Verdonschot N, Huiskes R
Institute of Orthopaedics, University of Nijmegen, The Netherlands.
J Bone Joint Surg Br. 1997 Jul;79(4):665-9. doi: 10.1302/0301-620x.79b4.7173.
It has been suggested that the endurance of cemented femoral reconstructions in total hip arthroplasty is affected by the creep of acrylic cement, but it is not known to what extent cement creeps under loading conditions in vivo, or how this affects load transfer. We have simulated the long-term creep properties of acrylic cement in finite-element models of femoral stem constructs and analysed their effects. We investigated whether subsidence rates measured in vivo could be explained by creep of acrylic cement, and if polished, unbonded, stems accommodated creep better than bonded stems. Our findings showed that polished prostheses subsided only about 50 microm as a result of cement creep. The long-term prosthetic subsidence rates caused by creep of acrylic cement are therefore very small and do not explain the excessive migration rates which have sometimes been reported. Cement creep did, however, relax cement stresses and create a more favourable stress distribution at the interfaces. These trends were found around both the bonded and unbonded stems. Our results did not confirm that polished, unbonded, stems accommodated creep better than bonded stems in terms of cement and interface stress patterns.
有人提出，全髋关节置换术中骨水泥固定型股骨重建的耐久性受丙烯酸骨水泥蠕变的影响，但目前尚不清楚在体内加载条件下骨水泥的蠕变程度，以及这如何影响载荷传递。我们在股骨柄结构的有限元模型中模拟了丙烯酸骨水泥的长期蠕变特性，并分析了其影响。我们研究了体内测量的下沉率是否可以用丙烯酸骨水泥的蠕变来解释，以及抛光的、未粘结的柄是否比粘结的柄更能适应蠕变。我们的研究结果表明，由于骨水泥蠕变，抛光假体仅下沉约50微米。因此，由丙烯酸骨水泥蠕变引起的长期假体下沉率非常小，无法解释有时报道的过度迁移率。然而，骨水泥蠕变确实缓解了骨水泥应力，并在界面处产生了更有利的应力分布。在粘结和未粘结的柄周围都发现了这些趋势。就骨水泥和界面应力模式而言，我们的结果并未证实抛光的、未粘结的柄比粘结的柄更能适应蠕变。
