Objectives: To determine whether positioning of the arm in adduction and internal rotation would improve the confidence in the diagnosis of Bankart lesions in first time shoulder dislocators. Methods: Eleven patients were imaged on an open bore MRI within 1-6 days of traumatic shoulder dislocation with the arm adducted and internally rotated, and subsequently the patients were reimaged with the arm adduced and externally rotated. Two blinded musculoskeletal radiologists determined the confidence of diagnosing labral tears in each of the two positions. Results: An anterior-inferior labral tear was diagnosed in 11/11 patients in internal rotation and in 6/11 patients in external rotation. The average confidence was 2.8 in internal rotation and 1.5 in external rotation (on a scale of 0-3). Using a Wilcoxon signed rank test, the certainty of the diagnosis was determined to be significantly higher with the arm in internal rotation (P = 0.016). Conclusions: MRI performed with the arm in internal rotation for patients with acute first time anterior shoulder dislocation increases the certainty of the diagnosis of anterior-inferior labral tears. Key Points: • Adduction and internal arm rotation improves the MRI diagnosis of Bankart tears. • Arm positioning in ADIR has distinct advantages over abduction and external rotation. • Early imaging after shoulder dislocation may provide a diagnostically useful "arthrographic" effect.
- Anterior shoulder dislocation
- Bankart lesion
- Glenohumoral labral tear
- Magnetic resonance imaging (MRI)
- Shoulder instability