Rapperport D J, Carter D R, Schurman D J
Veterans Administration RRanD Center, Palo Alto, California.
J Orthop Res. 1987;5(4):548-61. doi: 10.1002/jor.1100050410.
Two-dimensional linear and contact finite element analyses were conducted of total hip arthroplasty using metal-backed, porous ingrowth acetabular components. The stress transmission characteristics from the component to the surrounding bone were given special attention. Resultant loads of 20 and 40 degrees medial of vertical were studied, and the influence of adding a metal flange to the rim of the cup was evaluated. The results indicated that when a conventional metal-backed component (without a flange) is initially implanted and subjected to normal loading, these components may experience distraction between the component and the surrounding bone at inferior sites. Compressive stresses in the superior dome cancellous bone, however, will be substantial. If complete porous ingrowth is achieved, the superior dome compressive stresses will be reduced and substantial shear stresses created. In addition, high local bone stresses were found at the component rim. If bone ingrowth is achieved only in specific locations, stress transmission will be dictated by those locations and may differ markedly from the case of complete bone ingrowth. In the event that no porous ingrowth is achieved and a fibrous layer forms around the component, the interface stresses will be similar to those calculated for the natural hip. The addition of a flange to the rim of the cup will reduce the magnitude of the radial stresses transmitted to the cancellous bone superiorly and medially by directly transferring some of the load to the lateral wall of the pelvis. The flange will also help to relieve the high local stresses that are found at the component rim.
对使用金属背衬、多孔长入型髋臼组件的全髋关节置换术进行了二维线性和接触有限元分析。特别关注了组件到周围骨骼的应力传递特性。研究了垂直方向内侧20度和40度的合成载荷，并评估了在髋臼杯边缘添加金属法兰的影响。结果表明，当最初植入传统的金属背衬组件（无法兰）并承受正常载荷时，这些组件在下侧部位可能会在组件与周围骨骼之间出现分离。然而，上穹窿松质骨中的压应力将很大。如果实现完全的多孔长入，上穹窿的压应力将降低，并产生大量剪应力。此外，在组件边缘发现了高局部骨应力。如果仅在特定位置实现骨长入，应力传递将由这些位置决定，可能与完全骨长入的情况有显著差异。如果未实现多孔长入且在组件周围形成纤维层，界面应力将与天然髋关节计算的应力相似。在髋臼杯边缘添加法兰将通过直接将部分载荷传递到骨盆侧壁来降低向上和向内传递到松质骨的径向应力大小。法兰还将有助于缓解在组件边缘发现的高局部应力。
