584 



HUMAN ANATOMY. 



Clavicle 



Coracoid 

 process 



Long head 

 of biceps 



Supraspinatus 



Infraspinatus 



Teres minor 



Deltoid 



weight of the trunk in the supine and recumbent position ; (d) pressure on the 

 acromion and clavicle ; (r) the use of a folded sheet placed high in the axilla, so 

 that it presses upon the axillary border in front and the dorsum posteriorly when 

 th 2 two ends are carried across the body and made taut ; or {d ) by dragging on 

 tne opposite arm, "which, by making tense the trapezius of the opposite side, pro- 

 vokes contraction of the muscle on the injured side" (Makins). 



The use of the heel or foot in the axilla as a fulcrum while manual extension is 

 made — the long arm of the lever, the shaft of the humerus, being carried inward so 

 as to move the short arm, the head, outward — requires no anatomical explanation. 



Kocher's method (applicable especially to subcoracoid luxation) is more com- 

 plex in its mode of action. There is some difference of opinion as to its exact 

 mechanism, but it is safe to say that in its various stages it acts approximately as 

 follows. I. The elbow is fle.xed, rela.xing the biceps, and the arm is pressed closely 

 to the side, making tense the untorn posterior portion of the capsule extending 

 between the posterior lip of the glenoid fossa and the under and back part of the 



neck of the humerus. This 

 Fig 568. portion of the capsule and the 



tendons of the posterior scapu- 

 lar muscles are drawn tightly 

 across the glenoid fossa. 2. 

 The arm is rotated outward 

 vintil the forearm is parallel 

 with the transverse axis of the 

 body, the hand pointing di- 

 rectly outward. This rolls the 

 head of the bone outward on 

 the tense portion of the cap- 

 sule, which is partly wound, 

 as it were, upon the neck, and 

 at the same time relaxes the 

 scapular tendons and removes 

 them from the fossa. 3. The 

 elbow is raised until the arm 

 is parallel with the antero- 

 posterior axis of the body. 

 This rela.xes the anterior fibres 

 of the deltoid, the coraco- 

 brachialis, and the upper por- 

 tion of the capsule, and perhaps 

 widens the space between the 

 margins of the rent, although 

 no obstacle to reduction is usu- 

 ally met with there. The lower 

 portion of the capsule is still tense. 4. Rotation inward on this portion as a fulcrum 

 now moves the articular face of the head towards the comparatively free glenoid 

 cavity and relaxes the subscapularis ; as the elbow is then lowered in adduction the 

 lower capsular segment relaxes and the head re-enters through the rent by which it 

 originally emerged. These details can be worked out satisfactorily in experimental 

 luxations on the cadaver, and have apparently been demonstrated as to the main 

 points by Faraboeuf, Helferich, and others. 



Recurrent or "habitual dislocation" — i.e., dislocation occurring from trifling 

 causes, such as abduction of the arm — may be a remote result of the rupture or for- 

 cible separation of the tendons of the supra- and infraspinatus muscles from the cap- 

 sule of the joint, with rupture of the capsule at its upper portion, and the formation 

 of a free communication between the joint-cavity and that of the subcoracoid bursa 

 (Jossel, quoted by Stimson). It is, however, usually due to the injury to the capsule 

 and to the weakness of the shoulder muscles resulting from the original accident. 



Btirscs. — The large subacromial bursa and the subdeltoid bursa have been de- 

 scribed in relation to their possible enlargements (page 279). The subscapular bursa 



_j Axillary 



1 vessels 

 tS — Displaced 

 head of 

 humerus 



— — ^Axillary 

 vessels 



Pectoral is 

 major (cut) 



Deeper dissection of preceding subcoracoid luxation, showing 

 displacement of head of humerus and muscles involved. 



