Bony adaptation signs are predictive of anterior head-neck offset remodeling after internal fixation for slipped capital femoral epiphysis: a multicenter study on 217 patients (228 hips) with follow-up until end of growth.

BACKGROUND AND PURPOSE  We aimed to evaluate the prognostic value of radiographic factors in predicting femoral head-neck remodeling, cam deformity, and local growth disturbances in slipped capital femoral epiphysis (SCFE) treated with internal fixation (IF) with or without simultaneous closed reduction.

METHODS  A retrospective multicenter study on 217 SCFE patients (228 hips) treated with IF in 10 institutions was performed. Hip morphology was assessed using preoperative, postoperative, and end of growth (EG) radiographs and radial MRI scans. Evaluated parameters included: epi-metaphyseal distance, Southwick angle (SA), head-neck offset (HNO), femoral neck varus deformity, and shortening. Depending on the presence of bony adaptation (BA; defined as rounded anterior metaphyseal edge and posterior callus formation, typically indicating slip onset > 4 weeks) at diagnosis hips were divided into Group A (n = 96; without BA) and Group B (n = 132; with BA).

RESULTS  At EG, Group A demonstrated better slip correction, more favorable femoral neck remodeling, and lower risk of residual cam deformity than Group B (15% vs 58%, risk difference -43%, 95% confidence interval -54 to -32). Remodeling occurred in most cases in both groups, but normal values were not uniformly reached. Femoral neck varus deformity and shortening were observed in both groups and attributed to disease-specific growth plate damage rather than transphyseal fixation.

CONCLUSION  Radiographic signs of BA at diagnosis can predict the risk of cam deformity at EG. Cases without BA have a favorable prognosis, whereas slips with BA have a higher risk of residual deformity. Signs of BA demonstrated a higher predictive value (0.84) than SA > 40° (0.60) or negative HNO < -5 mm (0.57).