Objective: Assessment of rotator cuff muscle atrophy is an important component of the shoulder sonogram. We hypothesized that extended-field-of-view (EFOV) sonography would allow greater interrater reliability than conventional sonography for the evaluation of rotator cuff muscle atrophy.
Materials and methods: This retrospective study involved 50 consecutive patients who presented for shoulder sonography. All patients underwent EFOV imaging of the supraspinatus and infraspinatus muscles in addition to conventional imaging of each muscle. Five musculoskeletal radiologists first assessed 50 EFOV images of the supraspinatus and infraspinatus muscles and scored both muscles using a scale of 1-5. The reliability of each method was determined by calculating intraclass correlation coefficients (ICCs) according to a method developed by Shrout and Fleiss. The significance of the difference between reliabilities for conventional images and EFOV images was tested with a z-test.
Results: For the EFOV images, the ICC for the supraspinatus muscle was 0.77 and for the infraspinatus, 0.75. For the conventional images, the ICC for the supraspinatus muscle was 0.52 and for the infraspinatus, 0.57. The degree of interrater reliability for the five readers in our study was significantly higher for the EFOV images than for the conventional images (p < 0.0001).
Conclusion: EFOV sonography results in greater interrater reliability than conventional sonography for the detection of rotator cuff muscle atrophy. EFOV images of the rotator cuff muscles should be obtained as part of routine shoulder sonography.