COMPARISON OF MUSCLES ACTIVITY BETWEEN EMPTY CAN EXERCISE AND FULL CAN EXERCISE USING 18F-FDG PET/CT

Introduction Many literatures regarding more specific tests to diagnose the supraspinatus tendon injuries and the best rehabilitation methods to strengthen the supraspinatus have been published. However, conflicting results have been reported. 2-deoxy-2-[18F] fluoro-D-glucose (FDG) positron emission tomography (PET) has been recently used to assess skeletal muscle activities in various fields. Purpose To evaluate & compare the metabolic activities of deltoid & rotator cuff muscles after the full-can & empty-can exercises using PET-CT. Materials and Methods Ten healthy volunteers (age 27–34/mean 29.8 ± 2.7) with no history of shoulder pain and diabetes mellitus participated in this study. After FDG injection, both arms were maintained in the position of empty can and full can for ten minutes respectively. PET-CT was performed at forty minutes after the injection. The maximum standardized uptake value (SUV) was measured in the anterior, middle and posterior deltoid, supraspinatus, subacapularis and infraspinauts on the entire axial images. Results The middle deltoid and subscapularis showed significantly greater activity during the empty-can exercise than during the full-can exercise (P=.006 and P=.003 respectively). The muscular activity of the supraspinatus also increased during the empty-can exercise than during the full-can exercise, although no statistical difference existed between two exercises. Six cases of eight cases who had increased activity of the subscapularis had increased activity in superior one half of the subscapularis than in lower one half of it, although there is no significant difference between two portions. Conclusion The Empty-can exercise requires more strength of the middle deltoid, subscapularis and supraspinatus to keep the arm in internal rotation. The increased activity of the middle deltoid and subscapularis muscles after the empty-can exercise can make the empty-can test less specific to the supraspinatus muscle. The empty-can test can induce pain and weakness due to the subscapularis pathology. The full-can test can be used to test the function of the supraspinatus with the least amount of surrounding middle deltoid and subacapularis muslce activity.