The Development of the Pelvis

Abstract

Each hemipelvis develops from one cartilaginous anlage. According to Adair [1] cartilage formation inside the blastemic condensation of the pelvis starts at more than one site. Our material does not support this observation. At 8 weeks a single cartilaginous anlage is well seen (Fig. 11.3), with no transitional zone between the ilium, the ischium, and the pubis. This is evident in sections through the acetabulum (Fig. 11.7 b). In our material, evidence of ossification is first observed in the ilium where a periosteal direct bone formation is seen at 9½ weeks (Fig. 11.4). Shortly thereafter the area of degenerating chondrocytes (Streeter phase 5) in the middle of the ilium is the site of cellular and vascular invasion. This marks the beginning of the first phase of enchondral bone formation, a process well known in long bones (see Chap. 2). Gardner [5] also observed the beginning of ossification of the ilium at 9 weeks. The anterior superior iliac spine is said to develop at the end of the 3rd month [8]. The pubis starts to ossify around the 12th week and the ischium around the 15th week [5]. Ossification of ilium and ischium is seen in Chap. 12, Fig. 12.15.