The pelvic spine consists of the sacrum and coccyx. These regions are called the cervical spine, thoracic spine, lumbar spine, sacrum, and coccyx. Together with the sacrum and coccyx, the hip bones form the pelvis. The body of ilium forms the sacroiliac joint with the sacrum. It extends over the lower part of the posterior surface of the sacrum and coccyx. The lumbar cistern extends into the sacrum upto S2 vertebra. The vertebrae of the sacrum and coccyx are usually fused and unable to move independently. Less common are fractures to the femur, pelvis, and sacrum. The iliocostalis originates from the sacrum, erector spinae aponeurosis, and iliac crest. Because the sacrum and coccyx are fused, they are not often used to provide location. It consists of a sacrum of five vertebrae, and two ilia. The three vertebrae of the sacrum are short and flat. At least 20 vertebrae formed the neck and back in front of the sacrum. The dorsal surface of the sacrum is convex and narrower than the pelvic surface. It consists of a sacrum connected to two ilia.