A modified Dunn osteotomy without surgical hip dislocation for severe slipped capital femoral epiphysis: mid-term outcomes from a case series

Severe slipped capital femoral epiphysis (SCFE) remains challenging to manage because residual deformity after in situ fixation may predispose patients to femoroacetabular impingement and early osteoarthritis, whereas corrective procedures such as modified Dunn osteotomy via surgical hip dislocation carry a risk of avascular necrosis. We aim to evaluate mid-term outcomes of a modified Dunn osteotomy performed without surgical hip dislocation for SCFE. We retrospectively reviewed 11 patients (14 hips) with severe SCFE treated with modified Dunn osteotomy without surgical hip dislocation between 2015 and 2022. The mean follow-up was 56.0 ± 29.8 months. Clinical outcomes were evaluated using the Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index, while radiographic outcomes included slip angle, α angle, and Tönnis grade. The mean preoperative slip and α angles were 69.3 ± 8.2 and 86.6 ± 18.8°, respectively, improving significantly to 8.5 ± 5.5 and 32.5 ± 7.5° at the latest follow-up. All hips remained Tönnis grade 0 without radiographic progression of osteoarthritis. The mean Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index scores were 95.5 ± 10.5 and 94.5 ± 11.5, respectively. One patient with acute unstable SCFE developed avascular necrosis; no cases of femoroacetabular impingement or implant-related complications were observed. Modified Dunn osteotomy without surgical hip dislocation provided substantial deformity correction and favorable mid-term functional and radiographic outcomes. Avoiding hip dislocation while preserving the retinacular soft-tissue flap and ligamentum teres may help protect femoral head vascularity.