The outcome of in-situ fixation of unstable slipped capital femoral epiphysis.

There is limited information regarding the outcome of in-situ fixation of unstable slipped capital femoral epiphysis (U-SCFE). We aimed to report the outcome of a cohort of patients with U-SCFE that were treated with in-situ fixation, by comparing it to the outcome of patients with stable slipped capital femoral epiphysis (S-SCFE). After Institutional Review Board approval, a retrospective analysis of patients with SCFE that were treated with in-situ fixation at a single institution between 2005 and 2016 was performed. Preoperative and postoperative clinical and radiographic data was collected. The rate of complications, including avascular necrosis (AVN), and the presence of impingement were recorded. The outcome of U-SCFEs was compared to that of S-SCFEs. A total of 184 SCFEs in 154 patients (64% male; mean age 11.9 years) with a mean follow-up of 27 months were included. The SCFE was classified as stable in 90.2% of cases, and unstable in 9.8% of. The mean duration of symptoms prior to presentation was 3.2 months. The mean Southwick slip angle at the time of presentation was 33°. A single screw was used to fix all S-SCFEs, while U-SCFEs were treated with either one (66.7%) or two (33.3%) screws. For U-SCFEs, the joint was decompressed at the time of surgery by either needle aspiration or small capsular incision. The final range of motion of the affected hip was comparable in both groups. The overall rate of impingement was 29%. The rate of impingement in S-SCFE and U-SCFE was 27.6 and 44.4%, respectively (P = 0.1). Eight patients required a subsequent surgery (4.4%), all of whom originally have had a S-SCFE. Radiographic signs of AVN of the femoral head were seen in 2.2% of cases. The incidence of AVN of the femoral head in S-SCFEs and U-SCFEs was 1.2 and 11.1%, respectively (P = 0.04). The results of this study support previous findings that the risk of AVN is significantly higher in U-SCFE as compared to S-SCFEs.