Electromyographic activity in the immobilized shoulder musculature during ipsilateral elbow, wrist, and finger movements while wearing a shoulder orthosis

Abstract

Shoulder immobilization after rotator cuff surgery is usually prescribed to protect the repaired tendons; however, shoulder orthoses often also immobilize the elbow and wrist joints. There is insufficient evidence to support that elbow and wrist movements can affect repair integrity by highly activating the rotator cuff muscles. The aim of this study was to quantify the electromyographic activity of immobilized shoulder muscles during elbow, wrist, and finger movements. Fifteen shoulder muscles of the dominant limb of 14 healthy subjects were evaluated by use of electromyography with 11 surface electrodes and 4 fine-wire electrodes in the rotator cuff muscles. While wearing a custom orthosis, the subjects completed tests involving elbow, wrist, and finger movements of the ipsilateral limb. The peak activity of each muscle was normalized to maximum voluntary contraction (percent MVC) and averaged across the subjects. Rotator cuff muscles were activated to less than 10% MVC in both slow and fast elbow flexions. The mean peak activations of all muscles during wrist and finger movements were less than 5% MVC. In daily activities such as writing, typing, clicking a computer mouse, and holding a box or bag, rotator cuff muscle activity did not exceed 11% MVC, but sudden movements such as grasping a bottle could show higher levels of activity, which in some individuals exceeded 20% MVC. Elbow, wrist, and finger movements could minimally activate the rotator cuff muscles when the shoulder is immobilized with an orthosis.