Influence of posterior malleolar fragment size on clinical function and spatiotemporal gait parameters in trimalleolar ankle fractures.

backgroundPosterior malleolar fractures accompanying trimalleolar ankle injuries may compromise joint stability and lead to long-term functional impairment. However, the impact of posterior malleolar fragment (PMF) size on postoperative functional recovery remains unclear. This study aimed to evaluate the association between PMF size and morphology with postoperative clinical outcomes using both functional scoring systems and smartphone-based gait analysis.

methodsSeventy-two patients who underwent surgical treatment for trimalleolar fractures between 2017 and 2022 and met the inclusion criteria were retrospectively reviewed. Patients were categorized into two groups based on PMF size: <25% and ≥ 25%. Fragment configuration was classified according to the Bartoníček system. Functional outcomes were assessed using AOFAS, FAAM, SF-36, and VAS scores, while gait performance was analyzed through spatiotemporal parameters obtained with the GaitAnalyzer application. Results were compared with an age- and sex-matched control group of 72 healthy individuals.

resultsPatients with PMF ≥ 25% demonstrated significantly higher grades of post-traumatic osteoarthritis (p = 0.020). The < 25% group had significantly better SF-36 physical function (p = 0.040) and FAAM-Sport scores (p = 0.023). No significant differences were observed between groups for AOFAS, FAAM-ADL, or VAS scores (p > 0.05). Compared with controls, both patient groups showed pronounced impairments in gait velocity, step time, step length, and cadence (p < 0.001); however, these parameters did not differ significantly between the PMF < 25% and ≥ 25% groups (p > 0.05). In multivariate regression, FAAM-Sport was independently associated with PMF ≥ 25% (β=-15.589; p = 0.022), the presence of joint step-off (β=-21.338; p = 0.002), and male sex (β=+16.448; p = 0.014). Surgical fixation of the posterior fragment was associated with improved FAAM-Sport scores (β=+17.171; p = 0.046).

conclusionA posterior malleolar fragment size ≥ 25% is associated with a higher incidence of post-traumatic osteoarthritis and greater impairment in sport-related functional activities. In contrast, objective spatiotemporal gait parameters appear to be independent of fragment size. Multivariable analysis demonstrates that functional outcomes are influenced not only by fragment size but also by factors such as the presence of articular step-off and the development of post-traumatic osteoarthritis. These findings indicate that postoperative functional recovery following trimalleolar ankle fractures is a multifactorial process.