髋臼缺损翻修中所用移植材料的有限元分析

Finite element analysis of the grafts used for acetabular revision in the presence of bone loss

背景:髋臼翻修中所用的移植物材料是影响假体稳定的重要因素之一,目前异体冻干骨是较常选用的移植材料。但使用固体颗粒材料修补骨缺损时宿主骨与移植骨之间的缝隙是不可避免的,而这些缝隙可削弱移植骨与宿主骨间的整合过程。使用骨水泥材料可以填补这些缝隙,并且达到快速、完全的固定。但是使用骨水泥代替异体冻干骨颗粒填补假体置入后的空隙对于假体和材料自身应力的影响尚无文献报道。目的:采用有限元法比较分析骨水泥和冻干异体骨颗粒联合三翼翻修假体修复髋臼后的应力分布情况,进而了解选用不同移植材料对三翼髋臼假体稳定性的潜在影响。方法:建立三翼翻修假体及缺损髋臼的有限元模型,翻修假体置入后,缺损部的空隙分别使用骨水泥和冻干异体颗粒骨两种材料填充。于2158N和426N髋关节力作用下,观察移植物自身应力及其对翻修假体应力的影响。结果与结论:在不同髋关节力下三翼髋臼假体金属壳两侧界面的应力变化规律相同,假体所受的最大应力取决于髋关节力的大小和方向。翼部应力的分布规律均是由翼的边缘向翼根部逐渐增大,至翼根与球壳连接处为最大。使用不同移植材料对假体的应力分布无明显影响,但骨水泥所受的各种应力大于冻干骨颗粒的应力。故从材料的稳定及其对假体长期稳定性的影响方面来看,采用冻干骨颗粒移植修补髋臼缺损要优于骨水泥。

BACKGROUND：Alternative implants affect stability of prostheses,and freeze-dried bone allografts are most selected as implants.The crack between grafts and host bone is unavoidable,which would weaken the bone integration.Bone cement can fill the cracks quickly and completely,however,the effects of bone cement on the stress of prostheses and its own remains poorly understood.OBJECTIVE：To evaluate the effect of the different grafting for bone loss in the presence of the new acetabular component with wings at the time of acetabular revision.METHODS：The finite-element models of acetabular component with three wings and acetabulum with bone loss were established.Following prostheses implantation,the gaps were filled with bone cement and freeze-dried bone allograft,respectively,stress of the graft and its effect on prostheses were analyzed under 2 158 N and 426 N acetabular loads.RESULTS AND CONCLUSION：The finite-element analysis demonstrated that stress and strain at the interfaces of bone-shell and metal-polyethylene liner had the same direction of change but no significant difference between them.In the study,the result indicated increased contact stresses with an increased hip force and orientation.The stress of wings increased gradually from rim to root.Its peak stress was at the joint between the wing and the shell.The different grafts did not affect the stress of the acetabular component.But the stress of bone cement was significantly higher than that of particulate bone.The study demonstrated that change of the graft could not make remarkable effect on the stress of the acetabular component.But the stress of bone cement increased significantly.The result of the finite-element analysis indicated that particulate bone graft is benefit to improving its stability and to minimize aseptic loosening rate of acetabular component.