Abstract
BACKGROUND: Posterior malleolar fractures play a critical role in ankle fracture stability and joint congruity. While plate and screw fixation are widely used, existing literature has primarily focused on short-term functional outcomes and reduction quality. The long-term impact of the posterior malleolar fixation technique on post-traumatic ankle osteoarthritis, particularly in relation to fracture morphology, remains insufficiently explored. METHODS: This retrospective cohort study included 91 adult patients who underwent surgical fixation of posterior malleolar fractures between 2015 and 2021, with a minimum radiological follow-up of 36 months. Patients were treated with either posterior buttress plate fixation (n=42) or posteroanterior screw fixation (n=49). Ankle osteoarthritis was assessed using the Van Dijk classifica-tion. Fracture morphology was classified according to the Bartoníček system. Functional outcomes were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) score, the Olerud-Molander Ankle Score (OMAS), and ankle range of motion (Prasad classification). Multivariable regression analyses were performed to assess the independent association between fixation method and outcomes. RESULTS: After adjustment for age, body mass index, follow-up duration, fracture morphology, and open fracture status, screw fixation was statistically associated with a higher degree of ankle osteoarthritis compared with plate fixation (OR 11.22, 95% CI 2.17-58.04; p=0.004). However, the wide confidence intervals indicate considerable statistical uncertainty around the magnitude of this effect, likely reflecting the limited number of outcome events. Sensitivity analysis using a dichotomized osteoarthritis outcome yielded consistent results. Subgroup analyses demonstrated that the association between screw fixation and higher osteoarthritis risk was particularly pronounced in complex fracture patterns (Bartoníček types 3-4). Patients treated with plate fixation achieved significantly higher AOFAS and OMAS scores and demonstrated superior ankle range of motion at long-term follow-up. Increasing Van Dijk osteoarthritis grades were strongly correlated with worse functional outcomes. CONCLUSION: Posterior buttress plate fixation was associated with a significantly lower risk of long-term post-traumatic ankle osteoarthritis and superior functional outcomes compared with screw fixation. These findings were especially evident in complex posterior malleolar fracture patterns, highlighting the importance of fracture morphology and fixation strategy in long-term joint preservation.