Mid-term outcomes of posterior malleolar fracture plating: identifying predictors of adverse outcomes.

Abstract

While surgical fixation of posterior malleolar fractures (PMFs) has become increasingly common, evidence supporting its long-term clinical benefit lags. This study evaluates mid-term functional and radiographic outcomes after posterior plating and identifies predictors of poor prognosis. A consecutive cohort of 82 patients treated with posterior plating for PMFs between 2015 and 2018 was identified. Patients were recalled at a mean follow-up of 87.5 ± 10.3 months to obtain functional scores (AOFAS, OMAS, EQ-5D-VAS) and radiographic osteoarthritis grading. A unique subset of 35 patients, previously analyzed at short-term follow-up (mean 24.7 ± 8.1 months), was re-evaluated to assess longitudinal functional evolution within the same subjects. Multivariable linear regression identified independent risk factors. Fifty-five patients were evaluated (67% response rate). Multivariable analysis identified residual posterior step-off (≥ 1 mm) as a primary independent predictor of lower AOFAS (p = 0.035) and OMAS (p = 0.004) scores, and increased osteoarthritis severity (B = 1.31, p < 0.001). Preoperative CT findings suggestive of anterior syndesmotic involvement (ASI) were independently associated with progressive joint degeneration (B = 0.96, p < 0.001). Longitudinally (n = 35), mean AOFAS scores improved significantly by 15.1 points between short- and mid-term follow-up (72.5 vs. 87.6; p < 0.001), despite radiographic progression of osteoarthritis. Residual posterior step-off is a primary driver of poor mid-term results. Preoperative CT-based ASI is an independent risk factor for progressive radiographic degeneration. Functional recovery continues significantly beyond the 2-year follow-up.