膝关节活动单髁假体衬垫形状及安装位置对置换后膝关节应力分布影响的有限元分析

Finite element analysis of the effect of knee movable unicompartmental prosthesis insertion shape and mounting position on stress distribution in the knee joint after replacement

在单髁置换手术中,市面上可供选择的单髁假体种类较多,常见的衬垫与股骨假体接触面一致性与否,会对置换后的膝关节应力分布产生不同的影响。单髁置换术后胫骨平台内侧断裂以及衬垫脱位是常见的两种失效形式,原因之一是单髁假体在膝关节中的安装位置不匹配,可能导致失效。故本文主要研究衬垫与股骨假体接触面的形状及单髁假体的安装位置对置换后膝关节应力分布的影响。首先,本文建立了正常人体膝关节有限元模型,通过应力和变形两种方式验证了该模型的有效性。其次,建立了两种不同形状衬垫膝关节假体模型(A型和B型),模拟分析在单腿站立情况下,两种衬垫5种内外翻安装位置的膝关节应力分布情况。结果表明,在1 kN轴向载荷下,衬垫峰值接触压力、前交叉韧带峰值等效应力、外侧半月板峰值接触压力,这3种参数A型均比B型小,5种内外翻安装位置下A型在内翻3°时衬垫变形、衬垫峰值接触压力、胫骨峰值等效应力、前交叉韧带峰值等效应力均最小。单髁置换时,建议假体内翻6°以内,选择A型或B型衬垫,需结合患者的其他因素综合分析选择。综上所述,本文研究结果或可降低单髁置换后衬垫脱位、胫骨内侧平台断裂的风险,以期为单髁假体设计提供生物力学参考。

In unicompartmental replacement surgery, there are a wide variety of commercially available unicompartmental prostheses, and the consistency of the contact surface between the common liner and the femoral prosthesis could impact the stress distribution in the knee after replacement in different ways. Medial tibial plateau fracture and liner dislocation are two common forms of failure after unicompartmental replacement. One of the reasons is the mismatch in the mounting position of the unicompartmental prosthesis in the knee joint, which may lead to failure.Therefore, this paper focuses on the influence of the shape of the contact surface between the liner and the femoral prosthesis and the mounting position of the unicompartmental prosthesis on the stress distribution in the knee joint after replacement. Firstly, a finite element model of the normal human knee joint was established, and the validity of the model was verified by both stress and displacement. Secondly, two different shapes of padded knee prosthesis models(type A and type B) were developed to simulate and analyze the stress distribution in the knee joint under single-leg stance with five internal or external rotation mounting positions of the two pads. The results showed that under a 1 kN axial load, the peak contact pressure of the liner, the peak ACL equivalent force, and the peak contact pressure of the lateral meniscus were smaller for type A than for type B. The liner displacement, peak contact pressure of the liner, peak tibial equivalent force,and peak ACL equivalent force were the smallest for type A at 3° of internal rotation in all five internal or external rotation mounting positions. For unicompartmental replacement, it is recommended that the choice of type A or type B liner for prosthetic internal rotation up to 6° should be combined with other factors of the patient for comprehensive analysis. In conclusion, the results of this paper may reduce the risk of liner dislocation and medial tibial plateau fracture after unicompartmental replacement, providing a biomechanical reference for unicompartmental prosthesis design.