Uemura Keisuke, Takao Masaki, Otake Yoshito, Koyama Koki, Yokota Futoshi, Hamada Hidetoshi, Sakai Takashi, Sato Yoshinobu, Sugano Nobuhiko
1 Department of Orthopaedic Medical Engineering, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
2 Graduate School of Information Science, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
J Orthop Surg (Hong Kong). 2019 Jan-Apr;27(1):2309499019828515. doi: 10.1177/2309499019828515.
Pelvic position on the sagittal plane is usually evaluated with the pelvic sagittal inclination (PSI) angle from a single radiograph. However, the reproducibility of pelvic positioning has not been investigated, and thus, the validity of measuring the PSI from a single film/time point is not understood. Herein, the reproducibility of a patient's pelvic positions in supine and standing postures was analyzed.
A total of 34 patients who underwent either a pelvic osteotomy or total hip arthroplasty were enrolled in this study. Preoperative radiographs in both supine and standing postures were acquired twice (first X-ray and second X-ray) within 6 months; preoperative computed tomography (CT) images of the full pelvis were also acquired in a supine posture (preop-CT). To eliminate measurement variability, each PSI was automatically measured from radiographs and CT images through the use of CT segmentation and landmark localization followed by intensity-based 2D-3D registration. The absolute difference of PSI among each image was calculated and the intra-class correlation coefficient (ICC) in each posture was also analyzed.
The median absolute differences of PSI in the supine posture were 1.3° between the first and second X-rays, 1.2° between the first X-ray and preop-CT, and 1.3° between the second X-ray and preop-CT. The median absolute difference of PSI in the standing posture was 1.5°. The ICC was 0.965 (95% CI: 0.939-0.981) in supine and 0.977 (95% CI: 0.954-0.988) during standing.
Pelvic positions in supine and standing postures are reproducible. Thus, measuring the PSI from a single radiograph is reliable.
骨盆矢状面位置通常通过单张X线片上的骨盆矢状倾斜（PSI）角进行评估。然而，骨盆定位的可重复性尚未得到研究，因此，从单张胶片/时间点测量PSI的有效性尚不清楚。在此，分析了患者仰卧位和站立位时骨盆位置的可重复性。
本研究共纳入34例行骨盆截骨术或全髋关节置换术的患者。在6个月内对仰卧位和站立位的术前X线片进行两次拍摄（第一次X线片和第二次X线片）；还获取了仰卧位的全骨盆术前计算机断层扫描（CT）图像（术前CT）。为消除测量变异性，通过使用CT分割和地标定位，然后基于强度的二维-三维配准，从X线片和CT图像中自动测量每个PSI。计算每张图像之间PSI的绝对差值，并分析每种姿势下的组内相关系数（ICC）。
仰卧位时，第一次和第二次X线片之间PSI的中位绝对差值为1.3°，第一次X线片与术前CT之间为1.2°，第二次X线片与术前CT之间为1.3°。站立位时PSI的中位绝对差值为1.5°。仰卧位时ICC为0.965（95%CI：0.939-0.981），站立位时为0.977（95%CI：0.954-0.988）。
仰卧位和站立位时的骨盆位置具有可重复性。因此，从单张X线片测量PSI是可靠的。
