Comparison of the efficacy of posterior-anterior screws, anterior-posterior screws and a posterior-anterior plate in the fixation of posterior malleolar fractures with a fragment size of ≥ 15 and < 15%

BACKGROUND: Different fixation methods have been used to treat posterior malleolar fractures (PMFs), but the clinical efficacy of different fixation methods in the treatment of PMF with different fragmentation has rarely been reported. The purpose of this study was to investigate the efficacy of posterior-anterior (PA), anterior-posterior (AP) screws and PA plate in the fixation of PMFs with a fragment size of ≥15 and < 15%. METHODS: This is a retrospective study of the clinical data of 243 patients with a unilateral ankle fracture involving the posterior malleolar ankle fracture. All patients were divided into two groups based on their fragment size, ≥15% (n = 136) and < 15% (n = 107). After reduction of PMF under direct vision via a posterolateral approach, posterior-anterior (PA), anterior-posterior (AP) screws and PA plate were used for fixation of PMF in the two groups. Briefly, for fixation of PMF with PA screw, two to three 3.5-mm (Depuy Synthes, Switzerland) cannulated screws were placed from the posterior to anterior direction; for fixation with PA plate, a 3.5-mm reconstruction plate (Depuy Synthes, Switzerland) was placed from the posterior to anterior direction, and for fixation of PMF with an AP screw, two to three 3.5-mm screws were placed from the anterior to posterior direction. All patients were followed up at 1, 3, 6, and 12 months after surgery and thereafter at 6-month intervals. The primary outcomes were AOFAS and ROM, which were recorded at the final follow-up. RESULTS: The average follow-up time for all patients was 18.9 months (range 12–36 months), and all fractures healed. In fragment size ≥15% group, the average AOFAS score of patients treated with PA, AP screws and posterior plate were 91.5, 91.8, and 90.8, respectively, and the average limited ankle-dorsiflexion ROM was 5.0 °, 5.4 ° and 5.6°, respectively, at the last follow-up, there was no significant difference between the three fixation methods in terms of AOFAS scores and ankle ROM (P > 0.05). In fragment size < 15% group, the average AOFAS score of patients treated with PA, AP screws and posterior plate were 92.3, 91.9, and 84.1, respectively, the average limited ankle-dorsiflexion ROM were 5.1 °, 4.7 °, and 6.3 °, respectively, at the last follow-up. There were statistically significant differences in AOFAS scores and ankle ROM between posterior plate fixation and PA, AP screw fixation (P < 0.05); while no significant difference was found between PA and AP screw fixation (P > 0.05). CONCLUSION: For PMFs with fragment size ≥15%, there was no significant difference in the outcomes between the three fixation methods. For PMF with fragmentation < 15%, the PA and AP screws both provided good fixation.