EP1.35 Single-Screw Versus Double-Screw In-Situ Fixation in High-Grade Unstable Slipped Capital Femoral Epiphysis: A Retrospective Comparative Study

Abstract

Abstract Background High-grade unstable slipped capital femoral epiphysis (SCFE) poses a significant surgical challenge, carrying a substantial risk of avascular necrosis and early-onset degenerative joint disease. The optimal fixation strategy, particularly whether a single-screw construct provides outcomes equivalent to double-screw fixation in severe slips, remains a subject of ongoing debate. Methods We retrospectively analyzed 68 patients diagnosed with unstable SCFE between 2011 and 2019. Following exclusion of 24 patients with Grade 1 slips (Wilson classification), 44 patients (Grade 2 and 3) with a minimum follow-up of 24 months were included in the final analysis. The cohort consisted of 41 males and 3 females with a mean age of 13.0 years (range, 9–16 years). The left hip was affected in 36 patients and the right in 8. The mean Southwick slip angle was 60° (range, 33–99°), comprising 34 Grade 2 and 10 Grade 3 slips. All patients underwent attempted gentle reduction; as no clinically meaningful reduction was achieved in any case, in-situ fixation was performed uniformly. Patients were equally allocated to single-screw (n=22) and double-screw (n=22) fixation groups. Primary radiographic outcomes included Tönnis grade progression, femoral neck shortening, and loss of femoral head sphericity at final follow-up. Results At two-year follow-up, both groups demonstrated progressive Tönnis grade deterioration, with no statistically significant intergroup difference (p=0.602; mean difference 0.12, 95% CI: −0.31 to 0.55). Femoral neck shortening was observed in 12 patients (54.5%) in the single-screw group and 15 patients (68.2%) in the double-screw group (p=0.488; risk difference −13.7%, 95% CI: −38.5% to 11.1%). Loss of femoral head sphericity occurred in 10 (45.5%) and 11 (50.0%) patients in the single- and double-screw groups, respectively (p=0.534; risk difference −4.5%, 95% CI: −29.8% to 20.8%). Multivariate logistic regression analysis, adjusting for age, sex, slip angle, and slip grade, confirmed that the number of screws was not an independent predictor of adverse radiographic outcomes (OR: 1.18, 95% CI: 0.52–2.67; p=0.691). Conclusion In high-grade unstable SCFE, single-screw in-situ fixation yields radiographic outcomes comparable to double-screw constructs across all evaluated parameters. In the absence of significant outcome differences, and given the advantages of reduced operative time and lower surgical burden, single-screw fixation represents a reasonable and efficacious treatment strategy even in the setting of severe slips.