Biomechanical study of the design parameters in THA stems.

• Main Authors: Liu Chun Ping, 劉俊平
• Other Authors: Chen Weng Pin
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/09556946775137127912

碩士 === 中原大學 === 醫學工程學系 === 87 === The effects of design parameters in THA stems on the proximal femoral load transfer were investigated using both experimental strain gauge measurement and finite element analysis on synthetic femora. Three-dimensional finite element models for an intact femur and femora implanted with two different prostheses were constructed from the same experimental models used. Four design parameters in the THA stems were studied: (1) stem geometry, (2) fixation method, (3) stem material property, and (4) stem length. The stress-shielding effects at the proximal femur were investigated for the following conditions: (1) implantation of a straight Corin stem and a curved PCA stem with three different fixation methods (non-cemented, proximal-one-third-cemented, and fully- cemented), (2) Ti alloy was used for the Corin and the PCA stems instead of Co-Cr alloy, (3) the length of the Corin stem was shortened from 15 cm to be 11 cm as the PCA stem. Results for the strain measurements and the finite element analyses showed good agreements and thus verified the validity of the current study. The following conclusions were reached from both the experimental and the finite element analysis results: (1) the stress- shielding effects in the medial sites are more significant than the lateral sites under all insertion conditions, (2) the stress-shielding effect is most significant for a femur implanted with a non-cemented, Co-Cr PCA stem, (3) the application of bone cement tends to decrease stress-shielding effect and normalizes the stress distribution for both the PCA and the Corin prostheses, (4) the least significant stress-shielding effect was found for the shorter, Co-Cr Corin stem with proximal-one-third-cemented fixation. Besides, the convergence of the finite element model was validated and the contact behavior between the implant and the bone or cement was incorporated in the analysis. Through this biomechanical study on the design parameters in THA stems, valuable information can be provided for the evaluation of currently used or newly developed prostheses. Keywords: THA stem, Stress-shielding effect, Biomechanical experiment, finite element analysis.