EP1.31 Long-term results of the Modified Dunn Procedure in Slipped Capital Femoral Epiphysis: a minimum of 10-year follow-up

Abstract

Abstract Aims In-situ fixation for slipped capital femoral epiphysis (SCFE) prevents further displacement but fails to correct the proximal femoral deformity, which may lead to femoroacetabular impingement (FAI) and early osteoarthritis (OA). The Modified Dunn Procedure (MDP), restores proximal femoral anatomy with the aim of improving long-term joint preservation. However, evidence beyond mid-term follow-up remains limited. This study evaluates the 10-year survivorship, functional outcomes, and radiographic correction following MDP. Methods A retrospective single-centre review was performed of patients treated with the MDP between 2007 and 2014 for stable or unstable SCFE of any severity. Patients with preoperative avascular necrosis (AVN) were excluded. Primary outcomes were 10-year survivorship free from conversion to total hip arthroplasty (THA) and from radiographic OA progression (≥1 Tönnis grade). Secondary outcomes included patient-reported outcome measures, hip range of motion, clinical signs of FAI, and correction of the Southwick and alpha angles. Kaplan–Meier survival analyses were performed and stratified by slip severity. Results Thirty-five hips (34 patients) completed ≥10 years of follow-up (163 ± 34 months). 10-year THA conversion–free survivorship was 88.6%, decreasing from 100% in mild slips to 86.4% in moderate and 83.3% in severe slips. 10-year OA progression–free survivorship was 82.9%, with rates of 100%, 81.8%, and 66.7% for mild, moderate, and severe slips, respectively. 10-year functional scores were high (mHHS 88.9 ± 4.4; UCLA 8.9 ± 1.6; Merle d’Aubigné–Postel 17.7 ± 0.9). Significant radiographic correction was observed, with the Southwick angle improving from 45.0° to 13.1° and the alpha angle from 85.8° to 50.9°. No postoperative AVN occurred. Conclusion At 10-year follow-up, the MDP achieved excellent functional outcomes and effective deformity correction in SCFE, with high survivorship in mild and moderate slips. However, progression of hip OA was less favorable in severe slips.