Incidence and clinical relevance of tibiofibular synostosis in fractures of the ankle which have been treated surgically.

Abstract

In this retrospective cohort study, we analysed the incidence and functional outcome of a distal tibiofibular synostosis. Patients with an isolated AO type 44-B or C fracture of the ankle who underwent surgical treatment between 1995 and 2007 were invited for clinical and radiological review. The American Orthopaedic Foot and Ankle Society score, the American Academy of Orthopaedic Surgeons score and a visual analogue score for pain were used to assess outcome. A total of 274 patients were available; the mean follow-up was 9.7 years (8 to 18). The extent of any calcification or synostosis at the level of the distal interosseous membrane or syndesmosis on the contemporary radiographs was defined as: no or minor calcifications (group 1), severe calcification (group 2), or complete synostosis (group 3). A total of 222 (81%) patients were in group 1, 37 (14%) in group 2 and 15 (5%) in group 3. There was no significant difference in incidence between AO type 44-B and type 44-C fractures (p = 0.89). Severe calcification or synostosis occurred in 21 patients (19%) in whom a syndesmotic screw was used and in 31 (19%) in whom a syndesmotic screw was not used.(p = 0.70). No significant differences were found between the groups except for a greater reduction in mean dorsiflexion in group 2 (p = 0.004). This is the largest study on distal tibiofibular synostosis, and we found that a synostosis is a frequent complication of surgery for a fracture of the ankle. Although it theoretically impairs the range of movement of the ankle, it did not affect the outcome. Our findings suggest that synostosis of the distal tibiofibular syndesmosis in general does not warrant treatment.