Kim Do-Gyoon, Miller Mark A, Mann Kenneth A
Department of Orthopaedic Surgery, Institute for Human Performance, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
J Orthop Res. 2004 May;22(3):633-40. doi: 10.1016/j.orthres.2003.09.007.
Fatigue damage from activities of daily living has been considered to be a major cause of aseptic loosening in cemented total hip arthroplasty. The cement-bone interface is one region where loosening could occur, but to date the fatigue response of the interface has not been examined. Cement-bone specimens were prepared from fresh frozen human cadaver tissue using simulated in vivo conditions. Tensile fatigue tests to failure were performed in an environmental chamber. Loss of specimen stiffness (stiffness damage) and permanent displacement after unloading (creep damage) were found in all specimens. At failure, creep damage accounted for the majority (79.9+/-10.6%) of the total strain damage accumulation at failure (apparent strain, epsilon=0.0114+/-0.00488). A power law relationship between strain-damage rate and time-to-failure showed that the strain-damage rate was an excellent predictor of the fatigue life of the cement-bone interface. The S-N response of the interface was obtained as a function of the applied stress ratio and the initial apparent strain. The total motion between cement and bone (72.2+/-29.8 microm) prior to incipient failure due to both stiffness and creep fatigue damage may be sufficient to result in fibrous tissue formation and contribute to eventual clinical loosening.
日常生活活动导致的疲劳损伤被认为是骨水泥型全髋关节置换术中无菌性松动的主要原因。骨水泥-骨界面是可能发生松动的一个部位，但迄今为止，该界面的疲劳反应尚未得到研究。利用模拟的体内条件，从新鲜冷冻的人体尸体组织制备骨水泥-骨标本。在环境试验箱中进行拉伸疲劳试验直至失效。在所有标本中均发现了标本刚度的损失（刚度损伤）和卸载后的永久位移（蠕变损伤）。在失效时，蠕变损伤占失效时总应变损伤累积量的大部分（79.9±10.6%）（表观应变，ε=0.0114±0.00488）。应变损伤率与失效时间之间的幂律关系表明，应变损伤率是骨水泥-骨界面疲劳寿命的一个极佳预测指标。界面的S-N响应是作为施加应力比和初始表观应变的函数获得的。由于刚度和蠕变疲劳损伤，在初始失效之前，骨水泥与骨之间的总位移（72.2±29.8微米）可能足以导致纤维组织形成，并促成最终的临床松动。
