Abstract:
This study investigates the influence of femoral anteversion and prosthesis offset on the biomechanical loading of a cemented total hip arthroplasty (THA). The central hypothesis is that variations in these implant parameters can alter the loading of the proximal femur, leading to critical conditions for the bone and the cement mantle, which in turn may increase the risk of aseptic loosening. A validated musculo-skeletal model was used to determine the muscle and joint contact forces during walking and stair climbing, considering two different anteversion angles (4° vs. 24°) and two prosthesis offsets (standard vs. long). These forces were then applied to a finite element (FE) model of a cemented THA. The analysis revealed that stair climbing consistently caused higher bone strains and cement stresses (up to 25% higher) than walking. Variations in anteversion and offset significantly impacted the loading environment, bone strain distribution, and cement stresses. Specifically, increasing anteversion raised cement stresses by up to 52%, while increasing offset caused a smaller increase of up to 5%. The combination of both increased anteversion and offset resulted in the most substantial rise in cement stresses, with an increase of up to 67% during stair climbing. The study found that an increased anteversion and offset, especially in combination, may elevate the risk of implant loosening by raising the number of cement elements within the critical stress range of 3–10 MPa, which is associated with damage accumulation under cyclic loading. The authors conclude that clinical practice should prioritize careful consideration of implant orientation, particularly with respect to femoral anteversion, to improve the longevity of THA.
