The effect of a porous stemmed hip prosthesis on a Thai femur compared with a general stemmed hip prosthesis using finite element analysis.

Hip replacement surgery is a treatment for patients with hip osteoarthritis. Currently, the common femoral stem of a hip prosthesis is a solid figure made from a titanium alloy (Ti). However, this design often has a short lifespan due to the difference in stiffness between the femur and femoral stem. This discrepancy results in atrophy of the surrounding bones attached to the femoral stem and loosening of the stem. Additionally, the solid figure stem hinders the regeneration and self-repair of the surrounding bones. To address these problems, a scaffold structure with a porous design resembling cancellous bone was utilized to develop a new type of femoral stem. In this research, two variations of the femoral stem were designed, differing in porosity: axially graded with enhanced distal porosity (AGS) and radially graded with increased inward porosity (RGS). These designs were compared to a solid figure stem using the method of finite elements to analyze their effects on a femur and various femoral stem configurations of the hip prosthesis. The results indicated that the AGS femoral stem exhibited a minimal maximum equivalent total strain on a femur compared to the RGS femoral stem and the solid figure stem. Furthermore, the maximum von Mises stress occurring in the femoral stem of AGS was lower than that in the RGS femoral stem and the solid figure of a femoral stem. This outcome is attributed to the graded pore sizes along the longitudinal axis, which support regeneration of bone and cartilage tissues on joint surfaces. Cell types in each location require an appropriate pore size, leading to better distribution of load to the surrounding bones. Therefore, an axially graded femoral stem with increased distal porosity (AGS) is crucial for facilitating multi-tissue regeneration. [ABSTRACT FROM AUTHOR]