Ligaments of Clavicle 225 



THE CLAVICLE AND SCAPULA 



The clavicle articulates with the first costal cartilage, and, through 

 the medium of a fibro-cartilaginous disc, with the sternum. Its inner 

 two-thirds are almost cylindrical, and are concave on the posterior 

 aspect, so that when the shoulder is lowered the subclavian vessels 

 and the brachial plexus may not be pressed against the first rib. 



The articulation between the clavicle and acromion forms the 

 shoulder ; the shoulder-joint is the articulation between the glenoid 

 cavity and humerus. 



The rounded end of the clavicle is so firmly held down to the 

 first costal cartilage by the rhomboid ligament that dislocation of the 

 sternal end is extremely rare. It may occur, however, on to the front 

 of the manubrium, upwards, or backwards. In the last case the end of 

 the bone might so press upon the trachea as to demand a partial 

 excision of the bone. It might also press upon the end of the internal 

 jugular or the beginning of the innomimate vein, which are close 

 behind it. 



The sterno- clavicular joint belongs to the class Arthrodia, and 

 its gliding movements are much increased by the presence of the 

 inter-articular fibro-cartilage which intervenes between the sternal 

 facet and the end of the clavicle. This disc effects, as part of its office, 

 the breaking of shocks transmitted by a fall upon the hand. Each 

 surface is covered by a synovial membrane, and these membranes 

 may join by a hole in the disc. The larger membrane is that between 

 the end of the clavicle and the disc, as it also lines the articulating 

 surfaces of the clavicle and the first costal cartilage. The joint is 

 enclosed by an anterior and a posterior ligament, and by superior fibres 

 (the inter-clavicular ligament] which run from clavicle to clavicle with 

 an intermediate connection with the supra-sternal notch. 



In front of the joint is the sternal origin of the sterno-mastoid, and 

 behind are the sterno-hyoid and thyroid. 



The rhomboid ligament is a strong band connecting the inner end 

 of the clavicle with the cartilage of the first rib ; it prevents extreme 

 elevation of the clavicle without a simultaneous effort at inspiration. 

 In front of it is the origin of the subclavius, and close behind it runs 

 the subclavian vein. 



The outer third is flat, and articulates with the acromion by an 

 oblique facet. Dislocation of this joint rarely occurs, because strong 

 ligaments ascending from the coracoid to the clavicle (conoid and 

 trapezoid) are a firm bond of union ; the slope of the facets renders 

 upward luxation of the clavicle the only one possible. As the bones are 

 subcutaneous, the diagnosis is easily made out, but, though it may be 



Q 



