Development, ossification and variation of the pelvic bone

Development of the mesenchyme for the base of the os coxae takes place at the base of the growing limb bud from the end of the 5th week of development. Chondrification begins in the 6th week of development. The first ossification appears in the os ilium in the 9th week of development.

Ossification of the pelvic bone
There are 3 ossifying nuclei on the pelvic bone :


 * in os ilium (9th fetal week);
 * in os ischii (4th fetal month);
 * in the os pubis (4th–5th fetal month).

From these centers, ossification spreads to each bone separately. At birth, the entire area of ​​the acetabula, part of the front side of the os ilium, crista iliaca and also a strip along the lower edge of the os coxae are cartilaginous. The extensive cartilage on the outside of the acetabulum transitions to the inner surface of the bone, where it forms a Y shape and separates the os ilium, os ischii, and os pubis.

The ossifying os ischii and os pubis fuse with their shoulders in the 7th-8th. year of life. Ossification of the cartilago ypsiloformis starts from two secondary ossification centers in the acetabulum around the 12th-13th. year. One of these ossification centers, temporarily more prominent and separate, is called the acetabuli axis. This ossification is also the area of ​​growth of the entire acetabular landscape. The cartilaginous band on the lower edge of the os coxae begins to ossify above the tuber ischiadicum and the ossification spreads forward. At the same time, the ossification merges with the surrounding bone. This process takes place between 15-18 year of life. At this time, ossification and subsequent fusion with the surroundings in the cartilaginous rim of the crista iliaca also takes place.

Separate secondary apophyses appeared around the 15th–16th century. year they can appear in the tuberculum pubicum, in the spina iliaca anterior posterior, spina ischiadica and on the edge of the pubic symphysis. They merge with the surroundings after the 16th–18th century a year.

Variations of the pelvic bone
There are several minor shape variations on the pelvic bone:


 * 1) sulcus supraacetabularis as the starting point of the caput reflexum musculi recti femoris;
 * 2) tuberculum supraacetabulare – bump at the place of sulcus supraacetabularis;
 * 3) sulcus infraacetabularis – recess under the joint fossa, in the course of the obturatorius externus muscle;
 * 4) spina ischiadica of unusual shape, elongated, with facets for the formations attached to it;
 * 5) sulcus preauricularis – a non-constant vertical groove on the inner side of the bone in front of the facies auricularis, for connecting ligaments. anterior sacroiliac.

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 * Articulatio coxae