Sacrum

Description

Centered at the caudal end of the vertebral column, the female sacrum is highlighted between the right and left os coxae, with the coccyx articulating inferiorly at the sacrococcygeal joint. From the posterior perspective, the sacral base lies superior, continuous with L5 at the lumbosacral junction, while the apex points inferior toward the intergluteal cleft. The paired posterior sacral foramina sit lateral to the median sacral crest, and the broad auricular surfaces face laterally toward the sacroiliac joints. Orientation is clear. Posterior sacral anatomy matters because it is where surface landmarks guide both diagnosis and procedures: the median sacral crest and sacral hiatus (between the sacral cornua) direct caudal epidural access, while the foramina relate to the exiting dorsal rami of the sacral spinal nerves. Stress fractures, insufficiency fractures in osteoporotic patients, and traumatic transverse fractures often involve the sacral ala and can destabilize the pelvic ring, so understanding the relationship between the sacrum, ilium, and sacroiliac joint is not optional in orthopedic trauma. In pelvic pain and suspected sacroiliitis, this view helps connect the clinical exam to the bony constraints that transmit axial load from the spine into the lower limbs. Use this posterior skeleton view in gross anatomy and osteology teaching to anchor the sacrum within whole-body alignment, or in radiology and orthopedic texts when introducing pelvic ring mechanics before correlating to AP pelvis, inlet, outlet, and CT reconstructions. It also fits well in obstetrics and gynecology materials discussing sexual dimorphism of the pelvis, with the sacrum as a determinant of pelvic inlet and outlet dimensions. Anatomical accuracy verified by SciePro's Medical Advisory Board.