不同模量植入假体与周围骨间的应力分析

Stress analysis between implant prostheses with different moduli and surrounding bones

背景:应力遮挡效应会导致植入假体修复骨缺损手术失败,其主要原因是由于植入假体的弹性模量大于骨组织弹性模量。目的:分析植入假体弹性模量对应力分布的影响,寻求消除应力遮挡现象的方法。方法:通过CT扫描的方式获取实验犬与人体骨组织的模型,分别对其优化后进行梯度赋值,建立较为可靠的骨骼力学模型,并与植入假体组合后进行有限元仿真。首先,通过对比格犬骨骼模型和人体骨骼模型及其对应的植入假体进行有限元仿真,模拟了不同弹性模量对植入假体修复术后的应力和位移分布情况;其次,分析了较小弹性模量差仍会形成应力遮挡现象的原因,建立了骨骼模型及植入假体模型,确立了材料属性赋予方法;最后,验证了该模型及材料属性赋予方法的可行性,并通过随机选取受力点的方式,定量分析植入假体弹性模量与骨骼弹性模量之间的关系对应力遮挡形成的影响。结果与结论:通过梯度赋值法建立与骨骼力学性质更加接近的实验犬骨骼模型和人体骨骼模型,该方法重建的力学模型与真实骨骼的力学性质更为接近;通过有限元仿真力学测试证明,不同弹性模量植入假体对假体本身与周围骨骼间相对位移的影响较小;另外量化弹性模量对假体植入骨骼后对应力分布的影响,可为后续的相关研究提供帮助。

BACKGROUND:Stress shielding can lead to the failure of implant prostheses to repair bone defects,mainly due to the fact that the elastic modulus of the implant is greater than that of the surrounding bone tissues.OBJECTIVE:To explore methods for eliminating the stress shielding by analyzing the influence of the elastic modulus of the implanted prosthesis on the stress distribution.METHODS:The bone tissue models of experimental canine and human bone tissues were obtained by CT scanning,and then were optimized.The gradient assignment was performed to establish a reliable bone mechanics model,and the finite element simulation was performed after the combination with the implanted prosthesis.First,the finite element simulation of experimental canine and human bone tissues and the corresponding implanted prosthesis was performed to simulate the distribution of stress and displacement of prosthesis with different elastic moduli after prosthesis implantation.Second,the reasons for the stress shielding even with small elastic modulus differences were analyzed.The bone and implant prosthesis models were established,and a method for assigning material properties was established.Finally,the feasibility of the model and material property assignment method was verified,and the influence of the relationship between the elastic modulus of the implanted prosthesis and the elastic modulus of the bone on the formation of stress shielding was quantitatively analyzed by randomly selecting the stress points.RESULTS AND CONCLUSION:The mechanical properties of bone models of experimental canine and human bone tissues established by gradient assignment method are close to the actual bones.The finite element simulation mechanics test proved that the implantation of different elastic modulus had less effect on the relative displacement between the prosthesis itself and the surrounding bones.Moreover,quantifying the effects of elastic moduli on the stress distribution after implantation of the prosthesis into the bone will contribute to the research in the future.