Electromyographic analysis of rehabilitation for rotator cuff repair

Abstract

Background: The rotator cuff tear is one of common musculoskeletal diseases in old age and the rotator cuff repair is considered as proper treatment for patients showing no improvement with nonsurgical treatment. Although there was debate about the time to start the range of motion exercise, it is important to prevent shoulder stiffness for patients got rotator cuff repair. Self-assisted shoulder and elbow exercises are common home-based rehabilitation, but have been also considered dangerous to the repaired tendon. We assessed differences in the activities of the rotator cuff and parascapular muscles during self-assisted forward flexion (FF) and external rotation (ER) of the shoulder and elbow flexion extension exercises (EFE) with electromyography (EMG). Methods: In total, 15 healthy subjects participated in this prospective study. A self-assisted FF exercise was performed, using a table (FFT), a pulley and rope (FFP), and a cane (FFC), while the self-assisted ER exercise was performed with a cane (ERC) and a wall (ERW). Activation amplitudes of the upper subscapularis, supraspinatus, and infraspinatus were evaluated using fine wires. Bipolar surface electrodes were used to record EMG activities from eight parascapular muscles: anterior, middle, and posterior deltoid, upper trapezius, pectoralis major, latissimus dorsi, serratus anterior, and biceps brachii. The EFE exercise and its modification by holding the upper arm with the contralateral hand (EFEH) were also performed. The peak and mean values of muscle activity were normalized to the maximal voluntary isometric contraction (MVIC).Results: In the FFC exercise, peak activities of cuff muscles were above 10% (11-24%), while when using a rope and pulley, only the activity of the supraspinatus was above 10% (17%). The FFT showed peak EMG activities below 10% of MVIC in all rotator cuff muscles (1 10%). Regarding the tools used, the supraspinatus and infraspinatus showed lower peak EMG activities when using a table compared with a cane (P < 0.01 in both the supraspinatus and infraspinatus) and a pulley and rope (P < 0.05 in both the supraspinatus and infraspinatus). Forward flexion of < 90° decreased peak supraspinatus activation versus 170° (P = 0.047). In the ER exercise using the cane and wall, activities of the upper subscapularis were both over 10% (15 27%). However, there was no difference between the tools, used such as the cane and wall, in peak EMG activities in the rotator cuff (P > 0.05 in the supraspinatus, infraspinatus, and upper subscapularis). The EFE exercise showed activities above 10% in the upper subscapularis and supraspinatus (13-18%), The EFEH exercise resulted in lower peak EMG activity in the supraspinatus than the EFE (P = 0.018). Mean EMG activities in the rotator cuff muscles showed differences between the tools used during the FF, ER, and EFE with similar peak EMG activities. No parascapular muscles showed a peak % MVIC of more than 10% in the FF exercises, except the anterior and middle deltoid and the serratus anterior, which showed 16.1%, 13.3%, and 16.5%, respectively, during the FFC.Conclusions: The table sliding exercise may cause less stress in the rotator cuff tendon in self-assisted forward flexion compared with the cane or the pulley and rope. Decreasing the range of motion below 90° in forward flexion activated the supraspinatus less. Two methods, the wall and cane, resulted in different activation of parascapular muscles during the external rotation movement of the shoulder. Moreover, movement of the elbow can be performed with the contralateral hand holding the upper arm to activate the rotator cuff and upper trapezius to a lesser extent.