Comparison of Arthroscopic, X-ray and MRI T2 Mapping Findings for Varus Ankle Osteoarthritis

CATEGORY: Ankle Arthritis; Arthroscopy INTRODUCTION/PURPOSE: We have previously reported the indication criteria for supramalleolar osteotomy for varus ankle osteoarthritis using our arthroscopic classification. However arthroscopy is invasive, MRI T2 mapping (T2M) is also useful for noninvasive preoperative assessment of articular cartilage condition. The purpose of this study is to investigate the relationship among these. METHODS: The subjects were 19 patients with 19 joints, 3 males and 16 females, mean age 65.2 years (45-78), 3 joints in stage 2, 8 joints in stage 3a, and 8 joints in stage 3b according to radiographic classification by Takakura et al. Measurements were taken on the coronal section of the talar dome. To evaluate the arthroscopic findings, we used our five grades classification, which is based on the percentage of eburnation areas on the articular surface, we measured the percentage of the area of the missing joint space to the width of the talar dome in X-rays and the ratio of the area of cartilage signal loss to the width of the talar dome in T2M. We determined how well the radiographic and T2M findings match the arthroscopic findings. RESULTS: The results showed that there were 2 joints in grade 2, 15 joints in grade 3, and 2 joints in grade 4 in arthroscopic classification. The concordance rate between arthroscopy and X-rays measurements was 100% (2 joints/2 joints) for grade 2, 46.7% (7/15) for grade 3, and 0% (0/2) for grade 4. In all 10 unmatched joints, X-rays underestimated the condition of the articular cartilage compared to arthroscopic findings. The concordance rate between arthroscopy and T2M measurements was 50% (1/2) for grade 2, 80% (12/15) for grade 3, and 100% (2/2) for grade 4. Two joints were underestimated and two were overestimated by T2M compared to the arthroscopic findings. CONCLUSION: Compared to arthroscopic findings, X-rays tended to underestimate the condition of articular cartilage, while T2M tended to overestimate it, but in general, T2M showed a higher concordance rate with the arthroscopic findings than X-rays. T2M is more useful than X-rays as a tool for cartilage evaluation to determine the operative method for varus ankle osteoarthritis.