The added value of ABER position for the detection and classification of anteroinferior labroligamentous lesions in MR arthrography of the shoulder.

Purpose: The purpose of this study is to compare MR arthrography in abduction and external rotation (ABER) position with conventional MR arthrography in neutral position for the detection and further classification of anteroinferior labroligamentous lesions.
Materials and Methods: Two hundred and twenty-nine cases of shoulder MR arthrography with subsequent arthroscopy were retrospectively evaluated. All MR arthrograms in ABER position and neutral position were independently assessed by two radiologists who were blinded to the arthroscopic findings. Sensitivities and specificities of both positions for detection and further categorization of anteroinferior labroligamentous lesions were calculated and compared using paired McNemar test. K values were calculated to quantify the level of interobserver agreement.
Results: At arthroscopy, 24 Bankart lesions, 59 ALPSA lesions, 39 Perthes lesions, 8 GLAD lesions, 4 ALIPSA lesions, 31 nonclassifiable lesions and 60 intact anteroinferior complexes were found. The sensitivity of MR arthrography in ABER position for detecting anteroinferior labroligamentous lesions was significantly higher than that of in neutral position (92.7-94.5% versus 81.8-83%, P<0.05). For the detection rate of the mentioned 6 subtypes of lesions, only the Perthes lesions had significant improvement in ABER position when compared with conventional MR arthrography (observer 1, 61.5-87.2%, P=0.006; observer 2, 69.2-92.3%, P=0.004). MR arthrography in ABER position was more effective in identifying of Perthes lesions (66.7-74.4% versus 35.9-40%, P<0.05) while the conventional MR arthrography was more effective in accurate diagnose of ALPSA lesions (74.6-78.0% versus 54.2-55.9%, P<0.05). No statistically significant difference of the diagnostic accuracy was found between the two positions for Bankart lesions, GLAD lesions, and ALIPSA lesions.
Conclusion: MR arthrography in ABER position has more added value on detection of Perthes lesions in evaluation of anteroinferior labroligamentous complex tear.
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