Good long-term outcome of the untreated contralateral hip in unilateral slipped capital femoral epiphysis

Purpose There is no consensus regarding prophylactic fixation of the contralateral hip in slipped capital femoral epiphysis (SCFE). In order to further study this question, we evaluated the long-term natural history of untreated contralateral hips. Methods Forty patients treated for unilateral SCFE without evidence of subsequent contralateral slip during adolescence were reviewed with a mean follow-up of 36 years (range 21–50 years). The deformity after SCFE may demonstrate radiographic signs of cam-type femoroacetabular impingement. We, therefore, measured a-angles in the contralateral hips on anteroposterior (AP) and frogleg lateral radiographs. The angles were compared with those of a control group of adults without SCFE. Five years after the radiographic examination, with a mean follow-up of 41 years, all patients were evaluated by telephone interview. As range of motion and deformity could not be examined, a modified Harris hip score (HHS) (maximum score of 91 points) was used. A modified HHS \76 points and/or radiographic osteoarthritis (OA) was classified as a poor long-term outcome. Results The mean value of the AP a-angle was significantly higher in the contralateral hips in SCFE patients than in the control group (55 vs. 46 ), while the mean value of the lateral a-angle was not. Abnormally high values for one or both a-angles were found in 16 contralateral hips (40 %), of which five patients had abnormal values for both a-angles and were considered to have had an asymptomatic contralateral slip. Five patients (13 %) had a poor outcome in the contralateral hip, of which three patients (8 %) had OA. There was a significant association between hips with both a-angles that were abnormal and poor outcome. Conclusions Since the natural history showed good longterm radiographic and clinical outcome in 35 of 40 patients and only three had OA, we conclude that routine prophylactic fixation of the contralateral hip is not indicated.