Abstract
BACKGROUND: Hip resurfacing arthroplasty (HRA), a viable alternative to total hip arthroplasty (THA), is often constrained by postoperative complications that are closely related to the orientation of femoral prosthesis. Although avoiding varus placement is widely accepted, the optimal prosthesis orientation remains unclear. This study aims to determine the optimal orientation of femoral prosthesis in HRA from a biomechanical perspective. METHODS: A three-dimensional finite element model of the hip joint was developed based on CT data and incorporated a Birmingham Hip Resurfacing prosthesis. Five orientations were simulated: 30° varus, 15° varus, neutral, 15° valgus, and 30° valgus. A physiological load of 2100 N was applied to evaluate contact pressure, peak von Mises stress (VMS), and principal strain distributions in both the prosthesis and proximal femur. RESULTS: At 30° varus, the highest peak VMS (204.0 MPa) and strain (6.12 × 10⁻(3)) were observed, along with elevated contact pressure (146.14 MPa). At 15° varus, contact pressure further increased (165.76 MPa), whereas both VMS and strain decreased compared with 30° varus. The neutral orientation reduced all parameters moderately (contact pressure: 109.11 MPa; VMS: 93.8 MPa; strain: 1.74 × 10⁻(3)). 15° valgus exhibited the most favorable profile, with the lowest contact pressure (88.94 MPa), reduced VMS (78.2 MPa), and minimal strain (1.62 × 10⁻(3)). Although 30° valgus further decreased VMS (65.0 MPa), it increased strain and contact pressure (164.49 MPa; 2.43 × 10⁻(3)), suggesting potential overloading. Overall, 15° valgus provided the most balanced mechanical performance. CONCLUSION: A 15° valgus orientation may represent the biomechanically optimal position for femoral prosthesis placement in HRA, effectively minimizing mechanical stress and strain while preserving physiological load transfer patterns. These findings offer practical guidance to enhance implant longevity and reduce the risk of postoperative complications.