Shear Strength of Allograft Bone Screw Fixation in Slipped Capital Femoral Epiphysis

Introduction: Slipped capital femoral epiphysis (SCFE) is the most common hip disorder affecting adolescent children [1]. The etiology is thought to be multifactorial, related to both biological and biomechanical factors [2]. SCFE occurs when the epiphysis of the proximal femur slips in relation to the metaphysis through the growth plate, causing pain, disability and potential long-term sequellae from joint incongruity. The current standard treatment for SCFE is percutaneous fixation using a single steel screw with the goal of preventing further slippage and obtaining early physeal closure. Bone allograft epiphyseodesis is an alternative treatment method in which a beam-shaped freeze-dried cortical allograft is placed percutaneously into a drill hole through the cortex, up the femoral neck and into the femoral head [3]. Allograft epiphysiodesis avoids the need for a second surgery to remove the hardware, but has the disadvantage that it cannot achieve stability until the allograft is incorporated into the surrounding bone. We hypothesized that a threaded cortical bone allograft could provide sufficient initial stability to serve as a viable alternative to the steel implant. The objective of this study was to compare the fixation strength of a single threaded bone allograft versus a single steel screw in an in vitro pig model of SCFE.