Aims The aims of this study were to evaluate the abductor function in moderate and severe slipped capital femoral epiphysis (SCFE), comparing the results of a corrective osteotomy at the base of the femoral neck and osteoplasty with 1) in situ epiphysiodesis for mild SCFE, 2) contralateral unaffected hips, and 3) hips from healthy individuals. Patients and Methods A total of 24 patients (mean age 14.9 years (sd 1.6); 17 male and seven female patients) with moderate or severe SCFE (28 hips) underwent base of neck osteotomy and osteoplasty between 2012 and 2015. In situ epiphysiodesis was performed in seven contralateral hips with mild slip. A control cohort was composed of 15 healthy individuals (mean age 16.5 years (sd 2.5); six male and nine female patients). The abductor function was assessed using isokinetic dynamometry and range of abduction, with a minimum one-year follow-up. Results We found no differences in mean peak abductor torque between the hips that underwent osteotomy and those that received in situ epiphysiodesis (p = 0.63), but the torque was inferior in comparison with contralateral hips without a slip (p < 0.01) and hips from control individuals (p < 0.001). The abduction strength was positively correlated with the range of hip abduction (R = 0.36; p < 0.001). Conclusion Although the abductor strength was not restored to normal levels, moderate and severe SCFE treated with osteotomy at the base of the femoral neck and osteoplasty showed abductor function similar to in situ epiphysiodesis in hips with less severe displacement. Cite this article: Bone Joint J 2018;100-B:1524–32.

Objective: To compare the clinical outcomes between patients with moderate and severe slipped capital femoral epiphysis (SCFE) treated with osteotomy at the base of neck and osteoplasty and with healthy individuals. Methods: Comparative cohort with 12 patients (14 hips) with moderate and severe SCFE who underwent osteotomy at the base of neck and osteoplasty between 2007 and 2014. The mean age at surgery was 13.3 ± 2.5 years and the mean follow-up was 3.8 ± 2.2 years. We assessed the level of hip pain by the visual analog scale (VAS) and anterior impingement test (AIT); the level of function using the Harris Hip Score (HHS) and 12-Item Short Form Health Survey (SF-12), the range of motion (ROM) by goniometry and Drehmann sign, and the hip muscular strength by isokinetic and Trendelenburg sign. Results: The level of pain was slightly higher in the SCFE cohort compared with healthy hips (VAS, 0.8 ± 1.4 vs 0 ± 0, 0.007; AIT, 14% vs 0%, p = 0.06; respectively). No differences were observed between the SCFE and control cohort for the functional scores (HHS, 94 ± 7 vs 100 ± 1, p = 0.135); except for ROM, with increased internal rotation (37.3º ± 9.4º vs 28.7º ± 8.2º, p < 0.001), and strength, with decreased abduction torque (75.5 ± 36.9 Nm/Kg vs 88.5 ± 27.6 Nm/Kg, p = 0.045) in the SCFE cohort. Conclusion: The osteotomy at the base of neck and the osteoplasty restored the hip motion and muscle strength, except for the abductor strength, to near normal levels, representing a viable option for the treatment of moderate and severe SCFE. Level of Evidence III, Ambidirectional Cohort Study.