Outcome of in situ pinning in patients with unstable slipped capital femoral epiphysis: Assessment of risk factors associated with avascular necrosis

Introduction: Avascular necrosis (AVN) is a devastating complication following treatment of unstable slipped capital femoral epiphysis (SCFE). The advent of newer methods such as open reduction and surgical dislocation of the hip has increased the debate on the optimal method of treatment. However, the risk or predisposing factors for AVN remain unclear. We aimed to assess the outcome of in situ fixation and the risk factors associated with AVN. Methods: We retrospectively reviewed the records of 27 patients (27 hips) with unstable SCFE out of the 280 children managed for SCFE from 1995 to 2006. The mean age in years of the patients at surgery was 12.2±1.58, and our sample comprised 70.4% males, and 29.6% females, with a mean follow-up of 3.1±1.9 years. Univariable and multivariable binomial regression models were used to assess factors predisposing to AVN. Results: AVN occurred in 22.2% (6/27) of the children with unstable SCFE. After adjustment for age, race, and time to surgery, sex and preoperative slip angle were the only 2 significant factors related to an increased risk of AVN, risk ratio (RR)≤4.15, 95% confidence interval≤1.00-17.19, P≤0.05 and RR≤1.04, 95% confidence interval≤1.00-1.07, P≤0.03, respectively. Female children constitute a high-risk group for AVN in this subgroup. Conclusions: AVN is still prevalent among patients with unstable SCFE who underwent in situ pinning. Female sex and slip magnitude are potential predisposing factors for developing AVN. Level of Evidence: Level III (retrospective cohort study).