Protecting Your Spine

One of the most common, immediate causes of low back pain involves injury to the intervertebral disc (IVD). The IVD is a connective tissue structure interposed between 2 spinal vertebrae.  This structure functions to attenuate spinal loading or absorb shock. IVD’s exist throughout the spine, but tend to cause more problems in the lower back compared to other spinal regions. The disc has 2 basic components: the outer annular fibers (annulus fibrosis), and the inner nucleus pulposus. The nucleus pulposus (NP) has more water content relative to the annulus fibrosis, making the NP more subject to pressure dynamics. For example, when you bend forward, the front or anterior portion of the disc is compressed, forcing the NP portion of the disc backward or posterior.

Expanding on this concept, when you assume positions of spinal flexion for prolonged periods of time, the pressure dynamic results in a posterior migration of the NP. This stretches the posterior annular fibers and over time and can weaken the annulus fibrosis. This sets the stage for disc injury.

Discs are injured primarily by either repetitive trunk flexion movements, or by combined bending and lifting movements. (Lifting heavy loads increases the pressure within the disc, and adds to the stress on the disc.) The term used to describe the resultant injury is disc herniation. A disc herniation is a focal tear in the annulus fibrosis, which allows the NP to protrude. The protrusion usually occurs in the posterior region of the vertebral unit, and can cause either local inflammation and local pain, or compression of the spinal nerve, which results in leg pain.

It is important to note that most disc injuries occur to discs that are already weakened through exposure to abnormal loading, such as prolonged sitting in flexed postures.

Understanding how discs become injured is the first step toward prevention.  The following guidelines are well accepted and common sense preventative measures:

• Avoid sitting in flexed postures; try to maintain an arch in your lower back or use a lumbar roll
• Know your limits with regard to lifting – sometimes it is much better in the long run to get help or use an assistive device
• When you do lift, keep your spine neutral (not flexed or extended) and use your powerful hip extensor and other lower extremity muscles
• Avoid prolonged and repeated trunk flexion movements or postures and extend your back periodically to reverse the mechanical stresses on your spine
• Maintain good core muscle strength

Finally, if you do have a problem with your low back and think you have injured your disc, see your physical therapist!

Marcia Miller Spoto PT, DC, OCS