Remodelling of femoral head-neck junction in slipped capital femoral epiphysis: a multicentre study

Purpose We examined the remodelling of the femoral head-neck junction in patients with slipped capital femoral epiphysis (SCFE) and the frequency of residual cam deformities. Methods We reviewed 69 hips in 56 patients with stable SCFE who had undergone in situ pinning. Mean age at slip was 11.7 years and the follow-up period 63.4 months. Cam deformity was evaluated using the anterior offset alpha (alpha) angle and head-neck offset ratio (HNOR). Results The average alpha angle and HNOR significantly improved from 76.2 degrees to 51.3 degrees and 0.086 to 0.135, respectively; 25 hips (36.2 %) still had an alpha angle greater than 50 degrees, and 32 hips (46.4 %) had an HNOR of under 0.145. A multivariate analysis selected age at onset and slip angle as risk factors for cam deformity, with cutoff values 11.1 years and 21.0 degrees, respectively. Conclusions Although most hips had remodelling of the head-neck junction, 29.4 % had residual cam deformities that may be susceptible to femoroacetabular impingement.