Computed Tomographic Features of Incomplete Ossification of the Canine Humeral Condyle

Objectives- To describe computed tomographic (CT) features of canine elbows with incomplete ossification of the humeral condyle (IOHC) and investigate co-existing incongruence in the elbow joint. Study Design- Case control study. Animals- Dogs with IOHC (n=20; 38 elbows) and 25 normal elbows. Methods- Elbows with IOHC and normal elbows were assessed by CT. Standardized dorsal and sagittal reconstructions were created at 3 levels using image analysis software to obtain single measurements of the humero-radial and humero-ulnar joint spaces. On dorsal plane reconstructions, joint space measurements were obtained at the center point of the humero-radial and humero-ulnar articulations. Joint incongruity was defined as the difference between the humero-radial and the humero-ulnar joint spaces. Results- Nineteen dogs (95%), all Spaniel breeds, had either bilateral IOHC demonstrable as a saw-toothed intercondylar complete or incomplete hypoattenuating defect with hyperattenuating margins, or IOHC with contralateral humeral condylar fracture (HCF). Joint incongruity values for IOHC were compared with those of normal elbows. Significant differences were noted at the levels of the medial coronoid apex (P<.0001) and base (P<.004) indicative of humero-ulnar incongruence. Evidence of medial coronoid disease in 10 elbows (26%) and degenerative joint disease in 30 elbows (79%) was also found. Conclusions- Presence of elbow incongruence may be an underlying factor in failure of ossification centers to fuse leading to IOHC. Clinical Relevance- IOHC is clearly defined by CT, and it should be considered in larger Spaniel breeds, with a chronic forelimb lameness or HCF.