Tailbone (Sacral Spine)

The sacral spine is at the very end of the back, lower than the lumbar spine. There are two main bones of the sacral spine–the sacrum and the coccyx (tailbone)–both made of multiple fused bones. 

Sacral Spine Anatomy

The Sacrum

The sacrum is a wedge-shaped piece of bone directly below the lumbar spine. It is made of five fused vertebrae numbered s1 through s5. These five vertebrae are separate in children and young people. They begin to fuse in late adolescence and early adulthood and are usually fully fused by age 30.

The sacrum acts as the base of the spinal column, as well as the back “wall” of the pelvis. The iliac crests of the pelvis attach on the left and the right of the sacrum, forming the sacroiliac joints. The lumbosacral joint is where the bottom of the lumbar spine (l5) meets the top of the sacrum (s1).

The Coccyx

Below the sacrum is the coccyx, commonly known as the tailbone. The coccyx, like the sacrum, is a set of fused bones, though four bones make up the coccyx. It serves as an attachment point for a number of pelvic and hip tendons. Another main purpose is the bear weight while seated. 

Sacral Spine Conditions

The sacral spine is stable compared to other regions of the spine, and is somewhat protected due to its position relative to the hips and pelvis. The most common injury to the sacrum and the coccyx is a fracture due to a fall. Additionally, sciatica will often arise due to the pinching of nerve roots at the lumbosacral joint. The sacroiliac joints can become inflamed due to either too much or not enough range of motion. 

Sacral Spine Procedures

Fractures to the sacrum or the coccyx are rarely actively managed. Rest is usually the main form of treatment for one of these fractures, though decompression surgery may be required if nerves are affected. 

Sciatica treatment can include: 

  • Anti-inflammatory medications and injections
  • Physical therapy
  • Microdiscectomy
  • Laminectomy

If you are experiencing pelvic or hip pain, request an appointment at Edison Spine Surgeons. We will be able to determine if your pain is originating in the sacral spine, and we will develop a treatment plan that’s right for you. 

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