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

非骨水泥型人工全髋关节置换术的初期固定要求具有生物力学稳定性。采用Gessou的边界无摩擦层对种植体-骨界面应力、骨面应力和位移进行了二维有限元分析。随着骨柄长度和粗细的增加，种植体-骨界面应力集中程度降低，皮质骨应力遮挡作用减弱。考虑到股骨管的弯曲形状，股骨干远端应位于股骨管峡部的下端，股骨管内的股骨柄充填率较高。S应力在继发性骨关节炎股骨管中的分布与正常股骨有很大不同。为确定生物力学性能稳定的非骨水泥假体的设计，应用髋关节CT对股骨近端管形态进行了分析，并对19例(34个髋关节)正常髋关节和27例(44个髋关节)骨性关节炎髋关节进行了检查。在N组，股骨小转子下方至峡部的距离、峡部管径及面积、内侧皮质适合圈与股骨长度成正比，说明股骨近端皮质部存在这种比例关系。另一方面，在骨性关节炎组，只有内侧皮质适合的圆与股骨长度成正比。与N组比较，OA组股骨前倾角(p&lt；0.01)、颈轴角度(p&lt；0.01)、峡部管径(p&lt；0.02)显著减小(p&lt；0.05)。建议非骨水泥假体的设计和大小应与股骨干管形状的变化相适应。

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.