STRESS ANALYSIS OF CEMENTLESS TOTAL HIP REPLACEMENT BY FINITE ELEMENT METHOD USING BOUNDARY FRICTION LAYER AND BOUNDARY ELEMENT METHOD

无骨水泥全髋关节置换术初始固定需要生物力学稳定性。采用边界无摩擦层的二维有限元方法对种植体-骨界面应力、骨表面应力和种植体位移进行了分析。增加茎长和茎粗可减少种植体-骨界面应力集中和皮质骨的应力屏蔽作用。考虑到股管弯曲的形状，希望柄远端端位于股管峡部的下端，使柄在股管内的填充率更高。继发性骨关节炎股骨管的应力分布与正常股骨的应力分布有很大不同。这些结果表明，股骨近端管形状对无骨水泥柄的生物力学固定有影响。为了确定生物力学稳定的无骨水泥柄的设计，使用髋关节计算机断层扫描分析股骨近端管的几何形状。正常髋关节组（N组）19例（34髋），骨关节炎髋关节组（OA组）27例（44髋）。N组下小粗隆至峡部距离、峡部管径、峡部面积、内侧皮质拟合圈与股骨长度成正比，说明股骨近端延髓管存在比例性。另一方面，在OA组中，只有内侧皮质贴合圈与股骨长度成正比。OA组的偏移量（p<0.05）、峡部管径（p<0.02）显著小于N组，股骨前倾（p<0.01）、颈轴角度（p<0.01）显著大于N组。建议非骨水泥股骨假体的设计和尺寸应符合股骨近端管形状的变化。

It is required to make biomechanical stability for initial fixation of cementless total hip replacement. Implant-bone interface stresses,bone surface stresses and displacements of implants were analyzed by two-dimensional finite element method using boundary frictionless layer by G essou. Increasing the stem length and the stem thickness result in the reduction of implant-bone interface stress- concentration and the stress-shielding of cortical bones. Considering the curved shape of femoral canal, it is desirable that the distal tip of stem is located in the lower end of fenoral canal isthaus, and that the stem filling ratio in the femoral canal is higher. S tress distributions in the secondary osteoarthritic femoral canal were very different from those in the normal femur. These results indicated that the proximal femoral canal shape was influenced on the biomechanical fixation of cementless stems.To decide the design of the biomechanicaly stable cementless stems, the proxygal femoral canal geometry was analyzed using the Computed Tomography of the hip joints.19 cases(34hips)in normal hip joint group(N group)and 27 cases (44 hips) in osteoarthritic hip joint group(OA group)are examined. In the N group, off set, distance from the below lesser trochanter to the isthmus, canal diameter and area of the isthmus, medial cortex fitted circle was proportional to femoral length, so the proportionality exists in the proxymal femoral sedullary canal. On the other hand,in the OA group, only medial cortex fitted circle was proportional to femoral length. Off set(p<0.05), canal diameter of the isthmus(p<0.02)was significantly smaller and femoral anteversion(p<0.01), angle of neck axis(p<0.01)vas significantly larger in OA group than in N group. It was suggested that the non-cemented femoral prosthesis should have the design and sizes to correspond to the variations of the proxymal femoral canal shapes.