The sacrum is the triangle-shaped bone at the end of the spine between the lumbar spine and the tailbone. The sacral spine consists of five segments, S1 - S5, that together affect nerve communication to the lower portion of the body.
It is important to understand that the spinal cord does not extend beyond the lumbar spine. L2 is the lowest vertebral segment that contains spinal cord. After that point, nerve roots exit each of the remaining vertebral levels beyond the spinal cord.
Damage to the spine at the sacrum levels affects the nerve roots as follows:
- S1 affects the hips and groin area
- S2 affects the back of the thighs
- S3 affects the medial buttock area
- S4 & S5 affect the perineal area
Damage to the sacral spine is less common than other forms of spinal cord injuries. The sacral spine is also the least likely area for spinal nerves to become compressed. Some incomplete spinal injuries to this level are referred to as sacral sparing, as the motor function pathways are spared in the injury.
*Learn more about Sacral Sparing.
Injuries to the Sacral Spine
While there is no spinal cord in the sacral spine region, the sacral nerves actually originate in the lumbar spine. Damage done to the nerve roots in the lower lumbar spine and into the sacrum may have similar symptoms as spinal cord damage.
Patients with sacral nerve injuries may have symptoms on one or both sides of the body. Injuries to the sacral spine may leave the patient with some degree of function loss in the hips and/or legs. The patient will most likely be able to walk, and drive a car. An injury to the sacral spinal cord may leave the patient with little or no bladder or bowel control, however, the patient will be completely autonomous and have the ability to perform their own self-care.
The sacral region is home to the control center for pelvic organs such as the bladder, bowel, and sex organs. Sexual function is a concern, especially in men who experience sacral spinal nerve injuries. Men’s fertility may be affected with lumbar and/or sacral nerve injuries while a woman’s fertility is typically not affected.
Patients with injuries to the sacral nerve roots may experience:
- Lack of control of bowels or bladder
- Lower back pain
- Leg pain, which may radiate down the back of the leg(s)
- Sensory issues in the groin and buttocks area
The most common causes of spinal cord injuries to the sacrum are:
- Motor vehicle accidents
- Birth defects
Current treatments available for spinal cord patients with sacrum injuries are:
- Drugs: Non-steroidal anti-inflammatory (NSAID) drugs are used in treating spinal cord and nerve root injuries. The quicker these drugs are initiated after injury, the better the result for the patient by reducing inflammation around the spinal cord.
- Surgery: Surgical decompression of the nerves and fusion of the vertebrae are done to reduce pressure around the spinal nerves, and fixate the spinal column around the spinal cord injury.
- Therapy: Physical therapy is done to encourage strength in the areas that are affected by spinal cord damage, as well as to maintain function in the non-affected area. Occupational therapy helps patients to learn to function after spinal cord damage.
Damaging either the S1, S2, S3, S4, or S5 vertebrae should leave the patient fairly functional with some issues controlling bowel and bladder function. Patients with injuries to the sacrum typically live very normal lives. Some assistance may be needed for these patients, but most do well on their own.