Teeter Matthew G, Milner Jaques S, MacDonald Steven J, Naudie Douglas D R
Division of Orthopaedic Surgery, London Health Sciences Centre, London, ON, Canada.
Proc Inst Mech Eng H. 2013 Aug;227(8):884-9. doi: 10.1177/0954411913486755. Epub 2013 Apr 26.
To perform wear measurements on retrieved joint replacement implants, a reference geometry of the implant's original state is required. Since implants are rarely individually scanned before implantation, a different, new implant of the same kind and size is frequently used. However, due to manufacturing variability, errors may be introduced into these measurements, as the dimensions between the retrieved and reference components may not be exactly the same. The hypothesis of this study was that new polyethylene tibial inserts from different manufacturing lots would demonstrate greater variability than those from the same lot. In total, 12 new tibial inserts of the same model and size were obtained, 5 from the same lot and the remainder from different lots. The geometry of each tibial insert was obtained using microcomputed tomography. Measurements of tibial insert volume, thickness, and three-dimensional surface deviations were obtained and compared between tibial inserts from the same and different manufacturing lots. Greater variability was found for the tibial inserts from different manufacturing lots for all types of measurements, including a fourfold difference in volume variability (p < 0.001) and a maximum of 0.21 mm difference in thickness (p < 0.001). Investigators should be aware of this potential confounding error and take steps to minimize it, such as by averaging together the geometries of multiple new components from different manufacturing lots for use as the reference geometry.
为了对取出的关节置换植入物进行磨损测量，需要植入物原始状态的参考几何形状。由于植入物在植入前很少进行单独扫描，通常会使用同种型号和尺寸的不同新植入物。然而，由于制造差异，这些测量可能会引入误差，因为取出的部件与参考部件之间的尺寸可能不完全相同。本研究的假设是，来自不同生产批次的新型聚乙烯胫骨插入物比来自同一批次的具有更大的变异性。总共获得了12个相同型号和尺寸的新胫骨插入物，其中5个来自同一批次，其余来自不同批次。使用微型计算机断层扫描获取每个胫骨插入物的几何形状。获取并比较了来自相同和不同生产批次的胫骨插入物的体积、厚度和三维表面偏差测量值。在所有类型的测量中，发现来自不同生产批次的胫骨插入物具有更大的变异性，包括体积变异性的四倍差异（p < 0.001）和厚度最大0.21毫米的差异（p < 0.001）。研究人员应意识到这种潜在的混杂误差，并采取措施将其最小化，例如将来自不同生产批次的多个新部件的几何形状平均起来用作参考几何形状。
