Introduction. Osteochondritis dissecans (OCD) is a localised disorder of subchondral bone and the overlying articular cartilage. The most commonly used classification systems involve arthroscopy and MRI. Aim. To investigate the correlation between arthroscopic and MR findings in patients with OCD of the talus. Methods. 16 ankles in 14 patients with radiographically proven OCD were reviewed. Nine were male and five female. Mean age was 35yrs (range 18–64yrs). The lesions were staged independently using the Guhl. 1. arthroscopic and Dipaola. 2. MR classification systems. Results. Arthroscopically there were eight stable and eight unstable lesions. Of the eight stable lesions, MRI staged five as stable and three as unstable. Of the eight unstable lesions, MRI staged six as unstable and two as stable. This gives a sensitivity of diagnosing unstable lesions as 0.75, with a specificity of 0.63. Conclusions. This small study demonstrates that MR scans may have some limitations in classifying OCD lesions of the talus. Possible explanations are discussed. We propose that MRI findings, of OCD of the talus, should not be taken in isolation, but correlated with the patients symptoms and signs to avoid unnecessary arthroscopy

Purpose: Osteochondritis dissecans (OCD) of the capitellum most commonly affects adolescent pitchers and gymnasts, and presents with pain and mechanical symptoms. Fragment excision is the most commonly employed surgical treatment; however, patients with larger lesions have been reported to have poorer outcomes. It’s not clear whether this is due to increased contact pressures on the surrounding articular surface, or if fragment excision causes instability of the elbow. The purpose of this study was to determine if fragment excision of simulated OCD lesions of the capitellum alters kinematics and stability of the elbow. Method: Nine fresh-frozen cadaveric arms were mounted in an upper extremity joint motion simulator, with cables attaching the tendons of the major muscle tendons to motors and pneumatic actuators. Electromagnetic receivers attached to the radius and ulna enabled quantification of the kinematics of both bones with respect to the humerus. Three-dimensional CT scans were used to plan lesions of 12.5% (mean 0.8cm2), 25%, 37.5%, 50%, and 100% (mean 6.2cm2) of the capitellar surface, which were marked on the capitellum using navigation. Lesions were created by burring through cartilage and subchondral bone. The arms were subjected to active and passive flexion in both the vertical and valgus-loaded positions, and passive forearm rotation in the vertical position. Results: No significant differences in varus-valgus or rotational ulnohumeral kinematics were found between any of the simulated OCD lesions and the elbows with an intact articulation with active and passive flexion, regardless of forearm rotation and the orientation of the arm (p> 0.7). Radiocapitellar kinematics were not significantly affected during passive forearm rotation with the arm in the vertical position (p=0.07–0.6). Conclusion: In this in-vitro biomechanical study even large simulated OCD lesions of the capitellum did not alter the kinematics or laxity of the elbow at either the radiocapitellar or ulnohumeral joints. These data suggest that excision of capitellar fragments not amenable to fixation can be considered without altering elbow kinematics or decreasing stability. Further study is required to examine other factors, such as altered contact stresses on the remaining articulation, that are thought to contribute to poorer outcomes in patients with larger lesions