r 



Acromion 



Head of. 

 humerus 



Deltoid 



Pectoral is 

 major 



PRACTICAL CONSIDERATIONS : AXILLA AND SHOULDER. 583 



and the supracoracoid , in which, owing to fracture of the coracoid or the acromion, 

 the head is displaced upward, are so uncommon that they need merely be mentioned 

 here. The backward (subspinous) luxation is resisted so strongly by the subscapu- 

 laris, and especially by the long head of the triceps, that it also is a surgical rarity. 



In the subglenoid and subcoracoid varieties (Figs. 565, 566) it will be found : 

 I. That the normal curve of the shoulder is replaced by a straight line, because of 

 (a) the absence of the head of the bone and the tuberosities beneath the deltoid ; 

 (d) the stretching of that muscle. 2. For the same reasons it will be found that 

 (a) a ruler applied to the outer Side of the arm will touch both the acromion and the 

 external condyle at the same time (Hamilton) ; and (d) the edge of the acromion is 

 unnaturally prominent, while beneath it is a palpable depression instead of the nor- 

 mal resistance of the tuberosities. 3. The elbow is abducted because of the tension 

 of the deltoid. 4. The forearm is flexed on account of the tension of the biceps, 

 5. The vertical measurement of the axilla 



is increased (Callaway), because of {a) Fig. 567. 



the presence of the head or upper por- '"^T^: , 



tion of the shaft in the line of meas- 

 urement ; and (d) the lowering of the 

 axillary folds (Bryant), the insertions 

 of the pectoralis major and latissimus 

 dorsi being, of course, carried down- 

 ward with the humerus. 6. The elbow 

 cannot be made to touch the chest-wall 

 while the hand is placed on the oppo- 

 site shoulder (Dugas), because the head 

 of the bone is held in contact with that 

 wall by the tense muscles and overlying 

 structures, and its lower extremity — 

 the other end of a straight, inflexible 

 axis — cannot be made at the same time 

 to touch at a second point the curve 

 represented by the wall of the thorax. 

 7. There is rigidity because of the ten- 

 sion or spasm of the muscles moving 

 the humerus, especially of the sub- 

 scapularis, the deltoid, the supra- and 

 infraspinatus, the biceps, and the coraco- 

 brachialis. 8. In the subcoracoid luxa- 

 tion the prominence of the head may be 

 felt beneath the coracoid or outer third 

 of the clavicle where it lies, the anatom- 

 ical neck resting on the anterior border 

 of the glenoid cavity. There is a little 

 real lengthening, — i.e., the distance between the glenoid surface and the lower end 

 of the humerus must be increased, — but this may be converted into apparent short- 

 ening by abduction, which approximates the tip of the acromion and the external 

 condyle. 9. In the subglenoid variety the head may be felt low in the axilla, the 

 anterior wall of which is widened. It rests on the upper part of the outer border of 

 the scapula just below the glenoid cavity. Lengthening is apt to be marked, and, 

 when the arm is adducted somewhat, may exceed an inch. The stretching and 

 ' ' hollow tension' ' of the deltoid and, therefore, the abduction of the arm are 

 marked. 10. There is usually (a) pain from direct pressure upon or from stretch- 

 ing of the brachial plexus, and frequently (d) oedema from similar involvement of 

 the axillary vessels. 



In all luxations, but especially in the subglenoid and subspinous, the circumflex 

 nerve is apt to be injured ; hence obstinate paresis or paralysis of the deltoid is a 

 not infrequent sequel. 



In all methods of reduction of shoulder luxacions the humerus is used as a 

 lever, and in all it is desirable to secure fixation of the scapula by means of (a) the 



Triceps 



Biceps 



\ 



Superficial dissection of preceding subcoracoid luxation, 

 showing muscles after removal of skin and fascias. 



