Preoperative Imaging Criteria for Unstable Osteochondritis Dissecans of the Capitellum

The stability of an osteochondritis dissecans (OCD) lesion of the humeral capitellum may be determined by intraoperative probing with unstable lesions being displaceable. Although preoperative imaging is used to diagnose and determine treatment of these lesions, it is unclear whether unstable lesions on imaging correspond to those found intraoperatively. We therefore examined the concordance between preoperative imaging and intraoperative instability and examined the imaging features of the patients who healed without surgery. We retrospectively reviewed 61 patients who underwent OCD of the humeral capitellum surgery or nonoperative treatment. All patients had plain radiography, MRI, and/or CT scans. The presence or absence of stability was determined intraoperatively by the International Cartilage Repair Society OCD classification. We determined the sensitivity, specificity, and predictive value of various imaging findings to predict instability. The following preoperative imaging features were associated with intraoperative instability: a displaced fragment, epiphyseal closure of the capitellum, or a lateral epicondyle observed on radiographs; irregular contours of the articular surface or a high signal interface on T2-weighted MRI; and a displaced fragment observed on CT. Unstable lesions were more common when the epiphysis of the capitellum was closed. Intralesional segmentation was sensitive for detecting an unstable lesion, whereas displaced type on the radiographs and displaced fragment on the CT were specific. The following imaging findings were not seen in nonoperative patients: displaced type and closure of the epiphyseal line on radiographs, irregular contours of the articular surface, articular defects, and T2 high signal intensity interface between the fragments and their bed on the MRI or a displaced fragment on the CT. Although we found high sensitivity for some preoperative findings on imaging, none reached 100% of sensitivity. Preoperative MRI related to the intraoperative assessment of stability. Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.