Diagnosis of acetabular retroversion: Three signs positive and increased retroversion index have higher specificity and higher diagnostic accuracy compared to isolated positive cross over sign

Abstract

Objectives: The crossover-sign (COS) is a radiographic sign for diagnosis of acetabular-retroversion(AR) in patients with femoroacetabular-impingement (FAI) but overestimates AR. Three signs combined with retroversion-index (RI) could potentially improve diagnostic-accuracy. Aims: (1) To calculate central acetabular-version (AV, CT/MRI) in patients with isolated positive COS and in patients with three radiographic signs for AR on radiographs (AP). (2) To calculate diagnostic performance of positive COS and of three signs combined with retroversion-index (RI) > 30% on radiographs (AP) to detect global AR (AV 30% to detect central AV 30% on radiographs compared to patients with positive COS (18 ± 7°). (2) Sensitivity and specificity of three signs combined with RI > 30% on radiographs was 85% and 63% (87% and 23% for COS). Negative-predictive-value (NPV) was 94% (93% for COS) to rule out global AR (AV < 10°, CT/MRI). Diagnostic accuracy increased significantly (p < 0.001) from 31% (COS) to 68% using three signs. Conclusion: Improved specificity and diagnostic accuracy for diagnosis of global AR can help to avoid misdiagnosis. Global AR can be ruled out with a probability of 94% (NPV) in the absence of three radiographic signs combined with retroversion-index < 30% (e.g. isolated COS positive).

Keywords

• Acetabular retroversion
• Femoroacetabular impingement (FAI)
• Hip preservation surgery
• Acetabular version
• Cross over sign