A comprehensive analysis of the swimmers' shoulder
Creators: name: McKim, Kevin Robert
Publisher: name: University of British Columbia
Year: 2009

description: Shoulder impingement syndrome is the most frequent injury suffered by the competitive swimmer. The literature is very thorough in describing the signs and symptoms of this condition. However, there is still a great deal of controversy in the published data about the etiology of shoulder impingement syndrome. Much of the debate undoubtedly exists because the cause of rotator cuff injury in one specific population may be different than in another population. For example elderly patients probably develop rotator cuff injury for different reasons than young athletes. The purpose of this study is to examine the role of seven common etiologic factors in the development of shoulder impingement syndrome. One hundred and seven competitive swimmers were recruited into the study. Each subject was classified as either acutely injured age-group (n=20), history of injury agegroup (n=35), non-injured age-group (n=40) or chronically injured master (n=12). The subjects were tested for differences in shoulder flexibility, glenohumeral joint laxity, posterior capsule inflexibility, rotator cuff strength and balance, rotator cuff endurance, scapulothoracic muscle strength, workload, swimming stroke technique, and acromial morphology. Workload and technique were evaluated with questionnaires. Shoulder flexibility and posterior capsule inflexibility were measured with a goniometer to determine range of motion. Joint laxity was tested by using anterior, posterior and inferior drawer tests. Rotator cuff strength and endurance were measured on a Cybex II Isokinetic Dynamometer. Finally, acromial morphology was examined in the injured subjects with a Supraspinatus Outlet View Radiograph. The results seem to indicate that the shape of the acromion does not influence shoulder injury in a young athletic population. No significant differences were noted in the technique analysis among the age group swimmers. The test procedure was too insensitive to detect differences in the scapulothoracic muscles. The injured athletes had significantly reduced posterior capsule flexibility. They were also found to have a significant degree of anterior and inferior glenohumeral translation. No differences were noted in the strength or muscle balance of the internal and external rotators of the shoulder. It appears that all competitive swimmers have strength imbalances between the strong internal rotators and the relatively weak external rotators. The injured subjects also had a trend towards reduced external rotation endurance. The mechanism of injury in the young competitive swimmer appears to be a combination of acquired joint laxity, rotator cuff imbalances and posterior capsule inflexibility. These mechanisms result in the anterior and superior migration of the humeral head. Humeral head migration causes compression and mechanical abrasion of the supraspinatus tendon between the head of the humerus and coracoacromial arch eventually leading to tendon inflammation, degeneration, and rupture. This study does not provide a definitive explanation for every case of shoulder impingement syndrome. It does provide relevant information about the condition of the competitive swimmer's shoulder and gives a possible explanation about the etiology of shoulder impingement syndrome.