114 CLINICAL APPLIED ANATOMY. 



the cartilage of the first rib, which costal cartilage lies immediately 

 below the sternal end of the clavicle. Because of this relation- 

 ship, it will be readily understood that dislocation can only take 

 place in one of three directions forwards, backwards and upwards. 

 In all reduction may be easy, but retention in place difficult, owing 

 to the slight adaptability of the joint surfaces, the laceration of 

 ligaments and the weight of the upper extremity. 



Forward dislocation is the most frequent, being permitted by 

 the weakness of the anterior ligament, which is always torn, 

 together with part of the costo-clavicular or rhomboid ligament. 



Backward dislocation comes next. In this there is a greater 

 laceration of the capsule and usually a complete tearing away of 

 the rhomboid ligament. The sternal end of the clavicle slips 

 backward and lies behind the manubrium sterni and the origins 

 of the sterno-hyoid and sterno-thyroid muscles, and by posterior 

 pressure on the left side upon the oesophagus produces dysphagia, 

 by pushing the trachea over to the opposite side induces dyspnoea, 

 by direct pressure on the subclavian artery diminution or stoppage 

 of the radial pulse, and upon the innominate vein much congestion 

 of the parts from which this vessel drains the blood. 



Upward dislocation is rare, owing to the stability of the 

 rhomboid and the inter-clavicular ligaments, and of the inter- 

 articular fibro-cartilage. When it occurs all these three fibrous 

 structures are usually ruptured. 



Downward dislocation can only take place simultaneously with 

 a separation of the first costal cartilage. 



Dislocations at the Acromio-claYicular Joint. The joint 

 depends for its strength chiefly upon the coraco-clavicular 

 ligaments. The acromial end of the clavicle may be dislocated 

 upwards upon the acromion process, or downwards beneath it. 

 The former is the more usual owing to the plane of the joint 

 surface, which is from above downwards and inwards. In the 

 upward displacement there is a laceration of the slender capsule, 

 and more or less of the coraco-clavicular ligaments. Reduction 

 may be easy, but retention is difficult. 



Dislocations at the Shoulder- Joint. The shoulder- joint is the 



