Department of Orthopaedic Surgery, Graduate School, College of Medicine, Kyung Hee University, 23, Kyungheedae-ro, Dongdaemun-gu, Seoul, 130-872, South Korea.
BMC Musculoskelet Disord. 2022 Feb 2;23(1):110. doi: 10.1186/s12891-022-05063-9.
Pelvic incidence (PI) is used as a key parameter in surgical correction of adult spinal deformity (ASD). However, reflecting the exact center or inclination of the three-dimensional anatomical structures on the two-dimensional (2D) sagittal radiographs is limited, resulting in measurement errors. Therefore, we evaluated whether there is a change in PI measurement according to the actual rotation of the pelvis, and conducted a study on a more accurate method for PI measurement using 2D sagittal radiographs.
From 2014 to 2015, the data of 30 patients who visited our outpatient clinic were analyzed retrospectively. CT scans including those of the lower lumbar spine, pelvis, and both femurs in the DICOM format were imported to Mimics Research 17.0 (Materialise NV, Belgium), SolidWorks (Dassault systems, France), and AutoCAD 2014 (AUTODESK, US). The changes in PI according to vertical and horizontal pelvic rotations were evaluated.
The average PIs according to the horizontal pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 48.7°, 48.3°, 47.8°, 46.9°, 45.6°, 44.0°, 42.2°, and 39.9°, respectively. The PI with an acceptable error of 6° on radiographs was 35° in the horizontal pelvic rotation. The average PIs according to the vertical pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 49.0°, 49.5°, 50.2°, 51.3°, 52.7°, 54.4°, 56.6°, and 59.4°, respectively. The PI with an acceptable error of 6° on radiographs was 30° in the vertical pelvic rotation.
This study revealed that the PI value could differ from the actual anatomical value due to the horizontal and vertical rotation of the pelvis while acquiring the radiograph. Regarding whole-spine lateral radiographs, errors in PI measurement may occur due to pelvic rotation or nonvertical projection of X-rays. In the standing pelvic lateral radiographs, ensuring superposition of the femoral heads at the center and obtaining the straight sacral endplate by referring to CT or magnetic resonance imaging would be a more accurate measurement method to define PI.
骨盆入射角（PI）被用作矫正成人脊柱畸形（ASD）的关键参数。然而，在二维（2D）矢状位 X 光片上反映三维解剖结构的真实中心或倾斜度是有限的，这会导致测量误差。因此，我们评估了骨盆实际旋转时 PI 测量值是否会发生变化，并对使用 2D 矢状位 X 光片更准确地测量 PI 进行了研究。
回顾性分析 2014 年至 2015 年期间我院门诊患者的 30 例患者的数据。以 DICOM 格式导入包括下腰椎、骨盆和双侧股骨的 CT 扫描图像至 Mimics Research 17.0（Materialise NV，比利时）、SolidWorks（Dassault systems，法国）和 AutoCAD 2014（AUTODESK，美国）。评估骨盆垂直和水平旋转时 PI 的变化。
AutoCAD 上根据骨盆水平旋转测量的平均 PI 值分别为 0°、5°、10°、15°、20°、25°、30°、35°和 40°时为 48.8°、48.7°、48.3°、47.8°、46.9°、45.6°、44.0°、42.2°和 39.9°。X 光片上可接受误差为 6°的 PI 值为水平骨盆旋转时的 35°。AutoCAD 上根据骨盆垂直旋转测量的平均 PI 值分别为 0°、5°、10°、15°、20°、25°、30°、35°和 40°时为 48.8°、49.0°、49.5°、50.2°、51.3°、52.7°、54.4°、56.6°和 59.4°。X 光片上可接受误差为 6°的 PI 值为垂直骨盆旋转时的 30°。
本研究表明，在获取 X 光片时，由于骨盆的水平和垂直旋转，PI 值可能与实际解剖值不同。对于全脊柱侧位 X 光片，由于骨盆旋转或 X 射线非垂直投影，PI 测量可能会出现误差。在站立骨盆侧位 X 光片上，通过参考 CT 或磁共振成像使股骨头在中心重合并获得直的骶骨终板，将是一种更准确的测量 PI 的方法。
