In rare cases the right and left preacetabular blades fuse with each other above the spinous processes.
2
The preacetabular portion of the ilium is shorter than the posterior half.
3
The ventral inner margin of the preacetabular portion of the ilium is attached to the pre-sacral vertebrae, whilst the inner and dorsal margin of the postacetabular portion is attached to the primary sacral and the postsacral vertebrae.