Clinical value of talocalcaneal coalition on MRI

Objective: To analyze the MRI manifestations and classifications of talocalcaneal coalition and to explore its clinical value. Methods: MRI manifestations of 25 cases of talocalcaneal coalition confirmed by operation and pathology from April 2011 to April 2013 were reviewed retrospectively in this study. There were 22 males and 3 females, mean age was 33.76±13.12 years. Thirteen cases had left side of talocalcaneal coalition, and 12 cases had right side of talocalcaneal coalition. Direct and secondary MRI signs of talocalcaneal coalition were analyzed. Talocalcaneal coalitions were classified according to location and morphology on coronal images. Results: Among direct MRI signs, there was 1 case of osseous coalition (4%) demonstrating continued bone marrow across middle talocalcaneal joint; fourteen cases of fibrous coalition (56%) and 10 cases of cartilaginous coalition (40%) demonstrating narrowed joint space and irregularity of the bone interface. Fibrous coalition demonstrated low-signal intensity on T₁-weighted, T₂-weighted and fat-suppressed sequences across the affected joint; cartilaginous coalition demonstrated intermediate signal on T₁WI and intermediate to hyperintensity on T₂WI and fat-suppressed sequence. Among secondary MRI signs, there were 20 cases of bone marrow edema adjacent to the coalition (80%); nine cases of the 'drunken waiter sign' (36%); three cases of 'talar beak sign' (12%); two cases of 'humpback calcaneal sign' (8%); one case of fractures in talocalcaneal coalition (4%). Locational types: seven cases of middle facet talocalcaneal coalition (28%), four cases of posterior facet talocalcaneal coalition (16%), fourteen cases of extra-articular type (56%), and 5 cases of anterior facet talocalcaneal coalition (20%) combined with the other part of talocalcaneal coalition. Morphological types: type Ⅰ: fourteen cases (56%), type Ⅱ: three cases (12%), typeⅢ: seven cases (28%), and type Ⅳ: one case (4%). Conclusion: MRI can clearly demonstrate histologic subtypes, location and morphology of talocalcaneal coalition, providing valuable diagnostic information for clinicians. (authors)