膝关节单髁置换术胫骨假体不同后倾角对假体磨损和功能的影响

Effects of Different Posterior Tibial Slopes in Unicompartmental Knee Arthroplasty on the Wear and Function of Prosthesis

目的建立单髁置换术胫骨假体后倾3°和7°膝关节不同屈膝角度三维有限元模型,研究两种后倾角膝关节生物力学特性和假体磨损及其对功能的影响。方法结合人体膝关节CT与MRI图像和第3代Oxford假体,建立胫骨假体后倾3°和7°下屈膝单髁置换术有限元模型,在股骨内外侧髁中心点上施加1 k N载荷模拟人体站立相负重,分析不同屈膝角度下单髁假体与关节软骨的最大应力及分布。结果0°、30°、60°、90°和120°屈膝角度下后倾3°半月板衬垫最大应力分别比后倾7°增加了28.06%、68.99%、19.45%、21.06%、53.38%,应力分布区域从衬垫侧边向中央区域集中,屈膝120°时应力集中明显。胫骨假体后倾3°单髁假体最大应力均大于后倾7°,应力集中区域的扩大会导致假体的磨损和松动,关节软骨接触应力和集中区域随后倾角增大而增大,在高屈曲角度时应力集中更明显。结论单髁置换术胫骨假体后倾角3°较7°时假体应力和磨损更高,研究结果为临床膝关节单髁置换手术方案设计提供理论依据。

Objective To establish the three-dimensional(3 D)finite element model of unicompartmental knee arthroplasty(UKA)with 3°and 7°posterior tibial slope at different knee flexion angles,and to study biomechanical properties and prosthetic wear of the knee joints with two types of posterior tibia slope and their effects on knee function.Methods Combining CT and MRI images of human knee joints with the 3 rd-generation Oxford prosthesis,the finite element UKA model with 3°and 7°posterior tibia slope were established.The 1 kN load was applied to center point of the medial and lateral condyles of the femur to simulate the standing load of human body.The maximum stresses and distributions of the prosthesis and articular cartilage at different knee flexion angles were analyzed.Results The maximum stress of the meniscus liner with 3°posterior tibia slope at0°,30°,60°,90°,120°knee flexion angles increased by 28.06%,68.99%,19.45%,21.06% and 53.38%,the distribution area was concentrated from the side of the meniscus liner to the central area,and the stress concentration was obvious at 120°knee flexion.The maximum stress of prosthesis with 3°posterior tibia slope was greater than that with 7°posterior tibia slope.The expansion of stress concentration area would cause wear and loosening of the prosthesis,contact stress and concentration area of the articular cartilage would subsequently increase with posterior tibia slope increasing,and stress concentration would be more obvious at high knee flexion angles.Conclusions Tibial prosthesis has the higher stress and greater wear under the condition of 3°posterior tibia slope than 7°posterior tibia slope.The research findings provide theoretical basis for the UKA design in clinic.