BACKGROUND The severity of hip dysplasia is characterized by radiographic measurements that require user definition of the acetabular sourcil edge, a bony landmark for which the corresponding three-dimensional (3D) anatomy is not well defined in any imaging plane. QUESTIONS/PURPOSES To use digitally reconstructed radiographs to determine: (1) What 3D anatomy is contributing to the "acetabular sourcil" location used to make lateral center-edge angle (LCEA) and anterior center-edge angle (ACEA) measurements in standing AP and false-profile radiographic views, respectively? (2) How do intraobserver and interobserver agreement in LCEA and ACEA translate into agreement of the 3D anatomy being evaluated? (3) How distinct are regions around the acetabular rim circumference that are evaluated by LCEA and ACEA measurements on radiographs? METHODS Between January 2018 and May 2019, 72 patients were indicated for periacetabular osteotomy to treat hip dysplasia or acetabular retroversion at our institution. From these patients, a series of 10 patients were identified of the first 12 patients in 2018 who were treated with periacetabular osteotomy, excluding two with missing or low-quality clinical imaging. A second series of 10 patients was identified of the first 11 patients in 2019 who were treated with periacetabular osteotomy and concurrent hip arthroscopy, excluding one who was missing clinical imaging. Pelvis and femoral bone surface models were generated from CT scans of these two series of 10 patients. There were 15 female and five male patients, with a median patient age of 18 years (IQR 17 to 23 years), a preoperative LCEA of 22° (IQR 18° to 24°), and a preoperative ACEA of 23° (IQR 18° to 27°). Exclusion criteria included missing preoperative CT or standard clinical radiographic imaging or severe joint incongruity. To address our first study question, digitally reconstructed radiographs matching each patient's standing AP and false-profile clinical radiographs were created from the segmented CT volumes. A board-certified orthopaedic surgeon and three trained researchers measured LCEA and ACEA on the digitally reconstructed radiographs, and the selected sourcil points were projected back into coordinates in the 3D anatomic space. To address our second study question, intraobserver and interobserver agreement in radiographic coverage angles were related to variations in 3D coordinates of the selected bony anatomy. Lastly, to address our third study question, 3D locations around the acetabular rim identified as contributing to the lateral and anterior sourcil points were summarized across patients in a clockface coordinate system, and statistical analysis of the "time" separating the 3D acetabular contributions of the sourcil edges was performed. RESULTS The 3D anatomy contributing to the lateral sourcil was a variable length (27 mm [IQR 15 to 34 mm]) span of the laterosuperior acetabular edges, with contributions by the anterior inferior iliac spine in 35% (7 of 20) of hips. The anterior sourcil reflected a 28-mm (IQR 25 to 31 mm) span of bone from the medial ilium (posterior-medial to the anterior-inferior iliac spine and anterior-lateral to the arcuate line) to the anterior and lateral edges of the acetabulum. Interobserver variability was good for LCEA (intraclass correlation coefficient [ICC] 0.82 to 0.83) and moderate to good for ACEA (ICC 0.73 to 0.79), whereas the agreement in identified 3D sourcil locations varied widely (ICC 0.32 to 0.95). The acetabular edge of the 3D anatomy contributing to the anterior sourcil overlapped the circumferential range of the acetabular rim contributing to the lateral sourcil. CONCLUSION Projection of two-dimensional radiographic landmarks contributing to the diagnosis of structural hip deformity into 3D allowed for the identification of the overlapping bony anatomy contributing to radiographically visible anterior and lateral sourcil edges. CLINICAL RELEVANCE This work leveraging digitally reconstructed radiographs and 3D pelvis anatomy has found that bone outside the joint contributes to the radiographic appearance of the sourcil and may variably confound estimates of joint coverage. Furthermore, the substantial overlap between the acetabular bone contributing to measurement of the LCEA and ACEA would indicate that these angles measure similar acetabular deformity, and that additional measures are needed to assess anterior coverage independent of lateral coverage.

