Moore K D, Barrack R L, Sychterz C J, Sawhney J, Yang A M, Engh C A
Anderson Orthopaedic Research Institute, Alexandria, Virginia 22307, USA.
J Bone Joint Surg Am. 2000 Jan;82(1):62-9.
In most radiographic studies of polyethylene wear, investigators have used routine annual radiographs made with the patient in the supine position in order to measure penetration by the femoral head into the polyethylene liner. However, researchers have begun to question the effect of weight-bearing on the position of the head within the acetabular cup and, consequently, the effect of weight-bearing on measurements of penetration by the head. The purpose of the current study was to determine the effect of weight-bearing on the two-dimensional radiographic position of the femoral head within the acetabular cup.
Thirty-seven patients (forty-seven hips) who had had a total hip arthroplasty had radiographs made at one of two separate institutions. A set of anteroposterior radiographs was made for each patient: one radiograph was made with the patient supine and one was made with the patient upright bearing full weight on the replaced hip. At one of the institutions, a third anteroposterior radiograph was made with the patient in the same upright position but not bearing weight on the replaced hip. All measurements of the two-dimensional position of the head were performed by a single observer with use of a previously published computerized measurement system.
Data from both institutions revealed that measurements of the position of the head on radiographs made with the patient supine were strongly and significantly correlated with measurements of the position of the head on radiographs made with the patient bearing weight (r2>0.93, p<0.001 for both regressions). Examination of the differences between the measurements revealed no bias for one set of measurements to consistently underestimate or overestimate the values derived with use of the other method. Moreover, we found a nearly perfect relationship between the measurements of the position of the head on radiographs made with the patient standing and bearing weight and those on radiographs made with the patient standing but not bearing weight (r2 = 0.97, p<0.001, slope = 0.99, intercept = 0.02 millimeter).
On the basis of these findings, there is no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner.
在大多数关于聚乙烯磨损的放射学研究中，研究人员使用患者仰卧位时每年常规拍摄的X线片来测量股骨头向聚乙烯内衬的穿透情况。然而，研究人员开始质疑负重对股骨头在髋臼杯内位置的影响，进而质疑负重对股骨头穿透测量的影响。本研究的目的是确定负重对股骨头在髋臼杯内二维放射学位置的影响。
37例（47髋）接受全髋关节置换术的患者在两个不同机构之一拍摄X线片。为每位患者拍摄一组前后位X线片：一张是患者仰卧位时拍摄，另一张是患者站立且置换髋关节完全负重时拍摄。在其中一个机构，还为患者拍摄了第三张前后位X线片，患者站立姿势相同但置换髋关节不负重。股骨头二维位置的所有测量均由一名观察者使用先前发表的计算机测量系统进行。
两个机构的数据均显示，患者仰卧位时拍摄的X线片上股骨头位置的测量值与患者负重时拍摄的X线片上股骨头位置的测量值呈强且显著的相关性（两个回归分析的r2>0.93，p<0.001）。对测量值差异的检查显示，一组测量值不存在始终低估或高估另一组测量值的偏差。此外，我们发现患者站立且负重时拍摄的X线片上股骨头位置的测量值与患者站立但不负重时拍摄的X线片上股骨头位置的测量值之间存在近乎完美的关系（r2 = 0.97，p<0.001，斜率 = 0.99，截距 = 0.02毫米）。
基于这些发现，没有证据表明必须在患者负重时拍摄X线片才能准确测量股骨头在聚乙烯内衬内的位置。
