Comparison of clinical outcome of pronation external rotation versus supination external rotation ankle fractures.

BACKGROUND: A pronation external rotation (PER) ankle fracture is a relatively uncommon injury. The purpose of this study was to examine the immediate and short-term clinical outcomes of operatively treated PER IV ankle fractures and compare them with a similarly treated cohort of supination external rotation IV (SER IV) fractures.

METHODS: 22 PER IV and 108 SER IV fractures were identified from a single surgeon's prospectively collected database from 2004 to 2010. All patients were treated with fracture fragment and ligament specific fixation during the same time period by the same surgeon. Postoperative radiographs and bilateral ankle computed tomography (CT) scans were reviewed for articular incongruity, syndesmotic malreduction, and loss of reduction. Clinical outcome measures, including the Foot and Ankle Outcome Score (FAOS) and ankle range of motion (ROM), were collected at latest follow-up visit.

RESULTS: There was no difference in the rate of wound complications, fracture nonunion, or loss of reduction between the PER IV and SER IV groups. There was no significant difference in the incidence of postoperative articular incongruity (19% vs 8%, P = .23); however, the PER IV cohort was found to have a significantly higher rate of syndesmotic malreduction (40% vs 18%, P = .04). No clinically or statistically significant differences were detected between the 2 groups in regard to all FAOS domains.

CONCLUSION: In a cohort of operatively treated PER IV fractures, fracture fragment and ligament specific fixation resulted in good short-term outcomes that were comparable to those seen in similarly treated patients with an SER IV fracture pattern. However, a notably greater number of syndesmotic malreductions were noted in the PER IV cohort, and therefore heightened scrutiny is recommended in treating this particular injury pattern.

LEVEL OF EVIDENCE: Level III, retrospective comparative study.