured. The SGM flaps were used to revise recurrent perineal hernias in three dogs. RESULTS: Superficial gluteal muscle flaps were created without damage to the blood supply in all dogs. The overlap between the bilateral flaps ventral to the anal sphincter measured 0 to 2.4 cm. No recurrence was detected at follow-up (6-12 months) in the three dogs treated with these flaps. CONCLUSION: Superficial gluteal muscle flaps were mobilized without damage to the blood supply and crossed the midline ventral to the anal sphincter. Flaps were used successfully to repair ventral perineal hernias in three dogs. CLINICAL SIGNIFICANCE: Bilateral SGM flaps can be considered to repair ventral perineal hernias.

The effect of extension and loading of the carpus on radial rotation.

OBJECTIVE: To describe the direction and magnitude of the rotation of the radius relative to the ulna during extension of the carpus and to describe the effect of carpal extension on internal and external rotation of the radius relative to the ulna. STUDY DESIGN: In vitro experiment. ANIMALS: Cadaveric canine thoracic limbs (n = 11). METHODS: Eleven thoracic limbs were collected from 6 healthy mixed breed dogs of medium build. Each specimen was radiographed to ensure that the carpal and elbow joints were free of pathology. The elbow joint was disarticulated and the distal thoracic limb was prepared for biomechanical testing. Each specimen was stripped of soft tissue, leaving the soft tissues around the proximal aspect of the radius and ulna intact. The interosseous ligament, pronator teres muscle, and all the soft tissues distal to the distal metaphysis of the radius were also left intact. In the 1st part of the study, the rotation of the radius relative to the ulna was measured while extending the carpal joint using a system of weights and pulleys attached to the manus. In the 2nd part of the study, the internal and external rotation of the radius relative to the ulna was performed by applying an internal and external rotational load to the radius using a system of weights and pulleys attached to the radius. The internal and external rotation of the radius was measured with the carpus unloaded and with the carpus extended by applying a load of 5 kg to the manus. RESULTS: Extension of the carpus resulted in internal rotation of the radius relative to the ulna. With the carpus extended under a maximum load of 2 kg, the mean (± SD) internal rotation of the radius was 4.3 ± 2.1° for all specimens. With the carpus unloaded, the mean internal and external rotation of the radius was 11.5 ± 2.9° and 22.5 ± 7.7° for all specimens, respectively. With the carpus loaded (extended under 5 kg load), the mean internal and external rotation of the radius was 3.3 ± 1.2° and 7.3 ± 2.0° for all specimens, respectively. The difference between internal and external rotation with the carpus loaded and unloaded was significant. CONCLUSION: Extending the carpus results in internal rotation, and proximal translation of the radius relative to the ulna. Loading the carpus in extension decreases the internal and external rotation of the radius relative to the ulna. A better understanding of the interaction between the carpus and the elbow may improve our understanding of the pathogenesis of elbow dysplasia.