Schwarz T, Weber M, Wörner M, Renkawitz T, Grifka J, Craiovan B
Department of Orthopedic Surgery, Regensburg University Medical Center, Kaiser-Karl-V.-Allee 3, 93077, Bad Abbach, Germany.
Int J Comput Assist Radiol Surg. 2017 May;12(5):829-837. doi: 10.1007/s11548-016-1489-x. Epub 2016 Oct 6.
Accurate assessment of cup orientation on postoperative radiographs is essential for evaluating outcome after THA. However, accuracy is impeded by the deviation of the central X-ray beam in relation to the cup and the impossibility of measuring retroversion on standard pelvic radiographs.
In an experimental trial, we built an artificial cup holder enabling the setting of different angles of anatomical anteversion and inclination. Twelve different cup orientations were investigated by three examiners. After comparing the two methods for radiographic measurement of the cup position developed by Lewinnek and Widmer, we showed how to differentiate between anteversion and retroversion in each cup position by using a second plane. To show the effect of the central beam offset on the cup, we X-rayed a defined cup position using a multidirectional central beam offset. According to Murray's definition of anteversion and inclination, we created a novel corrective procedure to balance measurement errors caused by deviation of the central beam.
Measurement of the 12 different cup positions with the Lewinnek's method yielded a mean deviation of [Formula: see text] (95 % CI 1.3-2.3) from the original cup anteversion. The respective deviation with the Widmer/Liaw's method was [Formula: see text] (95 % CI 2.4-4.0). In each case, retroversion could be differentiated from anteversion with a second radiograph. Because of the multidirectional central beam offset ([Formula: see text] cm) from the acetabular cup in the cup holder ([Formula: see text] anteversion and [Formula: see text] inclination), the mean absolute difference for anteversion was [Formula: see text] (range [Formula: see text] to [Formula: see text] and [Formula: see text] (range [Formula: see text] to [Formula: see text] for inclination. The application of our novel mathematical correction of the central beam offset reduced deviation to a mean difference of [Formula: see text] for anteversion and [Formula: see text] for inclination.
This novel calculation for central beam offset correction enables highly accurate measurement of the cup position.
准确评估术后X线片上髋臼杯的方向对于评估全髋关节置换术（THA）后的疗效至关重要。然而，由于中心X线束相对于髋臼杯的偏差以及在标准骨盆X线片上无法测量髋臼后倾，测量的准确性受到了阻碍。
在一项实验性试验中，我们制作了一个人工髋臼杯固定器，能够设置不同的解剖学前倾角和倾斜角。三名检查者对12种不同的髋臼杯方向进行了研究。在比较了Lewinnek和Widmer提出的两种用于X线片测量髋臼杯位置的方法后，我们展示了如何通过使用第二个平面在每个髋臼杯位置区分前倾角和后倾角。为了显示中心束偏移对髋臼杯的影响，我们使用多方向中心束偏移对一个定义好的髋臼杯位置进行了X线检查。根据Murray对前倾角和倾斜角的定义，我们创建了一种新的校正程序，以平衡由中心束偏差引起的测量误差。
使用Lewinnek方法测量12种不同的髋臼杯位置时，与原始髋臼杯前倾角的平均偏差为[公式：见原文]（95%可信区间1.3 - 2.3）。使用Widmer/Liaw方法时的相应偏差为[公式：见原文]（95%可信区间2.4 - 4.0）。在每种情况下，通过第二张X线片都可以区分后倾角和前倾角。由于在髋臼杯固定器中中心束相对于髋臼杯的多方向偏移（[公式：见原文]厘米）（[公式：见原文]前倾角和[公式：见原文]倾斜角），前倾角的平均绝对差值为[公式：见原文]（范围从[公式：见原文]到[公式：见原文]），倾斜角的平均绝对差值为[公式：见原文]（范围从[公式：见原文]到[公式：见原文]）。应用我们新的中心束偏移数学校正方法后，前倾角的偏差降低至平均差值[公式：见原文]，倾斜角的偏差降低至平均差值[公式：见原文]。
这种用于中心束偏移校正的新计算方法能够实现对髋臼杯位置的高精度测量。
