4 THE SUPERIOR EXTREMITY 



are often very difficult to diagnose, owing to the depth of the 

 bone from the surface and to the bruising and effusion which 

 supervene. An increase in the antero-posterior diameter of 

 the greater tubercle can be determined by grasping that land- 

 mark between the fingers and thumb and comparing it with 

 the greater tubercle of the opposite side. It is very suggestive 

 of fracture in this part of the bone, but accurate diagnosis is 

 possible only by means of the X-rays. 



The lesser tubercle (small tuberosity) of the humerus points 

 directly forwards and lies one inch lateral to the coracoid process 

 and on a slightly lower plane. It also lies under cover of the 

 deltoid. On deep pressure over them, the tubercles can be 

 felt to slip from under the finger, if the humerus is rotated 

 alternately medially and laterally. Immediately to the lateral 

 side of the lesser tubercle lies the intertubercular sulcus (bicipital 

 groove) containing the long tendon of the biceps. This groove 

 corresponds to the lower two-thirds of a line three inches long, 

 drawn from the tip of the acromion down the arm in the axis 

 of the humerus. 



When the arm is by the side, the inferior margin of the 

 head of the humerus is easily palpated through the floor of the 

 axilla. As the arm is abducted, more of the head becomes 

 exposed to the examining finger, but it is less distinctly felt 

 owing to the tightening of the axillary fascia. 



Superficial Nerves. The skin of the shoulder region is 

 supplied in front by the descending branches of the cervical plexus 

 (C. 3 and 4). 



The anterior and middle supra-clavicular branches (supra- 

 sternal and supra-clavicular) extend down on to the chest wall 

 as far as the second intercostal space, where they are overlapped 

 by branches from the second intercostal nerve. This fact 

 explains the constant level of the anterior line of anesthesia in 

 fracture dislocations occurring between the fifth cervical and 

 second thoracic vertebrae, and also the referred pain sometimes 

 felt over the clavicle in Pott's disease of the third, fourth, and 

 fifth cervical vertebrae. Occasionally the supra-clavicular nerves 

 are involved in callus following fracture of the clavicle and cause 

 persistent neuralgia, which may radiate over the same side of 

 the head and neck. The posterior supra-clavicular (supra- 

 acromial) branches extend down for a short distance over the 

 deltoid, overlapping the cutaneous branches of the axillary 

 (circumflex) nerve (Fig. 2). 



