Effect of fibular rotation and sagittal shift on postoperative function in ankle fractures with syndesmotic injury

To evaluate whether postoperative radiographic and functional outcomes in ankle fractures with syndesmotic injury are associated with a CT-based grading system based on fibular rotation (FR) and sagittal shift distance (SSD), and to assess the influence of surgical timing and patient-related factors on prognosis.

This retrospective cohort study included 370 patients with ankle fractures and syndesmotic injury treated with open reduction and internal fixation between June 2021 and September 2024. Based on preoperative CT measurements, patients were classified into three groups: Group A (FR < 5° and SSD < 2 mm), Group B (5° ≤ FR ≤ 10° or 2 mm ≤ SSD ≤ 5 mm), and Group C (FR > 10° or SSD > 5 mm). Radiographic reduction quality, loss of reduction at 6 months, functional outcomes (SF-36, AOFAS, VAS, ankle range of motion), complications, and reoperations were compared. Inverse probability of treatment weighting and propensity score matching were applied. Multivariate logistic regression was used to identify independent predictors of poor prognosis (final AOFAS < 80), and interaction analyses were performed.

Patients with high-grade syndesmotic malalignment (Group C) had significantly poorer radiographic reduction, higher rates of loss of reduction, complications, and reoperation, and inferior functional outcomes compared to Groups A and B (all P < 0.001). Multivariate analysis identified older age, surgical delay, diabetes, higher body mass index, Weber C fracture, posterior malleolar fracture, and loss of reduction at 6 months as independent risk factors for poor prognosis. A significant interaction was observed between syndesmotic injury grade and surgical delay.

CT-based FR/SSD grading is useful for identifying high-risk syndesmotic malalignment in ankle fracture. Postoperative outcomes are primarily influenced by patient characteristics, fracture pattern, surgical timing, and maintenance of reduction, underscoring the importance of timely surgery and stable syndesmotic reduction, particularly for more severe injuries.