The Effect of Humeral Head Depressor Muscle Co-Activation Training on Functional Outcomes in Patients Undergoing Arthroscopic Shoulder Surgery After Middle-Size Rotator Cuff Muscle Tear

Shoulder pain is one of the most common types of musculoskeletal pain syndroms in the general population as its prevalence has been estimated between 7% and 26% and its annual incidence between 0.9% and 2.5%. Rotator cuff tear is one of the most common causes of painful shoulders. Lack of coordination or weakness of scapulothoracic and scapulohumeral muscles is one of the main factors thought to lead to muscle tears in shoulder. More specifically, the inability of the scapular muscles to achieve superior rotation and posterior tilt, as well as the failure of rotator cuff muscles to counter the superior humeral head translation imposed by deltoid contraction can lead to impingement of the subacromial soft tissues while performing overhead dynamic tasks. This increases the rotator cuff tears' prevalance. Aside from rotator cuff muscles, opposition of superior humeral head translation can be achieved by the glenohumeral adductors (i.e. pectoralis major, latissimus dorsi muscles, and teres major), which act as humeral head depressors by means of the medio-inferior vector created by the orientation of their tendons. Recruitment of the glenohumeral adductors has been shown to decrease subacromial narrowing in elevated arms in asymptomatic individuals, and is thought to be a coping mechanism to decrease pain in individuals with rotator cuff tear. However, to the best of our knowledge, the efficacy of humeral head depressor muscle co-activation training on functional outcomes in patients undergoing arthroscopic shoulder surgery after middle-size rotator cuff muscle tear has never been evaluated in patients with middle-size rotator cuff muscle tear. Since recruitment of those muscles could prevent a decrease in subacromial space during arm elevation, it could potentially lead to improved exercise performance, earlier benefits and better treatment outcomes compared to routine rotator cuff strengthening exercises. Thus, the aim of this study was to investigate the efficacy of the humeral head depressor muscle co-activation training on functional outcomes in patients undergoing arthroscopic shoulder surgery after middle-size rotator cuff muscle tear.