CT evaluation of elbow congruity in dogs: radial incisure versus apical medial coronoid process fragmentation.

OBJECTIVES: To compare elbow congruity in two cohorts of Labrador retrievers affected with either radial incisure or apex fragmentation of the medial coronoid process. MATERIALS AND METHODS: Dogs were included if they had elbow lameness and a CT diagnosis of a fissure or fragmentation of the medial coronoid process occurring either along the radial incisure or at the coronoid apex. Radioulnar joint space was measured incrementally from the lateral to the medial coronoid process on transverse slice images. Axial radioulnar congruency was also measured at the apex and mid-coronoid in the dorsal plane and at the base of the coronoid in the sagittal plane. RESULTS: We studied 99 elbows (in 66 dogs) of which 56 had a fissure or fragmentation along the radial incisure and 43 had an apical fragment. No difference was found between the two groups at the different measuring points - with the exception of a transverse plane radioulnar joint space measurement in the radial incisure group that was smaller adjacent to the lateral coronoid process. CLINICAL SIGNIFICANCE: Abnormal ulnar morphology in the radial incisure group could result in a fulcrum effect within the radioulnar joint, overloading the radial incisure and predisposing to osteochondral damage at this site.