Bragdon Charles R, Malchau Henrik, Yuan Xunhua, Perinchief Rebecca, Kärrholm Johan, Börlin Niclas, Estok Daniel M, Harris William H
Department of Orthopaedic Surgery of Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
J Orthop Res. 2002 Jul;20(4):688-95. doi: 10.1016/S0736-0266(01)00171-1.
The purpose of this study was to develop and test a phantom model based on actual total hip replacement (THR) components to simulate the true penetration of the femoral head resulting from polyethylene wear. This model was used to study both the accuracy and the precision of radiostereometric analysis, RSA, in measuring wear. We also used this model to evaluate optimum tantalum bead configuration for this particular cup design when used in a clinical setting. A physical model of a total hip replacement (a phantom) was constructed which could simulate progressive, three-dimensional (3-D) penetration of the femoral head into the polyethylene component of a THR. Using a coordinate measuring machine (CMM) the positioning of the femoral head using the phantom was measured to be accurate to within 7 microm. The accuracy and precision of an RSA analysis system was determined from five repeat examinations of the phantom using various experimental set-ups of the phantom. The accuracy of the radiostereometric analysis, in this optimal experimental set-up studied was 33 microm for the medial direction, 22 microm for the superior direction, 86 microm for the posterior direction and 55 microm for the resultant 3-D vector length. The corresponding precision at the 95% confidence interval of the test results for repositioning the phantom five times, measured 8.4 microm for the medial direction, 5.5 microm for the superior direction, 16.0 microm for the posterior direction, and 13.5 microm for the resultant 3-D vector length. This in vitro model is proposed as a useful tool for developing a standard for the evaluation of radiostereometric and other radiographic methods used to measure in vivo wear.
本研究的目的是开发并测试一种基于实际全髋关节置换（THR）组件的体模模型，以模拟因聚乙烯磨损导致的股骨头真实穿透情况。该模型用于研究放射立体测量分析（RSA）在测量磨损方面的准确性和精密度。我们还使用此模型评估在临床环境中使用这种特定髋臼杯设计时钽珠的最佳配置。构建了一个全髋关节置换的物理模型（体模），它可以模拟股骨头向THR聚乙烯组件的渐进性三维（3-D）穿透。使用坐标测量机（CMM）测量，使用该体模时股骨头的定位精度在7微米以内。通过对体模进行各种实验设置后对其进行五次重复检查，确定了RSA分析系统的准确性和精密度。在本研究的这种最佳实验设置中，放射立体测量分析的准确性在内侧方向为33微米，在上方方向为22微米，在后方方向为86微米，在合成3-D向量长度方向为55微米。在对体模进行五次重新定位的测试结果的95%置信区间下，相应的精密度在内侧方向为8.4微米，在上方方向为5.5微米，在后方方向为16.0微米，在合成3-D向量长度方向为13.5微米。该体外模型被提议作为一种有用的工具，用于制定评估用于测量体内磨损的放射立体测量及其他射线照相方法的标准。
