VALIDATION OF MEASURING PI USING CT AND A COMPARISON WITH WHOLE SPINE AND LUMBOSACRAL X-RAYS

ABSTRACT Objective: The objective of this study is to describe a new, extremely simple method for measuring pelvic incidence (PI) using computed tomography (CT) and to compare those measurements with measurements derived from whole spine and lumbosacral X-rays in a Brazilian population. Methods: Patients who had whole spine and lumbosacral X-rays and whole abdomen, pelvis, or lumbar spine CT performed within a period of less than three months were selected. Image overlay was used to measure PI from the CT. The PI was calculated by two independent examiners, and the PI for each exam was calculated twice, with an interval of two months between the assessments. The intra- and interexaminer reliability and reproducibility were evaluatedusing the intraclass correlation coefficient (ICC) and the repeatability coefficient, considering a 95% confidence interval. Results: Fifty-five patients of both sexes with a mean age of 58.7 years (±19) were analyzed. The mean PI angles in the analyses of both examiners at both evaluations were 54.85° (±13.73) for the whole spine X-ray, 54.06° (±11.67) for the lumbosacral spine X-ray, and 49.96° (±9.85) for the CT. There was good intra- and interexaminer reliability and reproducibility. There was also high concordancewith the whole spine and lumbosacral X-rays. Conclusion: CT is a reliable and reproducible alternative for measuring PI. Level of Evidence III; Prospective comparative.

摘要
目的：本研究旨在描述一种利用计算机断层扫描（computed tomography, CT）测量骨盆入射角（pelvic incidence, PI）的全新极简方法，并在巴西人群中将该方法所得测量结果与全脊柱及腰骶部X线摄影的测量结果进行对比。
方法：选取三个月内完成全脊柱及腰骶部X线摄影、全腹、骨盆或腰椎CT检查的患者作为研究对象。采用图像叠加法通过CT测量骨盆入射角。由两名独立检查者分别完成测量，每名检查者对每份病例均开展两次测量，两次测量间隔为两个月。以95%置信区间为基准，采用组内相关系数（intraclass correlation coefficient, ICC）及重复性系数评估检查者内与检查者间的信度与可重复性。
结果：本研究共纳入55名男女患者，平均年龄为58.7岁（±19）。两名检查者两次评估所得的全脊柱X线摄影骨盆入射角均值为54.85°（±13.73），腰骶部脊柱X线摄影为54.06°（±11.67），CT测量结果为49.96°（±9.85）。检查者内与检查者间均具有良好的信度与可重复性，且与全脊柱及腰骶部X线摄影结果具有高度一致性。
结论：CT是一种可靠且可重复的骨盆入射角测量替代方法。证据等级：Ⅲ级；前瞻性对照研究。