Department of Orthopaedic and Trauma Surgery, University Hospital of Cologne, Joseph-Stelzmann-Str. 9, 50924, Cologne, Germany.
Institute of Diagnostic and Interventional Radiology, University Hospital of Cologne, Cologne, Germany.
Int Orthop. 2019 Aug;43(8):1799-1805. doi: 10.1007/s00264-018-4120-7. Epub 2018 Aug 21.
Digital templating for total joint replacement is the current standard. For image calibration, external calibration markers (ECM) are used. However, there are concerns regarding the precision of the method. This study aimed to identify the direct influence of calibration errors on digital templating.
A retrospective analysis of 100 post-operative radiographs with unilateral total hip arthroplasty was performed. The magnification factor of the ECM and of the internal prosthetic femoral head (ICM) as a reference value was calculated for each radiograph. Two blinded observers performed templating of the contralateral hip using a randomized list for all radiographs and both markers. The component size templated by the ECM magnification was compared to the reference by the ICM magnification.
Mean magnification factors of ICM and ECM differed significantly (p = 0.006). The absolute difference was 5.2% (range 0.0-23.3%, SD 4.8%). Templating of the acetabular or the femoral component showed no significant differences (p = 0.120, p = 0.599). Differences of more than one size were found in 26% of the acetabular components and 14% of the femoral components and differences over two sizes in 10% respectively 3%. Correlation coefficients for magnification error and size differences of acetabular components were - 0.645 (p < 0.001) and for the femoral component - 0.607 (p < 0.001).
The calibration error of external calibration markers in digital templating for hip replacement influences component sizes significantly. Thus, correct positioning of ECM is of utmost importance.
数字模板制作在全关节置换术中是目前的标准。对于图像校准，使用外部校准标记（ECM）。然而，人们对该方法的精度存在担忧。本研究旨在确定校准误差对数字模板制作的直接影响。
对 100 例单侧全髋关节置换术后的术后 X 光片进行回顾性分析。计算每张 X 光片上 ECM 和内部假体股骨头（ICM）的放大系数作为参考值。两名盲法观察者使用所有 X 光片和两种标记物的随机列表对对侧髋关节进行模板制作。通过 ICM 放大倍数来比较 ECM 放大倍数所确定的组件尺寸与参考值。
ICM 和 ECM 的平均放大系数差异有统计学意义（p=0.006）。绝对值差异为 5.2%（范围 0.0-23.3%，SD 4.8%）。髋臼或股骨组件的模板制作没有显著差异（p=0.120，p=0.599）。髋臼组件中有 26%、股骨组件中有 14%的组件尺寸差异超过一个尺寸，分别有 10%和 3%的组件尺寸差异超过两个尺寸。髋臼组件放大误差和尺寸差异的相关系数为-0.645（p<0.001），股骨组件为-0.607（p<0.001）。
髋关节置换术数字模板制作中外置校准标记的校准误差会显著影响组件尺寸。因此，正确放置 ECM 非常重要。
