12 THE SUPERIOR EXTREMITY 



bone. Occasionally, the lateral fragment is displaced backwards 

 by direct violence from in front. In this case the transverse 

 scapular (supra-scapular) and transverse cervical (transversalis 

 colli) veins (p. 131) may be injured. 



Fracture of the acromial end of the shaft may occur between 

 the attachments of the two parts of the coraco-clavicular 

 ligament from direct violence, in which case there is little 

 displacement,, or it may occur lateral to the ligament, in which 

 case the lateral fragment tends to turn medially and forwards. 

 The point of the shoulder is rotated medially and sinks slightly. 



In children, fractures of the clavicle are usually of the 

 greenstick variety, as the bone is soft and its enveloping 

 periosteum is exceedingly strong. 



The Vertebro-Scapular Muscles. The Trapezius is described on 

 p. 6. 



The Levalor Scapulce is attached to the medial (superior) angle of the 

 scapula, by elevating which it helps to depress the point of the shoulder. 

 It is supplied by C. 3 and 4 (p. 130). 



The Rhomboid Minor and Major arise from the upper thoracic spines 

 and are inserted into the vertebral border of the scapula. They draw the 

 scapula medially, backwards and upwards. The dorsalis scapulae nerve 

 (nerve to the rhomboids) (C. 5) runs down along the vertebral border of the 

 scapula under cover of the three above-mentioned muscles. (The results of 

 injury to this nerve are described on p. 97.) It is accompanied by the 

 descending (posterior scapular) branch of the transverse cervical artery, 

 which anastomoses on the scapula with the subscapular (p. 34) and the 

 transverse scapular (supra-scapular) arteries (p. 143). 



The Scapula. Ossification begins in the fcetal scapula 

 during the second month. The most important secondary 

 centre forms the greater part of the coracoid process. It 

 appears during the first year and joins the body about the 

 eighteenth year. Cases of ununited coracoid epiphyses have 

 been recorded, but the condition is very rare. 



Two secondary centres appear about the tenth year to form 

 the acromion,, and join the spine of the scapula about twenty-five. 

 This epiphysis fails to fuse in 10 per cent of subjects, and the 

 condition is usually bilateral. The line of non-union is transverse 

 and is at right angles to the axis of the acromio-clavicular joint. 

 The acromion is generally attached to the spine by fibrous 

 tissue, but occasionally a complete joint is present. The presence 

 of a movable acromion, together with a history of injury to 

 the shoulder region, is apt to suggest a fracture. The 

 symmetrical character of ununited acromial epiphysis is of 

 great value in the differential diagnosis. 



