Optimizing total hip replacement prosthesis design parameter for mechanical structural safety and mobility

Abstract

Femoral acetabular impingement after total hip replacement reduces range of motion (ROM), which leads to dislocation or subluxation problems. Decreasing the head and neck diameters of the hip prosthesis largely influences ROM, but reduced neck diameters increases principal stress. The purpose of study was to develop a design optimization framework for neck diameter to maximize range of motion while simultaneously minimizing the stress throughout the neck cross section. A proximal femur with a hip prosthesis model was developed, and the principal stress was calculated. To optimize the neck diameter, a multi-objective function was developed which minimizes principal stress at the neck while maximizing ROM. Stress was calculated using finite element method, and ROM was mathematically calculated. In this study, neck diameters were optimized for head diameters. A linear equation to calculate optimum neck diameter with respect to the head diameter was proposed. The principal stress of the modified model decreased by 33.6% while maintaining acceptable range of motions. Results show that design parameters, including the neck diameter, head diameter, and neck-to-shaft angle, have trade-off relationships between principal stress and ROM. Therefore, careful determination of the neck diameter is needed to provide adequate mechanical safety and mobility in the THR prosthesis.