Modified Dunn Technique for Unstable Slipped Capital Femoral Epiphysis: A Midterm Single Center Experience.

Objective  To evaluate the safety and reproducibility of the surgery for unstable slipped capital femoral epiphysis (SCFE) through the modified Dunn technique in a single center cohort from Brazil. Methods  We retrospectively analyzed a cohort of patients submitted to this procedure by a single surgeon who was a hip preservation specialist. Demographic data and radiographic angles were evaluated for the relative risk (RR) of avascular necrosis (AVN) using a log-binomial regression model with simple and random effects. Results  Among the 30 patients (30 hips) with a mean age of 11.79 years at the time of the operation, there were 17 boys and 18 left hips, which were operated on in a mean of 11.5 days after the slip. The mean follow-up was of 38 months. The preoperative Southwick angle averaged 60.69° against 4.52° postoperatively ( p  < 0.001). A larger preoperative slip angle was associated with the development of AVN (RR: 1.05; 95% confidence interval [95%CI]: 1.02-1.07; p  < 0.01). The overall AVN rate was of 26.7%. Function was good or excellent in 86% of uncomplicated hips, and poor in 87.5% of the partients who developed AVN, as graded by the Harris Hip Score. There was no statistical relationship between epiphyseal bleeding and AVN development ( p  = 0.82). Conclusion  The modified Dunn technique is associated with restoration of the femoral alignment and function after unstable SCFE, when uncomplicated. Moreover, it was shown to be reproducible in our population, with a rate of 26% of femoral head necrosis.