The Activities of Trapezius and Deltoid in Rotator Cuff Tear Patients Injected Local Anesthetics in Subacromial Space

ABSTRACT

OBJECTIVE: To investigate the activities of upper trapezius and deltoid muscles in shoulder abduction in full can and empty can position in rotator cuff tear patients. METHOD: Twelve subjects with right rotator cuff tear patients participated in this study. Each subject performed scapular plane abduction with humeral external rotation (full can position) and with humeral internal rotation (empty can position). Electromyography (EMG) was recorded with surface electrodes at the both upper trapezius, anterior, lateral, and posterior deltoid muscles during shoulder abduction. The EMG activity of each muscle was normalized according to the highest EMG activity during a maximum manual muscle test for the corresponding muscle. RESULTS: Muscle activities of the lesion side's upper trapezius and lateral deltoid were significantly greater than those of the normal side in full can position. In empty can position, the activities of upper trapezius, anterior, and lateral deltoid increased in lesion side. In comparison between full can and empty can exercises, over 30degrees abduction arcs, empty can exercise showed increased muscle activities of upper trapezius and all deltoid muscle in lesion side. In contrast, anterior and lateral deltoid only showed increased in the muscle activities under empty can exercise in sound side. CONCLUSION: Rotator cuff tear is involved in changed the activities of upper trapezius and deltoid muscles. And these results suggested that in rotator cuff tear patients, the changed pattern of muscle contraction should be considered in shoulder exercise.