Radiographic evaluation of osteotomized ulnar segments following arthroscopic treatment for canine medial coronoid disease.

Objective: To assess movement of ulnar segments radiographically, following proximal and midshaft ulnar osteotomy or ostectomy after arthroscopic treatment for dogs diagnosed with medial coronoid disease.

Methods: Fragmentation and cartilage wear were treated arthroscopically and the presence of incongruity confirmed. Osteotomies were performed at the mid-point or proximal third of the length of the ulna. The distance of separation between the ulnar segments and the adjacent radius were measured and followed by serial radiographs postoperatively until healing had occurred.

Results: Proximal oblique osteotomies located at one-third the length of the ulna were associated with the most movement of the ulnar segments, most notably of the proximal segment. Osteotomies or ostectomies performed in the middle demonstrated less segmental movement and on average, slightly longer time to heal. Movement of the ulnar segments in both groups occurred immediately, and then peaked at two to four weeks postoperatively, tending to plateau thereafter.

Clinical Significance: Radioulnar incongruity is considered a facet of the aetiopathogenesis of canine medial coronoid disease. This creates abnormal loads and focal wear along the medial coronoid process. Performing an oblique osteotomy at a location measured at the proximal third of the length of the ulna allows increased movement of the proximal segment, which may result in unloading of the medial compartment. Performing an osteotomy or ostectomy distally dampens segmental movement due to constraint of the interosseous ligament. These findings suggest that a proximal oblique osteotomy at this location creates immediate favourable movement with low morbidity.