Sacral

Sacral refers to the sacrum, the large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx (tailbone).

Anatomy

The sacrum is curved upon itself and placed very obliquely. It is concave facing forwards, which allows it to contribute to the walls of the pelvic cavity. The base projects forward as the sacral promontory internally, and articulates with the last lumbar vertebra to form the promontory of sacrum. The apex is directed downward and articulates with the coccyx.

Function

The sacrum has three different surfaces which are the pelvic, dorsal and lateral surface. The pelvic surface is concave and forms the back part of the pelvic cavity. The dorsal surface is convex and gives attachment to a number of muscles. The lateral surface is broad above, but narrowed into a thin edge below.

Clinical significance

The sacrum plays a key role in supporting the weight of the upper body and transmitting it to the lower limbs. It also protects the spinal nerves that emerge from the sacral foramina. Conditions affecting the sacrum can lead to lower back pain, sciatica, or other symptoms depending on the severity and exact location of the issue.

See also

• Sacral vertebrae
• Sacral plexus
• Sacral hiatus
• Sacralization of the fifth lumbar vertebra