472 ABDOMEN 



sacral canal, proceeds downwards upon the posterior aspect 

 of the coccyx. The posterior ligament is much the stronger 

 of the two. The sacral and coccygeal cornua are united by 

 fibrous bands. Other fibrous bands connect the lateral 

 angles of the sacrum and the transverse processes of the first 

 piece of the coccyx. 



As regards the coccygeal joints (when such exist), the union 

 of the different segments of the bone is brought about by 

 intervening fibro-cartilaginous discs and anterior and posterior 

 ligaments. 



Sacro-iliac Articulation. The sacrum is wedged in between 

 the two hip bones, and is held fast in that position by the 

 sinuous form of the opposed articular surfaces, and by the 

 strong ligaments which pass between the bones. The 

 ligaments are : 



1. Anterior sacro-iliac. 3. Sacro-tuberous. 



2. Posterior sacro-iliac. 4. Sacro-spinous. 



(a) Long posterior sacro-iliac. 



(b) Short posterior sacro-iliac. 



(c) Interosseous sacro-iliac. 



Ligamentum Sacroiliacum Anterius. The anterior sacro- 

 iliac ligament is by no means strong. It is composed of a 

 series of short fibres stretching across the front of the joint, 

 and connecting the bones anteriorly. 



Ligamentum Sacroiliacum Posterius Longum. The long 

 posterior sacro-iliac ligament is fixed, above, to the posterior 

 superior spine of the ilium ; whilst, inferiorly, it is inserted 

 into the third tubercle on the posterior surface of the 

 lateral mass of the sacrum. It lies posterior to the inter- 

 osseous ligament. 



Ligamentum Sacroiliacum Posterius Breve. The short 

 posterior sacro-iliac ligament also lies behind the interosseous 

 ligament, and is a short band of fibres which extends from 

 the posterior superior spine of the ilium to the back of the 

 sacrum. 



Ligamentum Sacroiliacum Interosseum. The interosseous 

 sacro-iliac ligament is exceedingly strong. It consists of fibrous 

 bands which connect the rough surface on the lateral part of 

 the posterior aspect of the sacrum with a corresponding rough 

 surface on the ilium, behind the auricular surface. Upon 

 the interosseus sacro-iliac ligaments the strength of the articu- 

 lation chiefly depends. Since the sacrum narrows towards its 



