Background:Acetabular retroversion is associated with impingement and instability. An adequate interpretation of acetabular version and coverage on radiographs is essential to determine the optimal treatment strategy (periacetabular osteotomy vs hip arthroscopic surgery). The crossover sign (COS) has been associated with the presence of acetabular retroversion, and the anterior wall index (AWI) and posterior wall index (PWI) assess anteroposterior acetabular coverage. However, the radiographic appearance of the acetabulum is sensitive to anterior inferior iliac spine (AIIS) morphology and pelvic tilt (PT), which differs between the supine and standing positions.Purpose:To (1) identify differences in the acetabular appearance between the supine and standing positions among patients presenting with hip pain; (2) determine factors (acetabular version, AIIS morphology, and spinopelvic characteristics) associated with the crossover ratio (COR), AWI, and PWI; and (3) define relevant clinical thresholds to guide management.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Patients who presented to a hip preservation surgical unit (n = 134) were included (mean age, 35 ± 8 years; 58% female; mean body mass index, 27 ± 6). All participants underwent supine and standing anteroposterior pelvic radiography to assess the COS, COR, AWI, and PWI as well as standing lateral radiography to determine standing PT. Computed tomography was used to measure supine PT, acetabular version, and AIIS morphology. Acetabular version was measured at 3 transverse levels, corresponding to the 1-, 2-, and 3-o’clock positions. The correlation between radiographic characteristics (COR, AWI, and PWI) and acetabular version, AIIS morphology, and PT was calculated using the Spearman correlation coefficient. Receiver operating characteristic curve analysis was performed to define thresholds for the COR, AWI, and PWI to identify retroversion (version thresholds: <10°, <5°, and <0°).Results:The COS was present in 55% of hips when supine and 30% when standing, with a mean difference in the COR of 12%. The supine COR (rho = −0.661) and AWI/PWI ratio (rho = −0.618) strongly correlated with acetabular version. The COS was more prevalent among patients with type 2 AIIS morphology (71%) than among those with type 1 AIIS morphology (43%) ( P = .003). COR thresholds of 23% and 28% were able to identify acetabular version <5° (sensitivity = 81%; specificity = 80%) and <0° (sensitivity = 88%; specificity = 85%), respectively. An AWI/PWI ratio >0.6 was able to reliably identify acetabular version <0° (sensitivity = 83%; specificity = 84%). In the presence of a COR >30% and an AWI/PWI ratio >0.6, the specificity to detect retroversion was significantly increased (>90%).Conclusions:The presence of the COS was very common among patients with hip pain. False-positive results (high COR/normal version) may occur because of AIIS morphology/low PT. Relevant thresholds of COR >30% and AWI/PWI ratio >0.6 can help with diagnostic accuracy. In cases in which either the COR or AWI/PWI ratio is high, axial cross-sectional imaging can further help to avoid false-positive results.

中文翻译：

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如何在射线照片上最好地识别髋臼后倾：指导临床实践的阈值


背景：髋臼后倾与撞击和不稳定有关。对髋臼版本和放射线照片覆盖范围的充分解释对于确定最佳治疗策略（髋臼周围截骨术与髋关节镜手术）至关重要。交叉征（COS）与髋臼后倾的存在相关，前壁指数（AWI）和后壁指数（PWI）评估前后髋臼覆盖情况。然而，髋臼的放射学外观对髂前下棘 (AIIS) 形态和骨盆倾斜 (PT) 很敏感，仰卧位和站立位之间的髋臼外观有所不同。 目的：(1) 确定仰卧位和站立位之间髋臼外观的差异以及髋部疼痛患者的站立姿势； (2) 确定与交叉比 (COR)、AWI 和 PWI 相关的因素（髋臼版本、AIIS 形态和脊柱骨盆特征）； (3)确定相关的临床阈值以指导管理。研究设计：横断面研究；证据级别，3。方法：纳入髋关节保留手术室就诊的患者 (n = 134)（平均年龄，35 ± 8 岁；58% 女性；平均体重指数，27 ± 6）。所有参与者均接受仰卧位和站立位骨盆前后位 X 线摄影以评估 COS、COR、AWI 和 PWI，以及站立侧位 X 线摄影以确定站立 PT。计算机断层扫描用于测量仰卧位 PT、髋臼版本和 AIIS 形态。在 3 个横向水平处测量髋臼版本，分别对应 1 点、2 点和 3 点钟位置。 使用 Spearman 相关系数计算放射学特征（COR、AWI 和 PWI）与髋臼版本、AIIS 形态和 PT 之间的相关性。进行受试者操作特征曲线分析，以确定 COR、AWI 和 PWI 的阈值，以识别后倾（版本阈值：<10 id=6>0.6 能够可靠地识别髋臼版本<0 id=7>30%，AWI /PWI 比率 >0.6，检测逆转的特异性显着增加 (>90%)。结论：髋部疼痛患者中 COS 的存在很常见，因为可能会出现假阳性结果（高 COR/正常版本）。 AIIS 形态/低 PT 的相关阈值 COR >30% 和 AWI/PWI 比率 >0.6 有助于提高诊断准确性。在 COR 或 AWI/PWI 比率较高的情况下，轴向横截面成像可以进一步提供帮助。以避免假阳性结果。