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How to Best Identify Acetabular Retroversion on Radiographs: Thresholds to Guide Clinical Practice
Jeroen C F Verhaegen1,2,3, Camille Vorimore1, Claudia Galletta4
1Division of Orthopaedic Surgery, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada.
The American Journal of Sports Medicine
|August 21, 2024
Summary
Acetabular retroversion can be accurately identified using the crossover sign (COS) and anterior/posterior wall indices (AWI/PWI). Specific thresholds for these radiographic measures, considering AIIS morphology and pelvic tilt, improve diagnostic accuracy for hip impingement.
Area of Science:
- Orthopedics
- Radiology
- Hip Preservation Surgery
Background:
- Acetabular retroversion is linked to hip impingement and instability, necessitating accurate radiographic assessment for treatment planning.
- Radiographic signs like the crossover sign (COS), anterior wall index (AWI), and posterior wall index (PWI) are crucial for evaluating acetabular version and coverage.
- Pelvic tilt (PT) and anterior inferior iliac spine (AIIS) morphology can influence acetabular radiographic appearance, varying between supine and standing positions.
Purpose of the Study:
- To compare acetabular appearance in supine versus standing positions in patients with hip pain.
- To identify factors influencing radiographic measures (COR, AWI, PWI), including acetabular version, AIIS morphology, and spinopelvic characteristics.
- To establish clinical thresholds for radiographic measures to aid in the diagnosis of acetabular retroversion and guide management.
Main Methods:
- A cross-sectional study included 134 patients with hip pain undergoing supine and standing pelvic radiography and CT scans.
- Radiographic parameters including crossover sign (COS), crossover ratio (COR), AWI, PWI, and pelvic tilt (PT) were measured.
- Spearman correlation and receiver operating characteristic (ROC) curve analyses were used to correlate radiographic findings with acetabular version and define diagnostic thresholds.
Main Results:
- The crossover sign (COS) was more prevalent in the supine position (55%) than standing (30%), with a 12% mean difference in crossover ratio (COR).
- Supine COR and AWI/PWI ratio strongly correlated with acetabular version (rho = -0.661 and -0.618, respectively).
- Specific thresholds (COR >30%, AWI/PWI >0.6) demonstrated high sensitivity and specificity for detecting acetabular retroversion, particularly when combined.
Conclusions:
- The crossover sign (COS) is common in hip pain patients, but AIIS morphology and pelvic tilt can cause false positives.
- Established thresholds for COR (>30%) and AWI/PWI ratio (>0.6) enhance diagnostic accuracy for acetabular retroversion.
- Axial cross-sectional imaging may be beneficial in cases with high COR or AWI/PWI ratios to confirm or exclude retroversion.
