198 



SURGICAL APPLIED ANATOMY. [Chap. xi. 



3. Subspinous. The head usually rests on 

 the - posterior surface of the neck of the scapula, the 

 groove of the anatomical neck of the humerus corre- 

 sponding to the posterior lip of the gleiioid fossa. 

 The head is thus placed beneath the acromion ; but it 



may be displaced still 

 farther back, and may 

 rest on the dorsum 

 scapulae, and beneath 

 the scapular spine 

 (Fig. 20). The sub- 

 scapularis tendon is 

 drawn right across the 

 glenoid fossa, and is 

 often torn from its 

 attachment. The head 

 pushes back the hinder 

 part of the deltoid, the 

 infraspinatus, and teres 

 minor muscles. These 

 latter cover the bone, 

 and are stretched over 



Fig. 20. Subspinous Dislocation of & Tne Supraspiliatus 



Humerus. j s tense, as is also the 



biceps, while the teres 



major and latissimus dorsi are relaxed. The great 

 pectoral is rendered unduly tense, and this serves 

 in part to explain the rotation inwards of the 

 humerus, and the adduction forwards, that are usually 

 observed, those movements being more or less un- 

 opposed. The circumflex nerve is often torn. 



In reducing dislocations, especially such as are of 

 long standing, serious damage may be inflicted on the 

 axillary structures. The axillary artery suffers most 

 frequently, the vein rarely , and the nerves still less 

 often. The artery, being placed externally, is apt to 

 contract adhesions to the soft parts covering the head 



