Rotational Dynamics of the Distal Tibiofibular Joint After Operative Treatment of Ankle Fractures With Syndesmosis Injury

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Background:Syndesmosis injury healing remains poorly understood, despite its high prevalence in ankle fractures. Unstable syndesmosis is commonly addressed with either syndesmosis screw (SS) or suture button (SB) fixation, and up to 20% of operated ankle fractures may require some form of syndesmosis fixation. However, in biomechanical studies no repair technique fully restores the preinjury rotational stability or the anatomical alignment of the tibiofibular joint.Methods:In a study of 39 patients with operatively treated supination external-rotation type 4 and pronation external-rotation type 4 ankle fractures and fixation of an unstable syndesmosis, weightbearing cone beam computed tomography with rotational stress was performed on both ankles at a mean follow-up of 7.8 (range, 6.2-10.3) years to evaluate tibiofibular syndesmosis dimensions and fibular rotation. Sagittal translation of the fibula (ST), anterior width (AW) and posterior width (PW) of the syndesmosis, tibiofibular clear space (TFCS), and fibular rotation (RO) were measured in neutral position and in maximal internal and external rotation. Mean change in measurements between maximal rotations were calculated to represent range of motion of the fibula under rotational stress.ResultsTwenty-six patients had screw fixation (SS) and 13 had suture button (SB) fixation of the syndesmosis. Eight SSs had been removed and 3 were broken. No SBs had been removed. The mean Olerud-Molander Ankle Score was 84.7 (SD 20.3). Fibular rotation demonstrated a mean difference of 2.7 degrees (95% CI, 1.3-4.1; P < .05) compared with the patient’s non-injured ankle. Other measurements showed no significant differences; however, we lacked statistical power to detect significant changes in ST, AW, PW, and TFCS.ConclusionExcess fibular rotation persists after healing of ankle fractures with fixed unstable syndesmosis. However, clinical relevance remains unclear and should be explored with larger patient groups.