Effects of cement creep on stem subsidence and stresses in the cement mantle of a total hip replacement.
Effects of cement creep on stem subsidence and stresses in the cement mantle of a total hip replacement.
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DOI：
10.1002/(sici)1097-4636(199702)34:2
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发表时间：
1997-02
期刊：
影响因子：
--
通讯作者：
Z. Lu;H. McKellop
中科院分区：
文献类型：
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作者：
Z. Lu;H. McKellop
在骨水泥全髋关节假体中，丙烯酸水泥（聚甲基丙烯酸甲酯，[PMMA]）的蠕变在增加或减少骨水泥套失效几率中的作用一直是一个有争议的话题。在本研究中，我们使用水泥水泥杆的三维有限元模型来评估水泥蠕变对水泥杆沉降的影响，以及水泥在短期和长期循环荷载下的应力和应变。水泥层采用实验得到的齐默规则PMMA水泥的剪切模量和体蠕变模量。茎杆-水泥界面的模型分为(1)完全粘结，(2)完全脱粘且有摩擦，或(3)完全脱粘且无摩擦。在循环荷载作用下，三种粘结条件下都发生了一些水泥蠕变，导致杆的额外下沉和水泥内部应力分量的降低。卸载过程中，界面完全粘结和无摩擦时，可达到完全恢复预加载状态。在摩擦界面处存在残余水泥蠕变、水泥内部残余应力和卸载期间柱的残余沉降；但应力降低幅度不超过13%，沉降量约为0.46 mm。临床经常观察到的脱粘茎的较大下沉可能归因于本模型未包括的因素，如周向骨重塑。
In cemented total hip prostheses, the role of creep of the acrylic cement (polymethyl methacrylate, [PMMA]) in increasing or decreasing the chance of failure of the cement mantle is a subject of ongoing controversy. In the present study we used a three-dimensional finite-element model of a cemented stem to assess the influence of cement creep on subsidence of the stem, and on the stress and strain in the cement under cyclic load, both in the short and long term. The cement layer was assigned the shear and bulk creep moduli of Zimmer regular PMMA cement, which were obtained experimentally. The stem-cement interface was modeled either as (1) completely bonded, (2) completely debonded with friction, or (3) completely debonded and frictionless. Under the cyclic load some cement creep occurred with all three bonding conditions, allowing additional subsidence of the stem and a decrease in the stress components within the cement. During the unloaded period the full recovery of the preload conditions could be reached with the completely bonded and with the frictionless interfaces. With the frictional interface there was residual cement creep, residual stresses within the cement, and residual subsidence of the stem during the unloaded period; however, the reduction of the stress was at most 13% and the subsidence was about 0.46 mm. The much larger subsidence of debonded stems that is often observed clinically might be attributed to the factors which were not included in the present model, such as circumferential bone remodeling.