定制型股骨近段假体的骨水泥三维有限元模型研究

Three-dimensional Finite Element Analysis Responsible to Bone Cement with Customized Prosthesis of Proximal Segmental Femur

目的建立股骨近段大段骨缺损及定制型股骨近段假体的三维有限元模型,分析不同柄长的股骨近段假体柄植入髓内后对股骨-骨水泥的应力分布的影响。方法通过CT扫描数据建立股骨近段130mm骨缺损不同髓内柄长度(140mm、120mm、100mm、80mm、60mm)的定制型假体的三维有限元模型。模拟下肢单足行走进行负荷加载,分析股骨-骨水泥的应力分布。结果骨水泥应力由近端向远端逐渐增加,在假体柄末端附近达到最大值。当髓内柄长度为140mm时,骨水泥层内、外侧最大应力值分别为2.5MPa和5.5MPa,均小于骨水泥自身强度,可以有效避免因高应力而导致骨水泥的碎裂。结论股骨近段假体髓内柄要有足够长度,以减少骨水泥所受应力,防止因骨水泥碎裂而出现假体松动。对于股骨近段130mm的骨质缺损,采用髓内柄长为140mm骨水泥型股骨近段人工假体重建能够有效减少骨水泥层压力,从而避免因骨水泥发生疲劳碎裂而导致假体松动的危险。

Objectives To create three-dimensional finite element models for the large defect of proximal femur and the customized prosthesis of proximal segmental defect femur, and to analyze the influence on the stress distribution of femur-cement after the intramedullary implantation of different stem length prostheses. Methods Three-dimensional finite element models were established for the large defect of proximal femur and proximal femoral segmental prostheses with different stem-lengths （140 mm, 120 mm, 100 mm, 80 mm and 60 mm）. The influence on stress distribution of femur-cement was analyzed for the different stem-length prostheses implanted. Results The stress on bone cement gradually increased from proximal end to distal end, and reached its highest value near the tip of prostheses. The prostheses with stem lengths of 120 mm, 100 mm, 80 mm and 60 mm could bring the cement mantle stress to the value beyond the fatigue strength of cement. Only when the intramedullary stem-length of prosthesis was 140 mm, the stress on the cement mantle was under the fatigue strength of cement. Conclusion The intramedullary stem of the proximal femoral segmental prosthesis must have enough length to decrease the stress on the cement mantle in order to avoid the prosthesis loosening.