Risk factors for recurrent stress fractures in athletes

Our aim was to identify factors predisposing athletes to multiple stress fr actures, with the emphasis an biomechanical factors. Our hypothesis was tha t certain anatomic factors of the ankle are associated with risk of multipl e stress fractures of the lower extremities in athletes. Thirty-one athlete s (19 men and 12 women) with at least three separate stress fractures each, and a control group of 15 athletes without fractures completed a questionn aire focusing on putative risk factors for stress fractures, such as nutrit ion, training history, and hormonal history in women. Bone mineral density was measured by dual-energy x-ray absorptiometry in the lumbar spine and pr oximal femur. Biomechanical features such as foot structure, pronation and supination of the ankle, dorsiflexion of the ankle, forefoot varus and valg us, leg-length inequality, range of hip rotation, simple and choice reactio n times, and balance in standing were measured. There was an average of 3.7 (range, 3 to 6) fractures in each athlete, totaling 114 fractures. The fra cture site was the tibia or fibula in 70% of the fractures in men and the f oot and ankle in 50% of the fractures in women. Most of the patients were r unners (61%); the mean weekly running mileage was 117 km. Biomechanical fac tors associated with multiple stress fractures were high longitudinal arch of the foot, leg-length inequality, and excessive forefoot varus. Nearly ha lf of the female patients (40%) reported menstrual irregularities. Runners with high weekly training mileage were found to be at risk of recurrent str ess fractures of the lower extremities.