Indirect MR Arthrography of the Shoulder:Use of Abduction and ExternalRotationtoDetectFull-and Partial-ThicknessTearsofthe SupraspinatusTendon1

Purpose: To evaluate prospectively the accuracy of indirect magnetic resonance (MR) arthrography for supraspinatus tendon tears during neutral positioning or abduction and external rotation (ABER) and neutral positioning. Materials and Methods: Informed consent was obtained in all patients, and the study was approved by the institutional review board. Indirect MR arthrography of the shoulder was performed in 51 symptomatic patients ( 14 female, 37 male; mean age, 47 years) in the neutral position ( set 1) and in the neutral and ABER positions ( set 2). Two readers independently interpreted both sets, and diagnoses were compared with arthroscopic findings. Diagnostic accuracy was calculated, and 95% confidence intervals were used to detect significant differences between sets. Diagnostic confidence was recorded by using a three-level confidence score. Differences between sets were evaluated by using the Wilcoxon signed rank test. Interobserver agreement was determined separately for each set and for all diagnoses, full-thickness tears, and partial-thickness tears. Results: For full-thickness tears, there was no benefit to reading set 2. For reader 1, sensitivity and specificity were 95% and 100%, respectively, for set 1 and 100% and 100%, respectively, for set 2. For reader 2, sensitivity and specificity were 80% and 100%, respectively, for set 1 and 100% and 100%, respectively, for set 2. For partial-thickness tears, sensitivity was significantly higher after reading set 2. For reader 1, sensitivity and specificity were 71% and 88%, respectively, for set 1 and 93% and 100%, respectively, for set 2. For reader 2, sensitivity and specificity were 50% and 88%, respectively, for set 1 and 86% and 94%, respectively, for set 2. For both readers, diagnostic confidence for partial-thickness tears was significantly higher after reading set 2. After the interpretation of set 2, k values increased from 0.35 to 1.00 for full-thickness tears and from 0.12 to 0.63 for partial-thickness tears. Conclusion: Indirect MR arthrography with supplementary images obtained with patients in the ABER position significantly improved sensitivity and increased diagnostic confidence for partial-thickness tears of the supraspinatus tendon. Interobserver agreement was improved for both full- and partial-thickness tears.