Four biomechanical and anthropometric measures predict tibial stress fracture: A prospective study of 1065 Royal Marines

Abstract

Background: Tibial stress fractures cause a significant burden to Royal Marines recruits. No prospective running gait analyses have previously been performed in military settings. Aim: We aimed to identify biomechanical gait factors and anthropometric variables associated with increased risk of TSF. Methods: 1065 Royal Marines recruits were assessed in week-2 of training. Bilateral plantar pressure and 3D lower limb kinematics were obtained for barefoot running at 3.6 m.s-1, providing dynamic arch index, peak heel pressure and lower limb joint angles. Age, bimalleolar breadth, calf girth, passive hip internal/external range of motion and body mass index (BMI) were also recorded. Ten recruits who sustained a TSF during training were compared with 120 recruits who completed training injury-free using a binary logistic regression model to identify injury risk factors. Results: Four variables significantly (p<0.05) predicted increased risk of TSF (odds ratios and 95% CI): smaller bimalleolar width (0.73, 0.58-0.93), lower BMI (0.56, 0.33-0.95), greater peak heel pressure (1.25, 1.07-1.46) and lower range of tibial rotation (0.78, 0.63-0.96). Summary: Reduced impact attenuation and ability to withstand load were implicated in tibial stress fracture risk.