Anderson Orthopaedic Research Institute, PO Box 7088, Alexandria, VA 22307, USA.
Clin Orthop Relat Res. 2013 Jan;471(1):86-93. doi: 10.1007/s11999-012-2513-2.
Wear of total knee polyethylene has been quantified gravimetrically with thickness measurements and evaluation of surface wear modes. However, these techniques do not localize volumetric wear.
QUESTIONS/PURPOSES: We used micro-CT scans of retrieved total knee liners and unworn, new liners to determine the volume and location of wear.
We retrieved 12 fixed and 12 rotating-platform bearings after a mean 52 months of use. Inserts were weighed and thickness was measured. Micro-CT scans of retrieved and matched new liners were superimposed to compare the location and magnitude of wear.
The average total wear was 254 ± 248 mm(3). The average wear rate was 58 ± 41 mm(3)/year. Wear was 69% of penetration, demonstrating the contribution of deformation to knee wear. Rotating-platform wear rate was 43 ± 25 mm(3)/year and the fixed-bearing rate was 74 ± 49 mm(3)/year. Five percent of the rotating-platform wear rate came from the backside compared with 14% of the fixed-bearing wear rate.
Micro-CT can determine the volume and location of wear of retrieved tibial liners. Because the magnitude of the manufacturing tolerances was approximately half the magnitude of the total wear on average, accounting for the potential influence of tolerances is important to accurately measure volumetric wear if the unworn (preimplantation) geometry of the insert is unknown. Without accounting for tolerances, this technique may not be applicable for retrievals with a short followup that have low wear. However, application of micro-CT could be of value in determining the exact location of wear in knee simulator studies in which the same insert is measured repeatedly and manufacturing tolerances are not a concern.
全膝关节聚乙烯磨损已通过厚度测量和表面磨损模式评估进行了定量重力测量。然而，这些技术无法定位体积磨损。
问题/目的：我们使用回收的全膝关节衬垫和未使用的新衬垫的微 CT 扫描来确定磨损的体积和位置。
我们在平均使用 52 个月后回收了 12 个固定和 12 个旋转平台轴承。对插入物进行称重并测量厚度。将回收的和匹配的新衬垫的微 CT 扫描叠加，以比较磨损的位置和程度。
平均总磨损量为 254±248mm(3)。平均磨损率为 58±41mm(3)/年。磨损量为穿透深度的 69%，表明变形对膝关节磨损的贡献。旋转平台的磨损率为 43±25mm(3)/年，固定轴承的磨损率为 74±49mm(3)/年。与固定轴承的磨损率的 14%相比，旋转平台的磨损率有 5%来自背面。
微 CT 可以确定回收胫骨衬垫的体积和位置。由于制造公差的幅度平均约为总磨损量的一半，如果不知道插入物的未磨损（植入前）几何形状，则考虑公差的潜在影响对于准确测量体积磨损很重要。如果不考虑公差，对于随访时间短且磨损量低的回收物，该技术可能不适用。然而，微 CT 的应用可能对确定膝关节模拟器研究中磨损的确切位置具有价值，在该研究中，相同的插入物被重复测量，并且制造公差不是问题。
