Prognostic factors for long-term outcome of chronic slipped capital femoral epiphysis treated with fixation <i>in situ</i>.

Abstract

Predictive factors for long-term outcome after <i>in situ</i> fixation for chronic slipped capital femoral epiphysis (SCFE) have so far not been systematically analysed. The aims of this study were to define predictors for long-term outcome and to assess the association between initial grade of slipping and post-slip deformities. We studied 51 patients (60 hips) with chronic SCFE treated with <i>in situ</i> fixation. There were 31 males and 20 females with a mean age of 12.9 years. The mean follow-up was 39.0 years (21.1 to 56.8). Post-slip deformity was defined as abnormal alpha (a) angles in anteroposterior (AP) and lateral radiographs; AP angle of 74° and lateral angle of 63° were used as cutoffs between normal and abnormal α-angles. Harris hip score (HHS) less than 85 points was classified as a poor clinical outcome and osteoarthritis was a poor radiographic outcome. The mean slip angle was 31.7° (12° to 77°). The mean AP α-angle was 67.4° (36° to 111°) and the mean lateral α-angle was 57.1° (22° to 104°). Post-slip deformities developed in almost one-third of hips with a mild degree of slipping and in about half the hips with more pronounced degrees of slipping. The long-term outcome was good in 40 hips (67%) and poor in 20 hips. A small AP α-angle was the only independent prognostic factor for a good combined clinical and radiographic outcome. Post-slip deformity, defined as an abnormally high AP α-angle, is the most important prognostic factor for poor long-term clinical and radiographic outcome in chronic SCFE treated with <i>in situ</i> fixation.