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Comparison of Arthroscopic and Magnetic Resonance Imaging Findings in Osteochondral Lesions of the Talus

Background: Magnetic resonance imaging (MRI) is widely used for diagnosing osteochondral lesions in the talus. The purpose of this study was to directly compare the MRI with the arthroscopic findings. Materials and Methods: MR images of 42 ankles were retrospectively reviewed during a period of 67 months. The osteochondral lesions were evaluated by both MRI (0, normal; 1, subchondral trabecular compression and marrow edema; 2A, subchondral cyst; 2B incomplete separation fragment; 3, unattached, nondisplaced fragment with synovial fluid surrounding it; 4, displaced fragment) and arthroscopy (A, smooth and intact, but soft and ballottable cartilage; B, rough surfaces; C, fibrillations or fissures; D, flap present or bone exposed; E, loose, undisplaced fragment; F, displaced fragment). Arthroscopic grade A was considered to be equivalent to MR grade 1, B and C to MR grade 2A, D to 2B, E to 3, and F to 4. Results: Of the 44 lesions in 42 ankles, 29 lesions marked the same grade on both MRI and arthroscopy (65.9%). Nine lesions were upgraded on arthroscopy (20.5%), and six were downgraded (13.6%). MR grade 3 lesions showed the best correlation (83.3%) and MR grade 1 and 2B lesions showed the worst (50.0 and 55.6 %). Arthroscopic grade A and F showed good correlation (80 and 100%). Grade C and E showed poor (25.0%) and intermediate correlation (66.7%), respectively. Conclusion: The MRI grading of osteochondral lesions in the talus was useful and showed a fairly good correlation with arthroscopic classification. Level of Evidence: IV, Retrospective Case Series