中文翻译：

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影像学上明显的髋臼酸标志是由骨盆的可比区域创建的，关节外骨不同程度地混淆了关节覆盖率的估计。


背景 髋关节发育不良的严重程度以放射学测量为特征，需要用户定义髋臼缘，这是一个骨标志，相应的三维 （3D） 解剖结构在任何成像平面上都没有明确定义。问题/目的 使用数字重建的 X 光片来确定： （1） 什么 3D 解剖结构有助于在站立 AP 和假轮廓射线照相视图中分别进行横向中心边缘角 （LCEA） 和前中心边缘角 （ACEA） 测量的“髋臼 sourcil”位置？（2） LCEA 和 ACEA 中的观察者内部和观察者间一致性如何转化为正在评估的 3D 解剖结构的一致性？（3） 通过 X 光片上的 LCEA 和 ACEA 测量评估的髋臼边缘周围区域有多大差异？方法 2018 年 1 月至 2019年5月期间，72 例患者在我们机构接受了髋臼周围截骨术治疗髋关节发育不良或髋臼后倾。从这些患者中，在 2018 年接受髋臼周围截骨术治疗的前 12 名患者中，确定了 10 名患者，不包括 2 名临床影像学缺失或质量低下的患者。在 2019 年接受髋臼周围截骨术和同步髋关节镜治疗的前 11 名患者中确定了第二个系列的 10 名患者，不包括一名缺失临床影像学的患者。骨盆和股骨骨表面模型由这两个系列（共 10 例）患者的 CT 扫描生成。有 15 例女性和 5 例男性患者，中位患者年龄为 18 岁 （IQR 17 至 23 岁），术前 LCEA 为 22° （IQR 18° 至 24°），术前 ACEA 为 23° （IQR 18° 至 27°）。 排除标准包括缺少术前 CT 或标准临床影像学成像或严重关节不协调。为了解决我们的第一个研究问题，从分割的 CT 体积中创建了与每位患者的站立 AP 相匹配的数字重建 X 光片和假剖面临床 X 光片。一名获得委员会认证的骨科医生和三名训练有素的研究人员在数字重建的 X 光片上测量了 LCEA 和 ACEA，并将选定的观察点投影回 3D 解剖空间中的坐标中。为了解决我们的第二个研究问题，放射学覆盖角度的观察者内和观察者间一致性与所选骨骼解剖结构的 3D 坐标变化有关。最后，为了解决我们的第三个研究问题，在表盘坐标系中总结了患者髋臼边缘周围被确定为有助于外侧和前侧疼痛点的 3D 位置，并对分离 3D 髋臼贡献的“时间”进行了统计分析。结果导致外侧髋臼缘的 3D 解剖结构是髋臼外侧上缘的可变长度（27 毫米 [IQR 15 至 34 毫米]）跨度，髂下前棘在 35% （20 个中的 7 个） 的臀部中做出贡献。前缘反映了从髂内侧（后内侧到髂前下棘和弓形线前外侧）到髋臼前外侧边缘的 28 毫米（IQR 25 至 31 毫米）的骨跨度。LCEA 的观察者间变异性良好 （类内相关系数 [ICC] 0.82 至 0.83），ACEA 中等至良好 （ICC 0.73 至 0.79），而已识别的 3D 来源位置的一致性差异很大 （ICC 0.32 至 0.95）。 有助于前臼的 3D 解剖结构的髋臼边缘与有助于外侧臼的髋臼缘的圆周范围重叠。结论 将有助于结构性髋关节畸形诊断的二维放射学标志投影到 3D 中，可以识别有助于放射学可见的前侧边缘的重叠骨解剖结构。临床相关性 这项工作利用数字重建的 X 光片和 3D 骨盆解剖结构发现，关节外的骨骼有助于酸骨的放射学外观，并且可能会不同程度地混淆关节覆盖率的估计。此外，有助于测量 LCEA 和 ACEA 的髋臼骨之间的大量重叠表明这些角度测量相似的髋臼畸形，并且需要额外的措施来评估独立于横向覆盖的前部覆盖。