Torsional Strength of Single–versus Double–screw Fixation in a Model of Unstableslipped Capital Femoral Epiphysis

INTRODUCTION: Slipped capital femoral epiphysis (SCFE) is the most common hip disorder of adolescent children [1]. It results in fracture of the growth cartilage, separating the proximal femoral epiphysis from the metaphysis, due to hormonal and mechanical factors [2]. The most widely accepted treatment for stable SCFE (defined by the ability to bear weight on the affected limb) has been a single centrally placed cannulated cancellous bone screw. The treatment of unstable SCFE (defined as the inability to bear weight) is more controversial with some advocating double-screw fixation [3]. A torsional component has been suggested for the mechanical basis of SCFE fractures [4,5]. If this is true then single-screw fixation would be less resistant to torsional loading than double-screw fixation. The objective of this study was to determine the relative torsional strength of the femoral capital growth plate after singleor double-screw fixation in an in vitro pig model of SCFE.