人工股関節における荷重伝達 : モデル実験および数値解析によるセメント材の縦弾性係数の影響 Load Transfer between Femur and Prosthesis following Total Hip Replacement : Experimental and Analytical Study on the Effect of the Cement Property

We investigate here the load transfer between femur and prosthesis following total hip replacement. First, compression tests using a human cadaveric femur are conducted. Then plaster models for the femur are made from the molds taken from the femur. We believe thet the plaster model femur can allow us to distinguish the minute differences affected from experimental setups. Utilizing the five kinds of cementing materials and the two kinds of prosthesis stems, the effects of the modulus of the cementing materials to the strain distribution on the model femur are examined. Further, a numerical analysis method based on the beam theory is proposed, and the load transfer problems between femur and prosthesis are solved by the Runge-Kutta method. The numerical results obtained are in good agreement with the experimental results, which indicates that the distal load transfer between femur and prosthesis takes place in a manner similar to that between two beams. Both the experimental and analytical results predict that the strain distribution induced on the femur with implanted prosthesis differs from the physiological one considerably; i. e. the strain at the calcar is maximum before implantation whereas the strain at the distal point become dominant after implantation. It may be concluded that the stress shielding can't be avoided as long as the presently available prostheses are utilized.