Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014, Bern, Switzerland.
Int J Comput Assist Radiol Surg. 2012 Mar;7(2):225-31. doi: 10.1007/s11548-011-0644-7. Epub 2011 Jul 27.
The aim of this study was to validate the accuracy and reproducibility of a statistical shape model-based 2D/3D reconstruction method for determining cup orientation after total hip arthroplasty. With a statistical shape model, this method allows reconstructing a patient-specific 3D-model of the pelvis from a standard AP X-ray radiograph. Cup orientation (inclination and anteversion) is then calculated with respect to the anterior pelvic plane that is derived from the reconstructed model.
The validation study was conducted retrospectively on datasets of 29 patients (31 hips). Among them, there were 15 men (15 hips) and 14 women (16 hips). The average age of the patients was 69.4±8.5 (49-82) years. Each dataset has one postoperative X-ray radiograph and one postoperative CT scan. The postoperative CT scan for each patient was used to establish the ground truth for the cup orientation. The cup anteversion and inclination that were calculated from the 2D/3D reconstruction method were compared to the associated ground truth. To validate reproducibility and reliability, two observers performed measurements for each dataset twice in order to measure the reproducibility and the reliability of the 2D/3D reconstruction method.
Our validation study demonstrated a mean accuracy of 0.4 ± 1.8° (-2.6° to 3.3°) for inclination and a mean accuracy of 0.6±1.5° (-2.0° to 3.9°) for anteversion. Through the Bland-Altman analysis, no systematic errors in accuracy were detected. The method showed very good consistency for both parameters.
Our validation results demonstrate that the statistical shape model-based 2D/3D reconstruction-based method is an accurate, consistent, and reproducible technique to measure cup orientation from postoperative X-ray radiographs. The best results were achieved with radiographs including the bilateral anterior superior iliac spines and the cranial part of non-fractured pelvises.
本研究旨在验证一种基于统计形状模型的 2D/3D 重建方法在全髋关节置换术后确定杯倾斜度和前倾角的准确性和可重复性。通过统计形状模型，该方法允许从标准的 AP X 射线射线照相术中重建患者特定的骨盆 3D 模型。然后，根据从重建模型中得出的前骨盆平面来计算杯倾斜度（倾斜和前倾角）。
该验证研究是回顾性地对 29 名患者（31 髋）的数据集进行的。其中，有 15 名男性（15 髋）和 14 名女性（16 髋）。患者的平均年龄为 69.4±8.5（49-82）岁。每个数据集都有一张术后 X 射线射线照相和一张术后 CT 扫描。每位患者的术后 CT 扫描被用于确定杯倾斜度的基准。从 2D/3D 重建方法中计算出的杯前倾角和倾斜度与相关的基准进行了比较。为了验证可重复性和可靠性，两位观察者对每个数据集进行了两次测量，以测量 2D/3D 重建方法的可重复性和可靠性。
我们的验证研究表明，倾斜的平均准确度为 0.4 ± 1.8°（-2.6°至 3.3°），前倾角的平均准确度为 0.6±1.5°（-2.0°至 3.9°）。通过 Bland-Altman 分析，未检测到准确性的系统误差。该方法对这两个参数均表现出很好的一致性。
我们的验证结果表明，基于统计形状模型的 2D/3D 重建方法是一种准确、一致且可重复的技术，可从术后 X 射线射线照相术中测量杯倾斜度。在包括双侧前上髂棘和未骨折骨盆的头部分的射线照相术中获得了最佳结果。
