Hip shape and long-term hip function: a study of patients with in-situ fixation for slipped capital femoral epiphysis.

Slipped capital femoral epiphysis (SCFE) is a rare adolescent hip disease that leads to a hip shape abnormality. Typical treatment involves in-situ fixation. It is not known if the degree of initial hip shape abnormality associated with SCFE has a significant effect on long-term hip function. A cohort of patients aged 18-50 who had undergone in-situ fixation for SCFE from 1970 onwards in our institution provided IHOT-33 (hip function) outcome data. Frog lateral radiographs from the time of surgery were used to measure radiological hip shape using both Southwick angle and alpha angle. There were 38 patients (46 hips) SCFE patients who met the eligibility criteria. We obtained follow-up data for 32 patients (38 hips), 83% follow-up. Ten patients (20 hips) had bilateral SCFE. The mean follow-up was 12.7 years (95% CI 10.7-14.7). 32 patients matched for age and sex who had no history of SCFE provided control IHOT-33 outcome data. There was a significant difference (p<0.05) in long-term hip function between patients undergoing in-situ fixation for SCFE and the control population (mean IHOT-33 scores of 71.8 and 95.8 respectively). There was no significant (p>0.05) correlation between long-term hip function and Southwick angle or lateral alpha angle. The initial severity of hip shape abnormality due to SCFE was not a strong predictor of long-term hip function. Other extraneous factors not related to hip shape may have an equally if not more important role to play in the subsequent long-term outcome of SCFE.