Overgrowth of the femoral neck after hip fractures in children

Background: Overgrowth after pediatric femoral shaft fractures is well documented; however, overgrowth of the femoral neck after hip fractures has not been especially reported previously. The purpose of this study was to evaluate the incidence and characteristics of femoral neck overgrowth after hip fractures in children. Methods: From January 1990 to December 2012, there were 30 consecutive patients with pediatric hip fractures. We retrospectively reviewed the medical record of all the patients, including age at injury, gender, injury mechanism, fracture type, methods of treatment, time to bony union, and complications. The functional outcome was evaluated by Ratliff's criteria. The radiography of the pelvis was performed in controlled positions of abduction and external rotation. The length of the femoral neck was measured by two observers. The overgrowth of the femoral neck was defined as lengthening more than 3 mm in comparison with the uninjured hip. Results: At a mean follow-up of 4.9 years (range 2-8 years), 12 patients (40 %) had an overgrowth of the femoral neck. The average overgrowth of the femoral neck was 6.2 mm (range 3.2-8.5 mm). The patients with femoral neck overgrowth were younger (p = 0.0002), have lower rate of avascular necrosis of the femoral head (p = 0.0006), and have better functional outcome (p = 0.0026). Conclusions: Our results provide evidence that overgrowth of the femoral neck following hip fractures may occur in children and the overgrowth phenomenon in the femoral neck was a predictor of good outcomes after treatment.