The relevance of the radiological signs of acetabular retroversion among patients with femoroacetabular impingement

Abstract

Orthopaedic surgeons have accepted various radiological signs to be representative of acetabular retroversion, which is the main characteristic of focal over-coverage in patients with femoroacetabular impingement (FAI). Using a validated method for radiological analysis, we assessed the relevance of these signs to predict intra-articular lesions in 93 patients undergoing surgery for FAI. A logistic regression model to predict chondral damage showed that an acetabular retroversion index (ARI) > 20%, a derivative of the well-known cross-over sign, was an independent predictor (p = 0.036). However, ARI was less significant than the Tönnis classification (p = 0.019) and age (p = 0.031) in the same model. ARI was unable to discriminate between grades of chondral lesions, while the type of cam lesion (p = 0.004) and age (p = 0.047) were able to. Other widely recognised signs of acetabular retroversion, such as the ischial spine sign, the posterior wall sign or the cross-over sign were irrelevant according to our analysis. Regardless of its secondary predictive role, an ARI > 20% appears to be the most clinically relevant radiological sign of acetabular retroversion in symptomatic patients with FAI.

Radiographic Diagnosis of Pincer-Type Femoroacetabular Impingement: A Systematic Review

“…Both the radiographic markers showed poor sensitivity and specificity and were limited by pelvic tilt and inherent inaccuracy associated with plain radiographs. 50 The only study that used intraoperative findings as a gold standard to assess the accuracy of those radiographic markers was a retrospective study conducted by Diaz-Ledezma et al, 14 and their study found that these markers do not correlate with intraoperatively found chondral damage. 14 Although some studies show the accuracy of findings obtained from plain radiographs, 10,11,33,45,46 diagnosing patients solely on radiographic findings may yield inaccuracies.…”

“…A study by Wassilew et al 50 also showed that crossover sign and posterior wall sign are not accurate markers to assess for acetabular version when compared with CT findings. In addition, a study by Diaz-Ledezma et al 14 concluded that crossover sign, posterior wall sign, and ischial spine sign do not correlate with chondral damages that are identified intraoperatively, which reliably predicts symptomatic pincer-type FAI. Herniation pit is an occasionally utilized radiographic marker to diagnose FAI, but its correlation with pincer-type impingement is unclear.…”

Are “normal hips” being labeled as femoroacetabular impingement due to EE angle?

“…In this study, the EE angle was selected to quantify the abnormal bone structure of the hip joint in FAI. The EE angle reflects the degree of the acetabular retroversion in the Pincer-type FAI, which is one of the features of Pincer-type FAI, [16,17] typically manifesting as decreased EE angle. The study of a large sample by Werner et al [5] showed that the EE angle of the acetabular edge “crossing” negative group was 21.0°, while that of the “crossing” positive group was 17.3 °.…”

The current situation in hip arthroscopy

“…Although focal anterior overcoverage, acetabular retroversion, abnormal acetabular index, coxa profunda, acetabular protrusio, ischial spine sign, cross-over sign and posterior wall sign are widely described in different studies, their variability casts doubt on their routine use to guide surgical treatment. 8,35-37 Correction of a ‘pincer’ type deformity should be performed with acetabular rim trimming. Excessive acetabular rim trimming should be avoided, since 1 mm rim trimming will decrease by approximately 2.4° of the CE angle.…”