Ilchmann T, Reimold M, Müller-Schauenburg W
Department of Orthopaedics, Kantonsspital, Rheinstrasse 26, Liestal, Switzerland.
Med Eng Phys. 2008 Apr;30(3):373-9. doi: 10.1016/j.medengphy.2007.04.003. Epub 2007 Jun 13.
Various formulas have been proposed to calculate the volume of prosthetic wear from the penetration depth of the head as assessed on plain radiographs, based on idealized, three-dimensional geometrical models of a prosthetic hip. However, for most published formulas no (or no simple) derivation is available and not all of them are correct. We describe a simple geometrical model that allows for transparent derivation of equations for various components of prosthetic wear volume and compare the calculated volumes with those obtained from published equations. These components are: (1) a right generalized cylinder resulting from a linear shift of a half spherical part of the prosthetic head into the hemispherical cup, (2) an additional wedge that is "cut" from the cup and (3) the wear from an optional additional cylindrical portion of the cup. We emphasize that calculation of a three-dimensional wear volume from linear penetration depth should be based on a geometrical concept that is transparent and simple enough for clinical research, such as the one presented. The incorrect formula of Kabo et al. should be completely abandoned.
基于理想化的人工髋关节三维几何模型，人们提出了各种公式，用于根据X线平片评估的股骨头穿透深度来计算假体磨损量。然而，对于大多数已发表的公式，没有（或没有简单的）推导过程，而且并非所有公式都是正确的。我们描述了一个简单的几何模型，该模型允许透明地推导假体磨损体积各组成部分的方程，并将计算出的体积与从已发表方程中获得的体积进行比较。这些组成部分包括：（1）一个右广义圆柱体，它是由假体头部的半球形部分线性移入半球形髋臼而形成的；（2）从髋臼“切出”的一个额外楔形体；（3）髋臼可选额外圆柱形部分的磨损。我们强调，从线性穿透深度计算三维磨损体积应基于一个足够透明和简单的几何概念，以便用于临床研究，比如本文所提出的概念。Kabo等人的错误公式应完全摒弃。
