STERNO-CLAVICULAR LIGA1WENTS. 135 



8. Articulation between the carpal bones. 



9. Carpo-metacarpal articulation. 



10. Metacarpo-phalangeal articulation. 



11. Articulation of the phalanges. 



1. Sterno-clavicular Articulation. The sterno-clavicular is an arthro- 

 dial articulation ; its ligaments are, 



Anterior sterno-clavicular, 



Posterior sterno-clavicular, 



Inter-clavicular, 



Costo-clavicular (rhomboid), 



Interarticular fibro-cartilage, 

 Two synovial membranes. 



The anterior sterno-clavicular ligament is a broad ligamentous 

 layer, extending obliquely downwards and forwards, and covering the 

 anterior aspect of the articulation. This ligament is in relation by its 

 anterior surface with the integument and with the sternal origin of the 

 sterno-mastoid muscle ; and behind with the interarticular fibro-carti- 

 lage and synovial membranes. 



The posterior sterno-clavicular ligament is a broad fasciculus, cover- 

 ing the posterior surface of the articulation. It is in relation by its 

 anterior surface with the interarticular fibro-cartilage and synovial 

 membranes, and behind with the sterno-hyoid muscle. 



The two ligaments are continuous at the upper and lower part of 

 the articulation, so as to form a complete capsule around the joint. 



The inter-clavicular ligament is a cord-like band which crosses from 

 the extremity of one clavicle to the other, and is closely connected 

 with the upper border of the sternum. It is separated by areolar 

 tissue from the sterno-thyroid muscles. 



The costo-clavicular ligament (rhomboid) is a thick fasciculus of 

 fibres, connecting the sternal extremity of the clavicle with the cartilage 

 of the first rib. It is situated obliquely between the rib and the 

 under surface of the clavicle. It is in relation in front with the tendon 

 of origin of the subclavius muscle, and behind with the subclavian 

 vein. 



Actions. The movements of the sterno-clavicular articulation, are a 

 gliding movement of the fibro-cartilage with the clavicle upon the arti- 

 cular surface of the sternum in the directions forwards, backwards, up- 

 wards, and downwards ; and circumduction. This articulation is the 

 centre of the movements of the shoulder. 



It is the rupture of the rhomboid ligament in dislocation of the ster- 

 nal end of the clavicle that gives rise to the deformity peculiar to this 

 accident. 



The interarticular fibro-cartilage is nearlv circular in form, and 

 thicker at the edges than in the centre. It is attached above to the 

 clavicle ; below to the cartilage of the first rib ; and throughout the 

 rest of its circumference to the anterior and posterior sterno-clavicular 



