Five years of ankle fractures grouped by stability.

Categories of displaced and undisplaced stable ankle fracture are well recognised. We report on a further group of ankle fractures which are undisplaced at presentation, but do not fulfil criteria for stable injuries, and therefore, may be at risk of displacement. The Blackburn Foot and Ankle Service operates evidence-based guidelines for ankle fractures, introduced in 1998. These were prospectively applied to 306 skeletally mature patients (308 fractures) following classification of the ankle fracture based upon clinical examination and radiography (mortise and lateral views). One hundred and forty-eight (48.4%) of fractures were stable, including 63 male and 85 women, median age 53 years (14-92). Eighty-eight (28.8%) of fractures were undisplaced but potentially unstable based on criteria, including 53 men and 35 women, median age 42 years (14-93). Seventy (22.9%) of fractures were displaced, including 41 men and 29 women, median age 44 years (16-94). Undisplaced, unstable fractures were treated mostly in below-knee casts with immediate weight-bearing and follow-up radiography. Two fractures in this group subsequently displaced requiring fixation according to AO principles. The risk of displacement in potentially unstable fractures is 2.3%. The unstable fracture groups, whether displaced or not, were similar in age/sex profile.