Gait Biomechanics after Femoral Nailing of Intertrochanteric Fractures

Abstract

Intertrochanteric fractures of the hip are highly prevalent in the elderly and commonly managed using single and dual lag screw femoral nails. Biomechanical studies show differences between devices in the mechanics of maintaining fracture stability, however, clinical outcomes have been conflicting. An understanding of joint biomechanics and gait following surgical management will allow us to quantify functional outcomes in detail and understand femoral nail parameters that influence joint biomechanics. The central aim of this thesis was to investigate clinical and functional outcomes after femoral nailing of intertrochanteric fractures in the elderly. Following an introduction in chapter one, the second chapter in this thesis was a systematic review and meta-analysis that determined aseptic reoperation rates and failure mechanisms contributing to reoperation in patients managed with single and dual screw devices. This study identified no difference between patients managed with single and dual separated screw devices in reoperation rates. It also identified insufficient clinical outcome data available for patients managed with dual integrated screw devices. The third chapter presented a protocol for a randomised controlled trial investigating the effects of using single or dual integrated screw devices and lag screw locking mode on clinical outcomes. This chapter incorporated the use of gait biomechanics outcomes using objective measures from gait analysis and formed the methodological underpinnings of this thesis. The fourth chapter, a critical methodological component of this thesis, developed an instrumented walking frame and musculoskeletal modelling framework that allowed for gait analysis of walker-reliant individuals. Additionally, effects of including handle-reaction forces on residual forces during modelling were evaluated. Results showed improved estimates of musculoskeletal loads of the torso by reducing residual forces. The fifth chapter investigated changes in joint biomechanics between six weeks and six months post-operative and associations between femoral offset shortening and lateral lag screw protrusion with gait analysis outcomes. Results found improvements in hip, knee and ankle biomechanics between six weeks and six months. Additionally, deficiencies in hip abduction and power generation of patients at six months were found in comparison with elderly controls. Results further revealed a moderate association between larger amounts of lateral lag screw protrusion with decreased hip abduction moments at six weeks. In the sixth chapter, hip joint reaction forces were investigated between patients treated with a single and dual integrated lag screw femoral nail. Results showed higher hip joint reaction forces at six weeks in the dual integrated screw group along with an average double peak hip loading profile that was not displayed in the single screw group at this timepoint. Results further indicated higher force generation of the hip abductor muscles in the dual integrated screw group. Additionally, no differences were identified between groups at six months. The collection of studies presented in this thesis provide new detail on functional outcomes following femoral nailing of elderly intertrochanteric fractures by describing gait biomechanics outcomes for the first time. Minimising the amount of lateral lag screw protrusion has been identified as an important factor in maintaining biomechanical outcomes of the hip that are crucial to medio-lateral stability. It also provided evidence that using a dual integrated screw device is associated with superior hip joint loading patterns and force generation of the hip abductors at earlier timepoints when compared to using single lag screw devices. This may be clinically useful in allowing for faster recovery of function in intertrochanteric fracture patients undergoing fracture fixation via proximal femoral nail.