Frequency and Coexistence of Ununited Anconeal Process with Other Primary Elbow Dysplasia in Dogs

Ununited anconeal process (UAP) is one of the four primary causes of elbow dysplasia (ED). Radiography (X-ray) and computed tomography (CT) are commonly employed imaging techniques for the diagnosis of elbow dysplasia. The objective of this retrospective study was to evaluate the frequency and distribution of UAP in dogs referred for elbow imaging and to analyze the coexistence of this disorder with other primary causes of ED, such as medial coronoid process disease (MCPD), osteochondritis dissecans (OCD), and joint incongruity (IC).

The study population comprised 108 dogs of both sexes, aged between 3 and 15 months, of breeds predisposed to ED: 69 German Shepherds, 23 Labrador Retrievers, and 16 Golden Retrievers. All dogs underwent both radiographic and CT examinations of the elbow joints. Categorical data were analyzed using Fisher's exact test to evaluate breed-related findings and lesion coexistence, with significance set at 5%. Inter-method reliability was assessed using Cohen's kappa coefficient (ĸ).

Based on radiographic and CT findings, elbow dysplasia was diagnosed in 53 dogs and 58 dogs, respectively. UAP was identified in 9 cases and only in German Shepherds. Among the 9 UAP-positive dogs, coexistence with other ED lesions (most commonly medial coronoid process disease and joint incongruity) was observed in 8 cases. For specific UAP detection, both imaging modalities demonstrated perfect diagnostic agreement (ĸ = 1.0).

UAP was the rarest diagnosed primary etiology of elbow dysplasia in the study population. This disorder has been found only in German Shepherds; however, this observation should be interpreted with reservation due to the unequal breed distribution within the study population. Radiography and computed tomography demonstrated equivalent diagnostic agreement for UAP identification; this result should also be interpreted cautiously due to the limitation of the small number of identified cases of this disorder. Furthermore, UAP occurred more frequently as a concomitant lesion-most commonly in association with medial coronoid process disease and joint incongruity-rather than as a solitary finding.