Anterior-inferior labral lesions of recurrent shoulder dislocation evaluated by MR arthrography in an adduction internal rotation (ADIR) position

Purpose: To introduce and evaluate the usefulness of the adduction internal rotation (ADIR) position in MR arthrography for discriminating the following subtypes of Bankart lesions: classic Bankart lesions, anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesions, and Perthes lesions. Materials and Methods: The study group consisted of 25 patients who had been referred for MR arthrography of the shoulder and then underwent arthroscopy due to recurrent episodes of shoulder dislocation. MR arthrography was performed in three different positions: neutral, abduction external rotation (ABER), and ADIR. The authors evaluated the statistical significance of the method's discriminative diagnostic ability for the subtypes of Bankart lesions according to the position changes. Results: Twenty-three patients had the following single or complex labral lesions: classic Bankart (N = 8), ALPSA (N = 3), complex classic Bankart/ALPSA (N = 8), and complex ALPSA/Perthes (N = 4). Two patients had no visible antero-inferior labral lesions. The performance of ADIR positioning for differentiating ALPSA lesions was superior to the neutral or ABER positioning. The difference of the discriminative lesion detection ability was statistically significant (P <.01) only for detecting ALPSA lesions in the ADIR position. Conclusion: MR arthrography in the ADIR position provides high accuracy for the diagnosis of ALPSA lesions, and complements routine MR arthrography when used to diagnose labroligamentous lesions in patients with recurrent shoulder dislocations.