Reduction of Posterior Malleolus Fractures With Open Fixation Compared to Percutaneous Treatment

BACKGROUND: Operative decision making between approaches to posterior malleolus reduction remains a challenge. The purpose of this study is to compare the quality of reduction between percutaneous and open reduction of posterior malleolus fractures and to identify factors associated with malreduction. METHODS: Operatively managed ankle fractures that included posterior malleolus fixation were reviewed. Fracture characteristics were determined on preoperative CT scans. Initial postoperative radiographs were used to measure reduction of the posterior malleolus articular surface and graded as satisfactory (<2 mm step-off) or malreduced (≥2 mm step-off). Final postoperative PROMIS scores and 1-year complications were compared between percutaneous and open cohorts. A multivariate stepwise regression model was used to evaluate predictors for malreduction. RESULTS: A total of 120 patients were included. Open reduction was performed in 91 (75.8%) compared with 29 (24.2%) who underwent percutaneous reduction. Malreduction (≥2-mm articular step-off) occurred in 11.7% of patients. Malreduction rates were significantly higher with percutaneous fixation than open fixation (24.1% vs 7.7%, P = .02). Multiple fragments and those with ≥5 mm of displacement demonstrated higher malreduction rates with percutaneous fixation (P < .05 for both), whereas single fragments and those with <5 mm of displacement experienced similar malreduction rates with percutaneous or open fixation. Initial displacement ≥5 mm (relative risk [RR] = 3.8, 95% CI = 1.2-11.5, P = .02) and percutaneous treatment (RR = 4.1, 95% CI = 1.6-10.5, P < .01) were identified as independent risk factors for malreduction. There were no significant differences in 1-year complication rates or final PROMIS scores between groups. CONCLUSION: Open reduction of the posterior malleolus may lead to improved fracture reduction compared to percutaneous reduction without significant increase in complications. Open fixation improves reduction among fractures with multiple fragments or ≥5 mm of displacement, whereas fractures with a single fragment or <5 mm of displacement achieve similar reductions regardless of approach. Initial displacement ≥5 mm and percutaneous reduction are independent risk factors for malreduction. LEVEL OF EVIDENCE: Level III, therapeutic.