Muscle Activity Before and After Subacromial Injection.
CONTEXT
Shoulder muscle activation in patients with subacromial impingement is highly cited and variable in the literature. Differences between studies could be due to artifacts introduced by normalization practices in the presence of pain. Ultimately, this lack of knowledge pertaining to pathogenesis limits the clinical treatment and restoration of muscular function.


DESIGN
A total of 21 patients with stage 2 subacromial impingement and 21 matched controls were recruited for EMG testing of their affected shoulder during an arm elevation task. The patients were tested before and after receiving an injection to their subacromial bursa.


METHODS
The EMG from 7 shoulder muscles were measured before and after treatment during humeral motion in the scapular plane.


RESULTS
Our findings indicate an increase in anterior deltoid, middle deltoid, and upper trapezius activity following the injection; further, this trend extended to the controls. The control subjects had a greater activation of the latissimus dorsi at peak arm elevation when compared with the patient group postinjection.


CONCLUSIONS
Our results indicate that a reduction in subacromial pain is associated with changes in shoulder muscle recruitment, primarily of the deltoid. This change in deltoid activity may lend evidence to rotator cuff function in patients without rotator cuff tears.
['Ettinger|Lucas|L|', 'Shaprio|Matthew|M|', 'Karduna|Andrew|A|']
D004576:Electromyography D006801:Humans D016059:Range of Motion, Articular D017006:Rotator Cuff D019534:Shoulder Impingement Syndrome D064171:Superficial Back Muscles
subacromial impingement EMG shoulder muscle recruitment anesthetic injection