Purpose Mild slipped capital femoral epiphyses (SCFE) nevertheless show significant femoral head–neck deformities which may put cartilage and acetabular labrum at risk. Whether this deformity can be restored to normal has not yet been described in the literature. Methods In a prospective follow-up study, 14 patients with mild SCFE underwent in situ fixation with a single 6.5-mm cancellous, partially threaded screw. In 14 patients arthroscopic osteochondroplasty was performed, and in 13 patients pre- and postoperative measurements of the α-angle were made using antero-superior radial magnetic resonance imaging. Results After arthroscopic osteochondroplasty, the mean α-angle decreased from 57° (range 50°–74°) to 37° (range 32°–47°; p < 0.001). Six patients showed beginning degenerative intra-articular changes (four antero-superior cartilage and three antero-superior labrum lesions) at the time of hip arthroscopy. No intra-operative complications occurred. In one patient, arthroscopic debridement was necessary due to arthrofibrosis and persistent pain. Conclusion Arthroscopic osteochondroplasty can successfully correct the antero-superior α-angle in patients with mild SCFE to normal values. Clinical randomized controlled studies with long-term follow-up are required to find evidence of improved functional and radiographic mid- and long-term outcome compared to in situ fixation alone.

Introduction: In situ fixation of mild (epiphyseal–shaft angle <30°) slipped capital femoral epiphysis (SCFE) is a well accepted treatment method. However, the remaining retrotilt morphology represents a CAM type deformity suspected to favour early osteoarthritis by femoroacetabular impingement. Arthroscopic osteochondroplasty during in situ fixation could overcome this disadvantage with limited additional invasiveness. The aim of the present study was to test the hypothesis that α-angles could be improved to normal by arthroscopic osteochondroplasty in addition to in situ fixation. An α-angle[1] less than 55° was considered normal.