A comparison of arthroscopic and MRI findings in staging of osteochondral lesions of the talus.

The purpose of the present study was to evaluate the accuracy of MRI compared with arthroscopy in staging of osteochondral lesions of the talus (OLTs). The authors prospectively investigated 50 patients (52 cases) who had undergone both MRI and ankle arthroscopy for OLTs. The 30 males (32 ankles) and 20 females (20 ankles) had an average age of 43 years (range 19-64 years). The correlations between MRI and arthroscopic stagings were also investigated. Preoperative MRI resulted in 7 stage I, 11 stage II, 25 stage III, and 9 stage IV lesions, and ankle arthroscopic findings in 3 stage I, 5 stage II, 35 stage III, and 9 stage IV lesions. No stage V lesion was encountered. A comparison of MRI and arthroscopic stagings revealed that MRI had an accuracy of 81% (42 of 52) for staging of OLTs. MRI correctly staged 3 of 7 stage I lesions, 5 of 11 stage II, 25 of 25 stage III, and 9 of 9 stage IV lesions. Ten mismatched cases were of arthroscopic stage III lesions, which MRI classified as four stage I lesions and six stage II lesions. Thus, MRI staging tended to understate lesion severity. We re-reviewed the ten MR images of the mismatching cases to identify reasons for these mismatches, and subchondral edema was found in six cases. The authors conclude that MRI has accuracy of 81% in staging of OLTs, however, MRI had some limitation in correct staging isolated cartilage lesions of OLTs, especially combined with subchondral edema.