Keaveny T M, Bartel D L
Department of Mechanical Engineering, University of California, Berkeley 94720-1740, USA.
J Bone Joint Surg Am. 1995 Jun;77(6):911-23. doi: 10.2106/00004623-199506000-00012.
Long-term biomechanical problems associated with the use of sintered porous coating on prosthetic femoral stems inserted without cement include proximal loss of bone and a risk of fatigue fracture of the prosthesis. We sought to identify groups of patients in whom these problems are accentuated and in whom the use of porous coating may thus jeopardize the success of the arthroplasty. We attempted to develop clinical guidelines for the use of sintered porous coating by investigating the long-term biomechanical effects of bone growth into partially (two-thirds) porous-coated anatomic medullary locking hip prostheses that fit well. More specifically, we used a detailed finite element analysis and a composite beam theory to determine the dependence of proximal loading of the bone and maximum stresses on the stem on the development of clinically observed patterns of bone ingrowth and the dependence of the risk of fatigue fracture of the stem on the diameter of the stem, the diameter of the periosteal bone, and the material from which the prosthesis was made. We found that bone ingrowth per se substantially reduced proximal loading of the bone. With typical bone ingrowth, axial and torsional loads acting on the proximal end of the bone were reduced aa much as twofold compared with when there was no ingrowth; bending loads on the proximal end of the bone were also reduced. The risk of fatigue fracture of the stem was insensitive to the development of bone ingrowth. However, the risk of fatigue fracture of the stem increased with decreased diameters of the stem and the periosteal bone and with increased modulus of the stem. The maximum risk of fracture was found in active patients in whom a cobalt-chromium-alloy stem with a small diameter had been implanted in a bone with a small diameter.
与非骨水泥植入的人工股骨柄使用烧结多孔涂层相关的长期生物力学问题包括近端骨量丢失和假体疲劳骨折风险。我们试图确定这些问题更为突出、使用多孔涂层可能会危及关节置换术成功的患者群体。我们通过研究骨长入部分（三分之二）多孔涂层且适配良好的解剖型髓内锁定髋关节假体的长期生物力学效应，尝试制定烧结多孔涂层的临床使用指南。更具体地说，我们使用详细的有限元分析和复合梁理论，来确定骨近端负荷和假体上最大应力对临床上观察到的骨长入模式发展的依赖性，以及假体疲劳骨折风险对假体直径、骨膜骨直径和假体所用材料的依赖性。我们发现，骨长入本身会大幅降低骨的近端负荷。在典型的骨长入情况下，与无骨长入时相比，作用于骨近端的轴向和扭转载荷降低了多达两倍；骨近端的弯曲载荷也降低了。假体疲劳骨折风险对骨长入的发展不敏感。然而，假体疲劳骨折风险会随着假体和骨膜骨直径的减小以及假体模量的增加而增加。骨折的最大风险出现在将小直径钴铬合金假体植入小直径骨的活跃患者中。
