胫骨平台下低密度区骨量及体积对下肢力线影响的有限元分析

Finite element analysis of the impact of bone mass and volume of low-density area under tibial plateau on lower limb alignment

目的采用有限元分析胫骨平台下低密度区骨量及体积对下肢力线的影响,为临床上胫骨平台下骨量减少的膝关节骨关节炎(knee osteoarthritis,KOA)患者预防下肢力线内移合并膝关节内翻提供力学证据。方法选取1名健康成人为研究对象,获取其X线片和CT影像数据并导入Mimics 21.0软件,重建完整膝关节模型及3个体积相等、形态不同的胫骨平台下低密度区模型,导入Solidworks 2023软件中进行模型装配、验证。分别构建胫骨平台下低密度区骨量减少22%、33%、44%、55%、66%的5个KOA有限元模型及骨量减少66%的低密度区模型等比例缩放81%、90%、100%、110%、121%的5个KOA有限元模型。根据生理状态下人体下肢负荷情况,胫、腓骨远端设置完全固定,在股骨头表面主要负重区施加沿下肢力线方向、大小为1860 N的轴向压强载荷,利用有限元分析软件Abaqus 2022计算分析胫骨平台内侧最大应力及胫骨皮质骨、松质骨最大位移,进而预测下肢力线改变趋势。结果构建的KOA模型符合下肢正常解剖结构。在相同边界条件、相同载荷情况下,随着胫骨平台下低密度区骨量逐渐减少,以及胫骨平台下低密度区体积逐渐增大,胫骨内侧平台最大应力及胫骨皮质骨、松质骨最大位移均随之增大,差异均有统计学意义(P<0.05)。结论胫骨平台下出现低密度区提示膝内翻及下肢力线内移可能性增加,且低密度区体积和骨量减少程度是关键促发因素,可指导临床医生提前预防,避免膝内翻发生。

Objective To investigate the impact of the bone mass and volume of the low-density area under the tibial plateau on the lower limb force line by finite element analysis,offering mechanical evidence for preventing internal displacement of the lower limb force line in conjunction with knee varus in patients with knee osteoarthritis(KOA)and reducing bone mass under the tibial plateau.Methods A healthy adult was selected as the study subject,and X-ray film and CT imaging data were acquired.Mimics 21.0 software was utilized to reconstruct the complete knee joint model and three models representing low-density areas under the tibial plateau with equal volume but varying shapes.These models were then imported into Solidworks 2023 software for assembly and verification.Five KOA finite element models with 22%,33%,44%,55%,and 66%bone mass reduction in the low-density area under tibial plateau and 5 KOA finite element models with 81%,90%,100%,110%,and 121%times of the low-density area model with 66%bone mass loss were constructed,respectively.Under physiological loading conditions of the human lower limb,the distal ends of the tibia and fibula were fully immobilized.An axial compressive load of 1860 N,following the lower limb force line,was applied to the primary load-bearing area on the femoral head surface.The maximum stress within the tibial plateau,as well as the maximum displacements of the tibial cortical bone and tibial subchondral bone,were calculated and analyzed using the finite element analysis software Abaqus 2022.Subsequently,predictions regarding the alteration of the lower limb force line were made based on the analysis results.Results The constructed KOA model accorded with the normal anatomical structure of lower limbs.Under the same boundary conditions and the same load,the maximum stress of the medial tibial plateau,the maximum displacement of the tibial cortical bone and the maximum displacement of the cancellous bone increased along with the gradual decrease of bone mass in the low-density area under the tibial plateau and the gradual increase in the volume of the low-density area under tibial plateau,with significant differences(P<0.05).Conclusion The existence of a low-density area under tibial plateau suggests a heightened likelihood of knee varus and inward movement of the lower limb force line.Both the volume and reduction in bone mass of the low-density area serve as critical initiating factors.This information can provide valuable guidance to clinicians in proactively preventing knee varus and averting its occurrence.