The relationship between chronic ankle instability and variations in mortise anatomy and impingement spurs.

Thirty-five patients undergoing a Bröstrom procedure for ankle instability were studied retrospectively as to the presence or absence of spurs and loose bodies, outcome, and mortise relationships. 100 adult volunteers had their ankles radiographically and clinically examined for spurs, loose bodies, and laxity. 100 patients' ankles with computed axial tomography were examined to define malleolar relationships. The AOFAS Hindfoot scores on the Bröstrom patients with or without spurs were not different. Patients undergoing a Bröstrom procedure had a 3.37 times incidence of spurs and/or loose bodies compared to normal adult population. The incidence of asymmetric but asymptomatic ankle laxity in normal adults was 11%. The fibula has a 38 degree range of position relative to the axis of the talus and the medial malleolus. A posterior fibular position may predispose to injury.