THE SHOULDER REGION 9 



inter-clavicular ligament, which stretches from clavicle to clavicle 

 across the upper surface of the capsule and dips down in the 

 centre to become attached to the jugular (supra-sternal) notch ; 

 (2) The costo-davicular (rhomboid) ligament, which connects the 

 under surface of the sternal extremity of the clavicle to the 

 upper surface of the first costal cartilage. 



Movements. The sterno-clavicular joint acts as a hinge 

 for the clavicle, so that when the acromial end of the bone is 

 elevated or depressed, carried forwards or backwards, the 

 sternal end passes in the opposite direction. In elevation or 

 depression of the point of the shoulder the sternal end of the 

 clavicle moves over the surface of the articular disc, but when 

 the shoulder is thrust forwards or backwards the disc moves 

 with the clavicle over the clavicular facet on the sternum. 

 Excessive upward movement of the shoulder is checked by the 

 tension of the costo - clavicular ligament, and the opposite 

 movement by the tension of the articular disc and the inter- 

 clavicular ligament. 



The anterior supra-clavicular (supra- sternal) nerves (C. 3 and 4) 

 supply the joint, and branches from the internal mammary and 

 the clavicular branch of the thoraco-acromial (thoracic axis) artery 

 anastomose around it. 



In Dislocations of the Joint the sternal end of the clavicle 

 usually passes forwards, tearing the anterior sterno-clavicular 

 ligament. The direction taken by the bone is said to be due 

 to the weakness of this ligament, but it is more probable that it 

 depends on the application of the force along the axis of the 

 clavicle. Though this dislocation is easy to reduce by pulling 

 the two shoulders backwards, it is difficult to retain the bones 

 in apposition owing to the normal obliquity of their articular 

 surfaces. 



Backward dislocation is rare, and is caused either by indirect force thrusting 

 the shoulder forwards, or by direct violence from in front at the sternal 

 end of the clavicle. In this injury the posterior sterno-clavicular ligament 

 is torn, and the clavicle passes backwards, downwards, and medially, and 

 may compress the innominate vein, the trachea, or on the left side, the 

 oesophagus. 



Dislocation upwards is especially resisted by the articular disc and the 

 inter-clavicular ligaments. When these ligaments are torn, the sternal 

 end of the clavicle passes into the jugular (supra-sternal) notch between the 

 sterno-mastoid anteriorly (p. 8) and the sterno-hyoid and sterno-thyreoid 

 posteriorly. 



The sterno-clavicular joint is not infrequently the seat of suppuration 

 in pyaemia. One or both compartments may be involved and the pus usually 

 perforates the anterior ligament. Should it perforate the posterior ligament, 



