Finite element analysis of femoral stress changes after total hip arthroplasty / 中华骨科杂志

ABSTRACT

Objective To determine the biomechanical variation in full-length femoral stress pat-tern and periprosthetic femoral stress distribution after implantation either with Charnley Elite cemented prostlesis or Summit proximal porous cementless femoral prosthesis. Methods Three-dimensional finite element models of intact femur, Charnley Elite and Summit femoral prostheses were developed. The stress distributions on the femur and the implants were measured. Applied with hip joint loading and related muscles strength, the stress changes of an intact femur and those implanted with either Charnley Elite or Summit protheses, especially changes in proximal femur, were respectively quantitatively analysed. Results Com-pared with intact femur, there was no change of the full-length femur stress pattern in implantation of both implants, the areas of peak values were all presented at middle and lower regions of the femur, and femoral stress value levels were decreased with both implants. Both prostheses induced significant decrease of stress in the periprosthetic bone tissue, the most serious loss of stresses all appeared at femoral calcar, the stress-shielding rates of Elite and Summit prostheses were 90.8% and 95.3% respectively. The distributions of stress shielding of both prostheses were consistent each other, the Summit proximal porous cementless pros-thesis had more serious stress decrease than the Charnley Elite cemented prosthesis. Conclusion Implan-tation of both implants may cause significant stress shielding in the proximal femur. This may be related with periprosthetic bone loss and aseptic loosening of stems, and can be used to explain the mechanism of post-operative femoral fracture and thigh pain. Both implants designs need further improvement to reduce stress changes in proximal femur.