MRI Analysis for Clarification of Mechanism of Ankle Osteoarthritis

Abstract

Category: Ankle Arthritis Introduction/Purpose: We have previously studied the relationship between Takakura–Tanaka classification stages and bone-marrow edema (BME) in order to elucidate the pathology of ankle osteoarthritis (ankle OA) on magnetic resonance imaging (MRI). Moreover, we have investigated that BME onset on the talocrural joint can be predicted according to radiographic findings. In the present study, we focused on the changes around the subtalar joint to examine the relationship between talar lateral process impingement (TLPI) and foot and ankle joint alignment, and whether TLPI can be predicted on the basis of X-ray findings. Methods: We assessed 30 feet of 30 patients who had a diagnosis of ankle OA in our hospital and underwent MRI. Alignment was assessed radiographically by measuring the tibial anterior surface angle (TAS), the tibial lateral surface angle (TLS), the lateral talo-first metatarsal angle (LTMT), the lateral talocalcaneal angle (LTC), and the tibial axis–talar ratio (T-T ratio). MRI was obtained with the talocrural, subtalar and Chopart joints into 22 subdivided areas to examine the frequency of BME for each patient. TLPI was considered positive (+) when BME was found in the talar lateral process. The patients were divided into two groups according to TLPI positivity or negativity. Their BME frequency was examined, and significant differences in radiographically measured values were analysed with a t-test. Results: In the TLPI (+) group, BME development occurred at significantly higher frequencies in all areas except those surrounding the lateral process (p = 0.002). In addition, TLS was significantly lower (p = 0.02), and LTMT was significantly higher (p = 0.04). When the cut-off value on the ROC curve was set at TLS of =74° and LTMT of =19°, TLPI onset could be predicted with a sensitivity of 75% and a specificity of 71%. Conclusion: Our results revealed that in the TLPI (+) group, progression of the anteriorly opened talocrural joint and talar dorsiflexion may be causing the talar lateral process to hit the calcaneus. Furthermore, in the TLPI (+) group, BME in other areas also occurred at higher frequencies, and symptoms around the ankle joints may be occurring at multiple locations. The fact that TLPI could be predicted from radiography findings suggests that this may be a potential predictive tool of the severity of clinical symptoms.