Jedenmalm Anneli, Noz Marilyn E, Olivecrona Henrik, Olivecrona Lotta, Stark Andre
Department of Fiber and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden.
Acta Orthop. 2008 Apr;79(2):218-24. doi: 10.1080/17453670710015003.
Polyethylene wear is an important cause of aseptic loosening in hip arthroplasty. Detection of significant wear usually happens late on, since available diagnostic techniques are either not sensitive enough or too complicated and expensive for routine use. This study evaluates a new approach for measurement of linear wear of metal-backed acetabular cups using CT as the intended clinically feasible method.
8 retrieved uncemented metal-backed acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral head into the cup was measured in the CT volumes using dedicated software. Landmark points were placed on the CT images of cup and head, and also on a reference plane in order to calculate the wear vector magnitude and angle to one of the axes. A coordinate-measuring machine was used to test the accuracy of the proposed CT method. For this purpose, the head diameters were also measured by both methods.
Accuracy of the CT method for linear wear measurements was 0.6 mm and wear vector angle was 27 degrees . No systematic difference was found between CT scans.
This study on explanted acetabular cups shows that CT is capable of reliable measurement of linear wear in acetabular cups at a clinically relevant level of accuracy. It was also possible to use the method for assessment of direction of wear.
聚乙烯磨损是髋关节置换术中无菌性松动的重要原因。由于现有的诊断技术要么不够灵敏，要么过于复杂昂贵而无法用于常规检查，因此通常在磨损情况较为严重时才能检测到明显的磨损。本研究评估一种使用CT测量金属背衬髋臼杯线性磨损的新方法，旨在使其成为临床上可行的方法。
对8个取出的非骨水泥型金属背衬髋臼杯进行体外CT扫描，扫描两次。使用专用软件在CT容积中测量股骨头进入髋臼杯的线性穿透深度。在髋臼杯和股骨头的CT图像上以及参考平面上设置标志点，以计算磨损向量的大小和相对于其中一个轴的角度。使用坐标测量机测试所提出的CT方法的准确性。为此，还通过两种方法测量了股骨头直径。
CT测量线性磨损的方法的准确度为0.6毫米，磨损向量角度为27度。两次CT扫描之间未发现系统差异。
对取出的髋臼杯的这项研究表明，CT能够在临床上相关的准确度水平上可靠地测量髋臼杯的线性磨损。使用该方法评估磨损方向也是可行的。
