Computational modelling of hip resurfacing arthroplasty investigating the effect of femoral version on hip biomechanics

Aim How reduced femoral neck anteversion alters the distribution of pressure and contact area in Hip Resurfacing Arthroplasty (HRA) remains unclear. The purpose of this study was to quantitatively describe the biomechanical implication of different femoral neck version angles on HRA using a finite element analysis. Materials and methods A total of sixty models were constructed to assess the effect of different femoral neck version angles on three different functional loads: 0 degrees of hip flexion, 45 degrees of hip flexion, and 90 degrees of hip flexion. Femoral version was varied between 30 degrees of anteversion to 30 degrees of retroversion. All models were tested with the acetabular cup in four different positions: (1) 40 degrees /15 degrees (inclination/version), (2) 40 degrees /25 degrees, (3) 50 degrees /15 degrees, and (4) 50 degrees /25 degrees. Differences in range of motion due to presence of impingement, joint contact pressure, and joint contact area with different femoral versions and acetabular cup positions were calculated. Results Impingement was found to be most significant with the femur in 30 degrees of retroversion, regardless of acetabular cup position. Anterior hip impingement occurred earlier during hip flexion as the femur was progressively retroverted. Impingement was reduced in all models by increasing acetabular cup inclination and anteversion, yet this consequentially led to higher contact pressures. At 90 degrees of hip flexion, contact pressures and contact areas were inversely related and showed most notable change with 30 degrees of femoral retroversion. In this model, the contact area migrated towards the anterior implant-bone interface along the femoral neck. Conclusion Femoral retroversion in HRA influences impingement and increases joint contact pressure most when the hip is loaded in flexion. Increasing acetabular inclination decreases the area of impingement but doing so causes a reciprocal increase in joint contact pressure. It may be advisable to study femoral neck version pre-operatively to better choose hip resurfacing arthroplasty candidates.

Automated summary

This study used finite element analysis to investigate the biomechanical effects of different femoral neck version angles on Hip Resurfacing Arthroplasty. The results showed that femoral retroversion increases impingement and joint contact pressure, while increasing acetabular inclination can reduce impingement but leads to higher joint contact pressure.