THE SHOULDER-GIRDLE. 



255 



Subacromial Bursa. Separating the greater tuberosity from the deltoid 

 muscle, the acromion process, and coraco-acromial ligament, is the large subacromial 

 bursa. It does not communicate with the joint, except rarely in old people. Effu- 

 sions into it cause an increased prominence of the deltoid muscle, and pus seeking 

 an outlet is likely to show itself at the anterior edge of the muscle and less often at 

 its posterior edge. These effusions, which are liable to be present from contusions, 

 sprains, etc. , s*hould not be mistaken for intra-articular accumulations. 



Biceps Tendon. The long tendon of the biceps muscle enters the joint 

 through the bicipital groove between the two tuberosities. With the arm hanging 

 by the side it points directly forward; it passes over the head of the humerus and 

 under the coraco-acromial ligament about midway between the coracoid and acro- 

 mion processes to insert into the upper edge of the glenoid cavity. It is covered 

 by a synovial sheath which passes with it through the opening in the capsule and a 

 short distance along the bicipital groove. As this sheath does not communicate with 

 the joint the tendon is in one sense extra-articular. It is held in the groove by a 



In: 



lection following the 

 ig tendon of the biceps 



FIG. 268. Shoulder- joint distended with injection, showing the position assumed by the humerus. 



fibrous expansion, extending from the pectoralis major tendon below to the capsule 

 above, called the transverse humeral ligament. This ligament is so strong that luxa- 

 tion of the tendon is uncommon; even when the humerus is luxated the tendon is 

 rarely displaced. 



Subscapular Bursa. Beneath the tendon of the subscapularis there is a bursa 

 which frequently communicates with the joint. This opening tends to weaken the 

 capsule and it is at this point and just below that the head bursts through in disloca- 

 tions. 



Infraspinatus Bursa. The capsule of the joint and the synovial membrane 

 may be prolonged beyond the rim of the glenoid cavity under the tendon of the 

 infraspinatus, or a bursa at this point may communicate with the joint. 



Other bursae may be present, but are unimportant. One is between the 

 coracoid process and the capsule and another under the combined tendon of the 

 coracobrachialis muscle and the short head of the biceps. 



Effusions in the Shoulder-joint. Liquid accumulations occur both from 

 injury and disease. The liability of confounding them with those in the subacromial 

 bursa has been alluded to above. As a result of disease, most often osteo-arthritis or 

 tuberculosis, considerable liquid may accumulate in the joint. As the tension in- 

 creases the arm becomes abducted about 50 degrees and the effusion tends to escape 

 through the openings in the capsule (Fig. 268). 



