Long-term evolution of slipped capital femoral epiphysis treated by in situ fixation: a 26 years follow-up of 11 hips

Slipped capital femoral epiphysis (SFCE) may lead to femoro acetabular impingement and long-term function impairment, depending on initial displacement and treatment. There are several therapeutic options which include in situ fixation (ISF). The objective of this study was to evaluate long-term functional and radiographic outcomes of patients with SFCE treated with ISF. We conducted a single-center, retrospective study evaluating the clinical and radiographic outcomes of SCFE in situ fixation with a mean follow-up of 26 years (10-47). Analysis of preoperative and last follow up radiographs was performed. The functional status of the hip was evaluated according to the Oxford hip score-12 and the radiographic osteoarthritis stage was rated according to Tönnis classification. Signs of femoro acetabular impingement were sought. Ten patients (11 hips) were included. The average initial slip was 33.5° (10-62). At final follow up, the average Oxford hip score was 19.3 (12-37), it was good for groups who had a small initial slip (16.7) or moderate (17) and fair for the severe group (27). Average Tönnis grade was 1.3 (0-3). The average alpha angle was 65.3° (50-80°). Femoro acetabular impingement was likely in 100% of patients with severe slip, in 50% of patients with moderate slip and in 33% of patients with a slight slip. In situ fixation generated poor functional results, substantial hip osteoarthritis and potential femoro acetabular impingement in moderate to severe SCFE's. However, in cases with minor displacement, functional and radiographic results are satisfactory. The cut off seems to be around 30° slip angle, above which other treatment options should be considered.