REGION OF (UPPER) ARM 39 



The Axillary (Circumflex) Nerve (p. 33) winds horizontally 

 round the surgical neck of the humerus in the quadrilateral 

 space, where it is in close relation to the dependent part of the 

 capsule of the shoulder- joint (p. 16). In this region it may be 

 injured by the pressure of a crutch, by the head of the humerus 

 in sub-glenoid dislocations, and by the fragments in fracture of 

 the surgical neck. The nerve supplies the teres minor and the 

 deltoid. It can be mapped out on the surface by a horizontal 

 line, which intersects the line drawn from the lateral border of 

 the acromion to the insertion of the deltoid, at the junction of 

 its proximal and middle thirds. The results of injury to the 

 axillary nerve are described on page 101. 



Surgical Approach to the Proximal Part of the 

 Humerus. In disease or injury of the Proximal Part of the 

 Shaft (or diaphysis) of the humerus, the best approach is 

 obtained by a long incision, parallel to the posterior border of 

 the deltoid (Stiles). When the muscle is undermined and 

 retracted, the quadrilateral space is exposed, and the large 

 cutaneous branch of the axillary nerve is seen passing forwards 

 round the edge of the deltoid. The quadrilateral space is bounded 

 above by the teres minor, below by the teres major, laterally 

 by the surgical neck of the humerus, and medially by the long 

 head of the triceps. Through it the axillary nerve and the 

 posterior circumflex vessels pass backwards in close relation to 

 the surgical neck of the humerus and the dependent part of the 

 capsule of the shoulder -joint. Anterior to the origin of the 

 lateral head of the triceps and above the insertion of the deltoid, 

 the humerus is uncovered by muscles and offers good access to 

 the surgeon. 



The proximal part of the diaphysis of the humerus may 

 be resected subperiosteally for tuberculous osteomyelitis. After 

 the periosteum has been elevated, the diaphysis need only be 

 divided distal to the disease, as the part to be resected may 

 then be wrenched out from its periosteal sheath. In this way 

 the epiphyseal cartilage is left attached to the epiphysis and 

 the joint cavity is not opened (Fig. 6). 



Below the teres major the Radial (musculo - spiral) nerve 

 lies on the long head of the triceps, and after supplying this 

 muscle, it enters the radial groove in company with the (superior) 

 profunda branch of the brachial artery. In the groove it supplies 

 the medial and lateral heads of the triceps between which it 

 lies, and it passes distally and laterally across the back of the 



3c 



