Correlation Between Histopathology, Arthroscopic and MRI Findings in Medial Coronoid Disease in Dogs

Introduction
Despite recent advances in our understanding of medial coronoid disease (MCD), detailed descriptions of MRI findings in MCD are scarce, The long-term goal of our research is to develop an objective scoring scheme for diagnosing and staging MCD using MRI. As a first step towards this goal, we undertook a systematic comparison of the MRI, arthroscopic and histopathologic findings in dogs with MCD of differing severities.

Materials and Methods
Osteochondral specimens from 25 affected dogs and 5 unaffected controls were evaluated by MRI (using a novel grading scheme), arthroscopy (using a modified Outerbridge scheme) and histopathology.

Results
Modified Outerbridge scores of II and III were observed most commonly. MRI findings and Outerbridge scoring were consistent. On MRI, bone marrow lesions were described as focal in 68% of the cases, with 3 different patterns observed. The most common histopathologic findings were subchondral microfractures, subchondral microfractures continuous with cartilaginous fissures, moderate to severe hypercellularity of the marrow space, trabecular bone necrosis and degenerate articular cartilage. When compared to the controls, there was a reduction in subchondral bone density in affected dogs.

Discussion/conclusions
Although qualitative at this stage, the findings from this study highlight the potential divergence between cartilage lesion score, MRI findings and histopathology. Objective quantitative assessment of subchondral bone quality and quantity may be needed to more completely describe the extent and severity of MCD disease in dogs.