Department of Orthopaedics, University of Utah, Salt Lake City, Utah.
Department of Bioengineering, University of Utah, Salt Lake City, Utah.
J Orthop Res. 2020 Jul;38(7):1477-1485. doi: 10.1002/jor.24701. Epub 2020 Apr 30.
Pelvic sagittal inclination (PSI) is often evaluated in patients with hip pathology using lateral radiographs. However, it would be useful if PSI could be predicted from an anteroposterior radiograph since this film is ubiquitous in the evaluation of hip pathology. Herein, computer-modeling was applied to predict PSI from radiographic measurements assessed in the anteroposterior plane. Three-dimensional surface models of the pelvis, femur, and sacrum were reconstructed from computed tomography images of 50 women with hip dysplasia. This study cohort was selected as changes in PSI alter femoral head coverage, which is relevant to the diagnosis and treatment of hip dysplasia, a known cause of hip osteoarthritis. Five radiographic parameters commonly used to independently estimate PSI were evaluated after bone surfaces were projected to an anteroposterior plane, including the symphysis to sacrococcygeal joint distance (S-S distance), the pelvic foramen aspect ratio (PF ratio), the distance between the symphysis and a line connecting the femoral head centers (S-H distance), the sacro-femoral-pubic angle (SFP angle), and the pelvic vertical ratio (PVR). Regression models determined the ability of these parameters to predict PSI from -20° to 20° at 1° increment. All five parameters showed a strong correlation with the PSI (all r > 0.9). From the regression models, PSI was estimated with a median (maximum) absolute error of 3.6° (18.4°), 3.8° (17.7°), 5.2° (17.9°), 5.8° (28.8°), and 3.2° (23.5°) for the S-S distance, PF ratio, S-H distance, SFP angle, and PVR, respectively. The regression model for S-S distance had a mean slope of 2.18 that ranged from 1.98 to 2.41 when the sacrococcygeal joint was located superior to the symphysis. Results indicated that substantial errors occur when estimating the actual value of PSI from an anteroposterior radiograph. However, the change in PSI could be estimated from the S-S distance, which may aid surgeons to successfully increase head coverage through periacetabular osteotomy and to locate the acetabular cup in a functional position for total hip arthroplasty.
骨盆矢状倾斜度（PSI）常通过侧位 X 线片评估髋关节疾病患者。然而，如果 PSI 可以通过前后位 X 线片预测，那将非常有用，因为前后位 X 线片在髋关节疾病的评估中无处不在。在此，我们通过计算机建模应用于从前后位平面的放射学测量值预测 PSI。从 50 例髋关节发育不良女性的 CT 图像重建骨盆、股骨和骶骨的三维表面模型。本研究队列选择是因为 PSI 的变化会改变股骨头覆盖，这与髋关节发育不良的诊断和治疗相关，髋关节发育不良是髋关节骨关节炎的已知病因。评估了 5 个常用于独立估计 PSI 的放射学参数，这些参数在将骨表面投影到前后位平面后进行评估，包括耻骨联合至尾骨关节距离（S-S 距离）、骨盆入口面比（PF 比）、耻骨联合与连接股骨头中心的线之间的距离（S-H 距离）、骶股耻骨角（SFP 角）和骨盆垂直比（PVR）。回归模型确定了这些参数在 -20°至 20°之间以 1°递增预测 PSI 的能力。所有 5 个参数与 PSI 均具有很强的相关性（所有 r>0.9）。从回归模型来看，S-S 距离、PF 比、S-H 距离、SFP 角和 PVR 分别预测 PSI 的中位数（最大）绝对误差为 3.6°（18.4°）、3.8°（17.7°）、5.2°（17.9°）、5.8°（28.8°）和 3.2°（23.5°）。S-S 距离的回归模型平均斜率为 2.18，当尾骨关节位于耻骨联合上方时，斜率范围为 1.98 至 2.41。结果表明，从前后位 X 线片估计 PSI 的实际值会产生较大误差。然而，PS 变化可以通过 S-S 距离来估计，这可能有助于外科医生通过髋臼周围截骨术成功增加股骨头覆盖，并将髋臼杯定位在全髋关节置换术中的功能位置。
