328 A MANUAL OF ANATOMY 



Movements. — The movements at this joint are Umited, and are principally 

 of a gliding nature in an upward and downward, and forward and backward, 

 direction. 



The Ligaments of the Scapula. 



These are three in number — suprascapular, coraco- acromial, and 

 spino-glenoid. 



The suprascapular or transverse ligament extends from the upper 

 border of the scapula, internal to the suprascapular notch, to the root 

 of the coracoid process. It is thin and flat, and it bridges over the 

 notch, which it converts into a foramen. It usually gives origin to 

 some fibres of the posterior belly of the omo-hyoid, and the supra- 

 scapular nerve passes backwards beneath it and the suprascapular 

 artery over it. This ligament sometimes undergoes ossification. 



The coraco-acromial ligament, which is triangular, is attached by 

 its apex to the tip of the acromion process, and by its base to the 

 postero-external border of the coracoid process. Its superior 

 surface is covered by the deltoid, and the inferior surface overhangs 

 the shoulder-joint, the subacromial bursa intervening. The acro- 

 mion process, coraco-acromial ligament, and coracoid process form 

 the coraco-acromial arch, within which the head of the humerus 

 fits when the arm is abducted. The arch therefore forms an 

 auxiliary socket for the head of the bone. 



The spino-glenoid ligament consists of a few fibres which extend 

 from the outer border of the spine to the adjacent part of the margin 

 of the glenoid cavity. It arches over the suprascapular artery and 

 nerve as they pass through the great scapular notch on their way 

 to the infraspinous fossa. 



Movements of the Scapula. — These movements take place at 

 the acromio-clavicular joint, and are associated with movements 

 of the clavicle. They are of two kinds — namely, gliding and 

 rotation. 



Gliding Movements. — These take place upwards, downwards, out- 

 wards or forwards, and inwards or backwards. During their occur- 

 rence the scapula moves over the dorsal wall of the thorax in such 

 a manner as to describe the arc of a circle. The centre of this circle 

 corresponds to the sterno-clavicular joint, and the clavicle repre- 

 sents a ray of the circle. In the inward or bacl^ward movement the 

 base of the scapula is drawn towards the vertebral column, and in 

 the outward or forward movement the base is drawn away from the 

 vertebral column. 



Rotatory Movements. — Rotation takes place inwards and out- 

 wards. During internal rotation the acromion is elevated, the 

 superior angle is depressed, and the inferior angle moves slightly 

 outwards. In internal rotation the conoid ligament is tightened. 

 During external rotation the superior angle is elevated, the acromion 

 is depressed, and the inferior angle moves slightly inwards. In 

 external rotation the trapezoid ligament is tightened. 



