THE SUPERIOR EXTREMITY 



lateral aspect of the capsule there is a strong accessory 

 ligament, the costo-clavicular ligament, which lies behind the 

 origin of the subclavius muscle and passes upwards, back- 

 wards, and laterally from the first rib to the costal tubercle on 

 the lower surface of the clavicle. In the capsule itself there 

 are three thickened bands, an anterior, a posterior, and a 

 superior, and as some of the fibres of the latter pass from 

 one clavicle to the other, it is called the interclavicular 

 ligament. 



Joint capsule 

 Joint cavity 



Interarticular 

 ligament 



Joint cavity 



FIG. 1 8. Sterno-clavicular and Costo-sternal Joints. 



Anterior chondro- 

 sternal ligament 



Dissection. Pull the sternal head of the sterno-cleido- 

 mastoid muscle towards the median plane. Cut through the 

 anterior part of the capsule of the joint close to the sternum. 

 Pass the knife behind the capsule, avoiding the anterior jugular 

 vein, which runs laterally behind the upper border of the joint, 

 and detach the fibres of origin of the sterno-hyoid muscle which 

 spring from the back of the capsule. Cut through the posterior 

 ligament and pull the clavicle laterally. The articular disc is 

 now exposed. Detach it from the first rib ; then carry the knife 

 laterally below the clavicle and cut through the lower part of 

 the capsule and the costo-clavicular ligament. The clavicle 

 can now be displaced sufficiently upwards and laterally to bring 

 the whole of the brachial plexus into view. Before studying 

 the plexus, the dissector should note that behind the sterno- 



