MRI Classification of subtalar and talonavicular joint osteoarthritis

Category: Hindfoot Introduction/Purpose: The sublatar joint is formed by the articulation of the talus and the calcaneus. The Calcaneus had three facets; posterior, middle and anterior that articulate with the talus. The anterior facet is also continuous with the Talonavicular joint. Plain radiography of the foot and ankle is the usual method to detect degeneration in these joints, however plain films do not permit full characterisation of non-ossified structures, such as articular cartilage, marrow tissue and synovial fluid. MRI is a better way to detect these changes. The aim of this study was to develop a quantitative way to score arthritic changes to the subtalar and talonavicular joints using MRI that was usable, repeatable and reliable. Methods: The MRI scans of thirty consecutive subjects with foot and ankle pain were retrospectively evaluated. MRI images were obtained using 1.5-T MRI. Images were interpreted independently by three musculoskeletal radiologists. In order to determine intra-observer reliability as well as the inter-observer reliability two of the readers independently scored the studies twice, more than 14 days apart. Five features of osteoarthritis were scored in the Subtalar joint and the Talonavicular joint. These were; cartilage morphology, subarticular marrow, subarticular cyst, marginal osteophytes and synovitis. The Subtalar joint was scored in eight different regions and Talonavicular joint in two The maximum score for both regions was 100. Scores were summarised and Inter- and Intra-observer agreement was calculated. Intraclass coefficient values less than 0.40 were poor, fair between 0.40 and 0.59 were fair, values between 0.60 and 0.74 were good, and values between 0.75 and 1 excellent. Results: For the 30 MRI scans the mean score for the Subtalar joint ranged from 11.7 to 14.4 and for the Talonavicular joint ranged from 3.7 to 5.6. The inter-observer correlation for the Subtalar joint between the three readers ranged between 0.53 and 0.83 for the individual features but overall was excellent at 0.76. For the Talonavicular joint the total correlation was good at 0.67. The inter-observer ICC for the total score was 0.75 which showed excellent agreement between the three readers. The total intra-observer correlation was excellent. Conclusion: We have designed a novel scoring system subtalar and talonavicular arthritis that is easy to perform and demonstrates excellent reliability and may be an extremely useful tool for clinical trials on ankle arthritis and other studies to diagnose and monitor disease progression