The most important determinant in the treatment of malleolar fractures is stability. Stable fractures have an intact deep deltoid ligament and do not displace with functional treatment. If the deep deltoid/medial malleolar complex is disrupted, the talus is at risk of displacement. Weber (2010) showed that weightbearing radiographs predicted stability in patients with undisplaced ankle fractures.

We developed clinical criteria for potential instability and applied them to a prospective series of patients. Criteria included: medial clear space of < 4mm; medial tenderness, bruising or swelling; a fibular fracture above the syndesmosis; a bimalleolar or trimalleolar fracture; an open fracture; a high-energy fracture mechanism. A consecutive, prospectively documented series of 37 patients chose functional brace treatment of potentially unstable fractures. Weightbearing radiographs were performed in the brace before treatment, and free of brace at clinical union (6–9 weeks in all patients). Patients were encouraged to bear full weight and actively exercise their ankles in the brace.

All fractures healed without displacement. The risk of displacement was 0% (95% CI 0–11.2%). This preliminary series gives support for the use of weightbearing radiographs to guide treatment of undisplaced ankle fractures.