The Role of Nucleus Pulposus in Spinal Shock Absorption

Can understanding the nucleus pulposus help in body positioning and prevention for individuals wanting to practice spinal hygiene and protect their discs from injury?

Nucleus Pulposus

The spinal discs are located between the spine’s vertebrae and are the body’s natural impact and shock absorbers. Within the disc is the nucleus pulposus, which plays a major role in providing the spine with shock absorption during movement. (Zhou Z. et al., 2014) The discs have a tough outer portion and a soft inner core. They are the:

Annulus Fibrosus

• The annulus fibrosus is the outer portion of the disc.(Nosikova, Y. S. et al., 2012)
• It forms the tough circular exterior and comprises concentric sheets of collagen fibers or lamellae surrounding the inner core.
• It has cartilaginous endplates that firmly attach to the vertebrae above and below.

Nucleus Pulposus

• The nucleus pulposus is the inner core soft filling of the discs.
• It contains a network of fibers suspended in a mucoprotein gel with a water base to maintain strength and pliability.
• The near-liquid consistency makes it responsive to movement to handle the body’s axial load.
• It helps maintain spinal suspension to prevent pressure on the bones and prevent bone-to-bone contact, reducing the potential for injuries and pain.

Shock Absorber

Each intervertebral disc is a shock-absorbing cushion, with the nucleus pulposus providing shock-absorbing properties (Zhou Z. et al., 2014). The intervertebral discs move as the body moves. For example, when arching the back, the disc moves forward slightly, and when twisting, the disc twists as well.

Spinal Action

The intervertebral disc supports spinal movements. When bending, twisting, arching, or tilting the spine, the nucleus pulposus swivels to accommodate these actions. These repeated spinal actions, which occur throughout the day and night, contribute to shifting positions while sitting, working, playing sports, carrying groceries, performing house chores, etc. An example is bending forward to pick something up. This action involves forward spinal flexion, which is bending the spine forward, flattening, or rounding. When bending using flexion, the spinal bones come closer together, pushing the nucleus pulposus toward the back.

Injuries

The disc can be pushed too far back with persistent or excessive spinal flexion. If the fibers of the annulus fibrosus become weak, they can tear, causing the nucleus pulposus to leak out and disc herniation. Generally, the nucleus pulposus will leak to the side and back; however, this corresponds to the location of the very sensitive nerve root/s with which it can come into contact, causing pain and other symptoms. The most common causes of disc herniation are degenerative wear and tear changes of the disc and trauma. Disc degeneration occurs as the body ages; it weakens the annulus fibers, allowing the nucleus pulposus to distend, bulge, or herniate.

Aging

Disc degeneration occurs with age but can also occur with injuries to the area. In young individuals, the nucleus pulposus is mostly water. For this age group, a herniation from trauma is more likely than in older individuals. (Ucar, D. et al., 2021) But as the body ages, the discs, especially the nucleus pulposus, begin to dry out. This dehydration leads to a significant loss of disc height. (UCLA Health, 2024) By age 60 or 70, the discs may be composed entirely of fiber, which can cause the shock absorption function not to work and disappear.

Chiropractic therapy is among the more conservative treatment options for a herniated disc and may be tried first before proceeding with more invasive treatments. Injury Medical Chiropractic and Functional Medicine Clinic works with primary healthcare providers and specialists to develop an optimal health and wellness solution that fully benefits the individual to get back to normal.

The Science of Functional Healing

References

Zhou, Z., Gao, M., Wei, F., Liang, J., Deng, W., Dai, X., Zhou, G., & Zou, X. (2014). Shock absorbing function study on denucleated intervertebral disc with or without hydrogel injection through static and dynamic biomechanical tests in vitro. BioMed research international, 2014, 461724. doi.org/10.1155/2014/461724

Nosikova, Y. S., Santerre, J. P., Grynpas, M., Gibson, G., & Kandel, R. A. (2012). Characterization of the annulus fibrosus-vertebral body interface: identification of new structural features. Journal of anatomy, 221(6), 577–589. doi.org/10.1111/j.1469-7580.2012.01537.x

Ucar, D., Duman, S., Bayram, Y., & Ucar, B. Y. (2021). Extruded disc herniations are experienced earlier by inactive young people in the high-tech gaming era. Journal of medicine and life, 14(3), 402–407. doi.org/10.25122/jml-2021-1059

UCLA Health. (2024). Degenerative disc disease (Conditions Treated, Issue. www.uclahealth.org/medical-services/neurosurgery/conditions-treated/degenerative-disc-disease