서강대학교

초록/요약

Reduced range of motion (ROM) in total hip replacement (THR) prosthesis may cause femoral acetabular impingement, and lead to dislocation or subluxation problems. Head and neck diameter of hip prosthesis largely influence ROM, but reduced neck diameter for larger ROM would increase the local principal stress at prosthesis neck. Neck fracture cases of THR has been reported in reason of small neck diameters. Moreover, previous studies were focused on either ROM and cup-stem orientation relationship or only stress analyses of THR prosthesis. Therefore, the purpose of this study was 1) to develop a design optimization framework of THR neck dimension, 2) and to optimize the THR prosthesis neck dimension to maximize ROM while minimizing the stress simultaneously. Computer-tomography image based proximal femur model with hip prosthesis was developed to calculate the principal stress at the prosthesis neck during jogging motion. To optimize neck diameter, a multi objective function was developed which minimizes principal stress at neck while maximizing ROMs including 5 rotation parameters in 3D plane. The function is formed as two terms: stress term and ROM terms. Stress was calculated using finite element method and ROMs were calculated mathematically. In this study, neck diameters were optimized for head diameters by developed optimization framework. Head-to-neck ratio distribution of optimum points at neck-to-shaft angle 125° was from 2.3 to 2.9, which were narrowly distributed than of 130° and 135° with head-to-neck ratio from 2.2 to 3.0. Head and optimum neck diameter relationship equation was developed as linear equation. By using the equation developed, the THR prosthesis selection with optimal neck diameter for patient specific head diameter is possible to prevent neck fracture with acceptable ROMs. We analyzed that by using the developed equation, principal stress generated at neck has been decreased by 33.6% compared to previous study design.