膝关节单髁置换术后关节线位置对内外侧间室应力影响的生物力学研究

Biomechanical research on effects of joint line height on stress of medial and lateral compartment after unicompartmental knee arthroplasty

目的 通过有限元分析法探讨膝关节单髁置换不同关节线位置对膝关节产生的生物力学效应,为膝关节内侧间室单髁置换临床手术选择提供生物力学依据.方法 根据正常志愿者（男性,30岁,165 cm,60 kg）膝关节CT扫描数据和单间室膝关节假体三维扫描数据构建正常膝关节和单髁置换三维模型.基于对象特异性非均匀材料属性赋值方法,构建正常膝关节和3种不同关节线位置（-3 mm、0mm和3 mm）的内侧间室单髁置换有限元模型.以胫骨关节面为起始面,从上往下每隔2 mm取1截面,共取5个截面.分别在5个截面的内外侧平台面各均匀选取30个节点,以节点等效应力平均值表示内外侧胫骨平台软骨下骨的应力水平,以定量比较不同模型间应力水平差异.结果 聚乙烯垫片上表面应力均值在0、-3和＋3 mm关节线高度分别为14.84、26.81和20.86 MPa,组间的差异均有统计学意义（t0vs-3=4.896,P0vs-3=0.000;t0vs＋3=3.455,P0v＋3=0.008;t-3vs＋3=2.579,P-3vs＋3=0.020）.胫骨侧假体上表面应力均值在0、-3和＋3 mm关节线高度分别为29.69、50.49和39.99 MPa,组间的差异均有统计学意义（t0vss-3=5.675,P0vs-3=0.000;t0vs＋3=4.755,P0V＋ 3=0.001;t-3vs＋3=4.783,P-3vs＋3=0.000）.当关节线处于0mm高度时,胫骨平台内外侧应力水平与正常膝关节最为接近;当关节线处于-3 mm高度时,内侧聚乙烯垫片和胫骨假体上表面接触应力相比于0 mm关节线位置,分别增加81％和70％,而外侧胫骨平台松质骨的应力增加8.7％;当关节线处于＋3 mm高度时,聚乙烯垫片和胫骨假体上表面接触应力相比于0mm关节线位置的增幅较-3 mm关节线小,分别为41％和35％.而外侧胫骨平台松质骨的应力相比于0 mm关节线下降55.6％.结论 在膝关节单髁置换中,只有保持良好的关节线位置,才有助于保证膝关节内外侧间室的应力水平和传递路径同正常膝基本一致,从而降低聚乙烯垫片的过早磨损、胫骨假体下沉以及假体周围骨折的风险.

Objective To investigate biomechanical effects of different joint line height on unicompartmental knee arthroplasty （UKA） and to provide biomechanical evidence for surgical decision during UKA using finite element analysis （FEA）.Methods On the basis of knee joint CT data from a healthy volunteer （male,30 years old,165 cm and 60 kg） and UKA prosthesis 3D scanned data,the 3D models of normal knee and UKA were constructed.Subject-specific finite element models with inhomogeneous material property assignment were constructed for normal knee and UKA with 3 different height of joint line （-3 mm,0 mm and ＋3 mm）.Starting from the tibial articular surface,5 sections were extracted with 2 mm interval.30 nodes were selected in medial and lateral area,respectively on each section.The mean stress value of nodes was defined as the stress level of subchondral bone.Results Mean values of stress on polyethylene upper surface of 0,-3 and＋3 mm joint line position were 14.84,26.81and 20.86 MPa,and the difference was statistical significant （t0vs-3=4.896,P0vs-3=0.000;t0vs＋3=3.455,P0v＋3=0.008;t-3vs＋3=2.579,P-3vs＋3=0.020）.Mean values of stress on tibial prosthesis upper surface of 0,-3 and ＋3 mm joint line position were 29.69,50.49 and 39.99MPa,respectively,and the difference was statistical significant（t0vs-3=5.675,P0vs-3=0.000;t0vs＋3=4.755,P0v＋3=0.001;t-3vs＋3=4.783,P-3vs＋3=0.000）.When joint line was in 0 mm height,stress level of subchondral bone was similar to that of normal knee.When joint line was in-3 mm height,significantly increased stress was found on polyethylene （increased 81%） and tibial component （increased 70%） surface compared with that of 0 mm height,while stress on trabecular bone under lateral tibial articular surface also increased by 8.7%.When joint line was in ＋3 mm height,increased stress on polyethylene （increased 41%） and tibial component （increased by 35%） surface were less than that of-3 mm height.Stress on trabecular bone under lateral articular surface decreased by 55.6% compared with 0 mm height.Conclusion During UKA,ensuring a normal height of joint line is benefit to keep the stress path of the medial and lateral tibia similar with normal knee and decrease the risk of premature polyethylene wear,tibial component subsidence and periprosthetic fracture.