SHOULDER JOINT 305 



ment. The rent in the capsule almost invariably takes place in this situation, between the 

 tendon of the Subscapularis and the Triceps, and through it the head of the bone escapes, so 

 that the dislocation in most instances is primarily subglcnoid. The head of the bone does not 

 usually remain in this situation, but generally assunr es some other position, which varies accord- 

 ing to the direction and amount of force producing the dislocation and the relative strength of 

 the muscles in front and behind the joint. In consequence of the muscles at the back being 

 weaker than those in front, and especially on account of the long head of the Triceps preventing 

 the bone passing backward, dislocation forward is much more common than backward. The 

 most frequent position which the head of the humerus ultimately assumes is on the front of the 

 neck of the scapula, beneath the coracoid process, and hence named subcoracoid dislocation. 

 Occasionally, in consequence, probably, of a greater amount of force being brought to bear on 

 the limb, the head is driven farther inward, and rests on the upper part of the front of the thorax, 

 beneath the clavicle (subclavicular). If the head of the bone passes under the Subscapularis 

 muscle and also under the Teres major or the lower border of the Pectoralis major, the arm 

 remains abducted, or even with the elbow raised above the head (luxatio erecta). Sometimes 

 the humerus remains in the position in which it was primarily displaced, resting on the axillary 

 border of the scapula (subylenoid), and rarely it passes backward and remains in the infra- 

 spinous fossa beneath the spine (subspinous). If dislocation frequently recurs the condition may 

 be amended in some cases by exposing the capsule and putting tucks in it by means of sutures. 



An old unreduced dislocation is sometimes treated by incising the soft parts and returning 

 the head of the humerus into the glenoid cavity. In other cases the head of the humerus is 

 excised. Dislocation of the long tendon of the Biceps muscle from the bicipital groove is a rare 

 accident. When it occurs the arm is rigid in abduction, but the head of the humerus is found 

 to be in the glenoid cavity. It is reduced by flexion of the elbow and rotation of the arm. Rup- 

 ture of the long tendon of the Biceps is more common than dislocation of the tendon. After this 

 injury the belly of the muscle is relaxed and is nearer than normal to the elbow; flexion of 

 the forearm is much weakened, and is weaker in supination than it is in pronation. The head 

 of the humerus passes forward .and inward, and the condition is often mistaken for dislocation 

 of the bone. 



If we desire to aspirate the shoulder-joint, place the arm against the side, flex the forearm at 

 a right angle to the arm, carry the forearm across the front of the thorax, and enter the trocar 

 below the acromion (De Vos). 



The shoulder-joint is sometimes the seat of all those inflammatory affections, both acute and 

 chronic, which attack joints, though perhaps it suffers less frequently than some other joints of 

 equal size and importance. Acute synovitis may result from injury, rheumatism, or pyemia, or 

 may follow secondarily on the so-called acute epiphysitis of infants. It is attended with effusion 

 into the joint, and when this occurs the capsule is evenly distended and the contour of the joint 

 rounded. Special projections may occur at the site of the openings in the capsular ligament. 

 Thus, a swelling may appear just in front of the joint, internal to the lesser tuberosity, from 

 effusion into the bursa beneath the Subscapularis muscle; or, again, a swelling which is some- 

 times bilobed may be seen in the interval between the Deltoid and Pectoralis major muscles, 

 from effusion into the diverticulum, which runs down the bicipital groove with the tendon of the 

 Biceps. The effusion into the synovial membrane can be best ascertained by examination from 

 the axilla, where a soft, elastic, fluctuating swelling can usually be felt. The bursa beneath the 

 Deltoid is sometimes ruptured by violence, and sometimes inflames, suppurates, or becomes 

 tuberculous. 



Tuberculous arthritis not infrequently attacks the shoulder-joint, and may lead to total 

 destruction of the articulation, when ankylosis may result or long-protracted suppuration may 

 necessitate excision. This joint is also one of those which is most liable to be the seat of osteo- 

 arthritis, and may also be affected in gout and rheumatism; or in locomotor ataxia, when it 

 occasionally becomes the seat of Charcot's disease. 



Excision of the shoulder- joint may be required in cases of arthritis (especially the tubercu- 

 lous form) which have gone on to destruction of the articulation; in compound dislocations and 

 fractures, particularly those arising from gunshot injuries, in which there has been extensive 

 injury to the head of the bone; in some cases of old unreduced dislocation, where there is much 

 pain ; and possibly in some few cases of growth connected with the upper end of the bone. The 

 operation is best performed by making an incision from the middle of the coracoacromial liga- 

 ment down the arm for about three inches; this will expose the bicipital groove and the tendon 

 of the Biceps, which may be either divided or hooked out of the way, according as to whether it 

 is implicated in the disease or not. The capsule is then freely opened, and the muscles attached 

 to the greater and lesser tuberosities of the humerus divided. The head of the bone can then 

 be thrust out of the wound and sawed off, or divided with a narrow saw in situ and subsequently 

 removed. The section should be made, if possible, just below the articular surface, so as to 

 leave the bone as long as possible. The glenoid cavity must then be examined, and gouged 

 if carious. 



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