Sonography of full-thickness supraspinatus tears: comparison of patient positioning technique with surgical correlation.

OBJECTIVE: Sonography has become a popular technique for the assessment of musculoskeletal disorders. Patient positioning is crucial to a thorough and accurate assessment of rotator cuff tendons. Two positions, the Crass and modified Crass, have been routinely used in the research and clinical settings to examine the supraspinatus tendon. Our study was a prospective trial to determine whether the Crass or the modified Crass position affords the most accurate measure of supraspinatus tears when compared with surgical findings. SUBJECTS AND METHODS: Twenty-one patients with full-thickness supraspinatus tears underwent shoulder sonography in both the Crass and the modified Crass positions. Measurements of supraspinatus tears were performed in the sagittal and transverse dimensions. Patients subsequently underwent either arthroscopic or open supraspinatus repair. Intraoperative measurements were made in two dimensions and were compared with sonographic findings. RESULTS: Sonography had 100% specificity in detecting full-thickness supraspinatus tears. No statistically significant difference was seen between the size of supraspinatus tears in the Crass and modified Crass positions and surgical findings in the transverse plane (p = 0.55 and 0.61, respectively). In the sagittal dimension, no statistically significant difference was seen between surgical findings and the Crass position (p = 0.14); however, a difference existed when the modified Crass position was used (p = 0.03). CONCLUSION: Sonography reliably detects and quantifies supraspinatus tears. Both the Crass and the modified Crass positions reflected the true size of supraspinatus tears in the transverse plane. In the sagittal plane, the Crass position is the more useful to quantify supraspinatus tears because the modified Crass position overestimates the size of such tears.