单髁置换过程中胫骨假体立柱长度对膝关节生物力学的影响

Effect of tibial prosthesis riser length on knee biomechanics after unicompartmental knee arthroplasty

背景:膝关节单髁置换手术能有效治疗膝关节单侧严重骨关节炎,临床上发现单髁置换后容易发生胫骨后侧骨皮质断裂,断裂始于胫骨截骨的龙骨槽处,胫骨假体立柱长度影响单髁置换后膝关节的生物力学结果。目的:探讨单髁置换中胫骨假体立柱长度对膝关节生物力学的影响,找出假体立柱长度与患者胫骨前后径的关系。方法:选取37岁无膝关节疾病史健康女性志愿者的计算机断层扫描图像数据和常用单髁假体,建立自然膝关节模型并建立单髁假体模型。建立8种不同长度的胫骨假体立柱,最小长度为31 mm,最大长度为34.5 mm,以0.5 mm递进,与医院常使用假体立柱长度33.2 mm进行对比。股骨组件和胫骨组件的材料是钴铬钼合金,胫骨衬垫材料是超高分子量聚乙烯。使用有限元分析软件在股骨上方加载1000 N观察膝关节的生物力学变化。结果与结论:①胫骨假体立柱长度为33 mm时胫骨应力最小,前交叉韧带应力最小,外侧半月板应力最小,股骨假体应力最小;余下各部件应力都较小;②受试者本身胫骨内侧平台前后径长度为53 mm,通过计算比例,胫骨假体立柱长度占胫骨前后径最佳比应为62%左右,如果低于此值可能会发生假体无菌性松动,如果高于此值,则胫骨前后端的骨皮质有发生断裂的可能性。

BACKGROUND:Unicompartmental knee arthroplasty can effectively treat severe unilateral knee osteoarthritis.It has been found that posterior tibial cortical fracture is prone to occur after unicompartmental knee arthroplasty.The fracture begins at the keel groove of tibial osteotomy.The tibial prosthesis riser length affects the biomechanical results of the knee joint after unicompartmental knee arthroplasty.OBJECTIVE:To investigate the effect of tibial prosthesis riser length on knee biomechanics in unicompartmental knee arthroplasty,and to find out the relationship between prosthesis riser length and anterior and posterior tibial diameters of patients.METHODS:Computed tomography image data and commonly used unicompartmental prostheses were selected from a 37-year-old healthy female with no history of knee disease.A natural knee joint model was established and a unicompartmental prosthesis model was built.Eight different lengths of tibial prosthesis risers were established,with a minimum length of 31 mm and a maximum length of 34.5 mm in 0.5 mm increments,for comparison with the commonly used hospital prosthesis riser length of 33.2 mm.The material of the femoral component and tibial disc was cobalt-chromium-molybdenum alloy,and the tibial spacer was ultra-high molecular weight polyethylene.The biomechanical changes of the knee joint were observed using finite element analysis software loaded with 1000 N over the femur.RESULTS AND CONCLUSION:(1)The tibial stress was minimal at a tibial prosthesis riser length of 33 mm;the anterior cruciate ligament stress was minimal;the lateral meniscus stress was minimal,and the femoral prosthesis stress was minimal.The remaining components were less stressful.(2)The subject’s medial tibial plateau anterior-posterior diameter length was 53 mm,and by calculating the ratio,the optimal ratio of tibial prosthesis riser length to anterior-posterior tibial diameter should be about 62%.If it is lower than this value,aseptic loosening of the prosthesis may occur,and if it is higher than this value,fracture of the bone cortex at the anterior-posterior end of the tibia may occur.