Magnetic Resonance Imaging in Osteochondritis Dissecans of the Humeral Capitellum: Preoperative Assessment of Lesion Size and Lateral Wall Integrity.

Purpose Magnetic resonance imaging (MRI) is a helpful tool in the evaluation of osteochondritis dissecans (OCD) of the humeral capitellum. The relationship between MRI appearance and clinically relevant intraoperative findings is incompletely understood. The goal of this study was to evaluate capitellar OCD lesions via preoperative MRI and to determine its accuracy in predicting lesion characteristics including lesion size and capitellar lateral wall integrity. Methods Patients surgically treated for capitellar OCD between January 2010 and June 2018 were reviewed. Preoperative MRI images were assessed by a musculoskeletal radiologist with documentation of lesion size, location, violation of the lateral wall, and stage, in accordance with previously established criteria. These data were compared with intraoperative findings. Involvement of the lateral wall of the capitellum was defined using 2 methods: (1) subchondral edema or articular cartilage disruption in the lateral third of the capitellum (lateral third method) or (2) disruption of the proximal-distal subchondral line along the lateral border of the capitellum descending vertically before the subchondral bone turns horizontally to form the radiocapitellar articulation (capitellar lateral wall sign method). Diagnostic test characteristics were compared for both methods. Results We reviewed the preoperative MRIs of 33 elbows with capitellar OCD and found no significant difference in mean lesion size between preoperative MRI (1.12 cm2) and intraoperative measurement (1.08 cm2). For detection of lateral wall integrity, preoperative MRI evaluation using the capitellar lateral wall sign method had an accuracy of 93%, sensitivity of 80%, specificity of 96%, positive predictive value of 80%, and negative predictive value of 96%. Conclusions Preoperative MRI is a valid predictor of lesion size. The capitellar lateral wall sign method is highly accurate in the identification of lateral wall involvement, which may influence preoperative planning. Type of study/level of evidence Diagnosis II.