Anatomy of Sacrum
- upper end of sacrum, base of triangle, is directed forward & upward;
- in middle is upper surface of body of the first sacral vertebra;
- its anterior border forms the sacral promontory.
- it is concave & fairly smooth on its pelvic surface, & convex & irregular on its dorsal surface.
- consists of five fused vertebrae, is broadened proximally by fusion of large costal elements and transverse processes into heavy pars
lateralis on each side;
- pelvic side has 4 ridges marking lines of fusion of vertebrae;
- at ends of ridges are large pelvic sacral foramina through which ventral rami of sacral nerves emerge;
- on dorsal side, there are 4 converging grooves for sacral nerves about an inch lateral to median sacral crest (rudimentary fused spinous
- lateral to the sacral foramina are lateral sacral crests representing transverse processes;
- behind the body is large vertebral foramen leading into sacral canal.
- sacral canal is roofed by fused laminae of S1-S4;
- superior articular processes of sacrum are supported by short heavy pedicles;
- articular facets face medially and posteriorly.
- sacrum is situated between the two hip bones; upper, wider part of pars lateralis articulates with the ilium on each side.
Original Text by Clifford R. Wheeless, III, MD.
Last updated by Data Trace Staff on Monday, August 29, 2011 2:49 pm