SACRO-VERTEBRAL ARTICULATIONS 



233 



The ilio-lumbar ligament (fig. 271) is a strong, dense, triangular ligament 

 connecting the fourth and fifth lumbar vertebrae with the iliac crest. 



It springs from the front surface of the transverse process of the fifth lumbar vertebra as 

 far as the body, by a strong fasciculus from the posterior surface of the process near the tip, 

 and also from the front surface and lower edge of the transverse process and pedicle of the fourth 

 lumbar vertebra, as far medialward as the body. Between these two lumbar vertebrae it is 

 inseparable from the intertransverse hgament. 



At its origin from the transverse process of the fifth lumbar vertebra it is closely inter- 

 woven with the sacro-lumbar ligament, and some of its fibres spread downward on to the body 

 of the fifth vertebra, while others ascend to the disc above. At the pelvis it is attached to the 

 inner lip of the crest of the ilium for about two inches (5 cm.). The highest fibres at the column 

 form the upper edge of the ligament at the pelvis, those which come from the posterior portion 

 of the transverse process of the fifth lumbar vertebra forming the lower, while the fibres from 

 the front of the same process pass nearly horizontally lateralward. Near the column the surfaces 



Fig. 271. — Anterior View of the Lic-vments between Vertebrae and Pelvis. 



Foramen for anterior primary branch of fourth 

 lumbar nerve 



Foramen for last 

 lumbar nerve 

 Intervertebral disc 

 between last lum- 

 bar and first sacral 

 vertebrae 



The ilio-lumbar 

 ligament 



The sacro-lumbar 

 ligament 



Superior sacro-iliac 

 ligament 



Anterior sacro-iliac 

 ligament 



Sacro-tuberous 

 ligament 



Sacro-spinous ligament 



look directly backward and forward, but at the ilium the ligament gets somewhat twisted, so 

 that the posterior surface looks a little upward, and the anterior looks a Uttle downward. 

 The anterior surface forms part of the posterior boundary of the major (false) pelvis, and over- 

 lies the upper part of the posterior sacro-ihac ligament; the posterior surface forms part of the 

 floor of the spinal groove, and gives origin to the multifidus muscle. Of the borders, the upper 

 is oblique, has the anterior lamella of the lumbar fascia attached to it, and gives origin to the 

 quadratus lumborum; the lower is horizontal, and is adjacent to the upper edge of the sacro- 

 lumbar hgament; whUe the medial is crescentic, and forms the lateral boundary of a foramen 

 through which the fourth lumbar nerve passes. 



The arterial supply is very free, and comes from the last lumbar, ilio-lumbar, and lateral 

 sacral. 



Xba^.ffiprve -supply is from the s^mr[|j^Tgtic. as well as from twigs from the fourth and fifth 

 lumbar nerves. ^^^^^i^^^^H^* 



Movements. — The angle formed by the sacrum with the spinal column is called the sacro- 

 vertebral angle. Th e pel vic inclination does not depend entirely upon this angle, but in great 

 part upon the obhquity of the coxal (innominate) bones to the sacrum, so that in males in whom 

 the average pelvic obhquity is a little greater, the average sacro-vertebral angle is considerably , 

 less than in females. 



The sacro-vertebral angle in the male shows that there is a greater and more sudden change 

 in direction at the sacro-vertebral union than in the female. A part of tliis change in direction 

 is due to the greater thickness in the anterior part of the intervertebral fibro-cartilage between 

 the last lumbar vertebra and the sacrum. Owing to the greater thickness of the interverteb ral_ 



