Screw start point and orthogonal relationship to the physis do not impact clinical outcomes for in-situ fixation of slipped capital femoral epiphysis.

Abstract

In-situ screw fixation (ISSF) is the gold standard for treatment of slipped capital femoral epiphysis (SCFE). While central screw placement within the epiphysis is known to reduce the risk of intra-articular penetration, the impact of the screw starting point on the proximal femur and the resulting screw trajectory relative to the proximal femoral physis on radiographic or clinical outcomes remains unclear. This study evaluated whether screw starting point or inclination affects outcomes following ISSF. A retrospective review was performed of SCFE patients treated with ISSF at a single institution between 2008 and 2023. Demographic data, postoperative hip pain, early complications, and reoperations were recorded. Radiographic parameters included screw starting point, screw inclination angles, Southwick angles, number of threads crossing the physis, and epiphyseal screw position. Screw starting points were either anterior screw starting point (ASSP) or lateral screw starting point (LSSP). Outcomes were compared between groups. A total of 177 patients had a mean follow-up of 36 months. ASSP was identified in 83 hips and LSSP in 94 hips. The ASSP group demonstrated a more orthogonal trajectory on both anteroposterior (AP) and lateral views (P < 0.05). The middle third of the epiphysis was engaged more frequently on AP and lateral radiographs in the LSSP group. No significant differences were found in hip pain, complication rates, or reoperations between groups. Although ASSP yields a more orthogonally placed screw relative to the proximal femoral physis compared with LSSP, the overall screw starting point and the orthogonal relationship of the screw to the physis do not impact clinical outcomes or reoperation rate. Level IV.