Intervertebral Discs: Structure and Injury Prevention

Today I had the opportunity to do a wellness presentation for a group of employees at a moving company. When we do these wellness presentations we have a variety of topics that we can present on and we strive to find the most relevant topic for our audience. So, I’m sure it’s no surprise that today’s topic was physical stress related to proper lifting techniques and injury prevention. As most of us do some lifting throughout our lives or have at least heard somebody talk about “throwing out their back,” I figured it would be useful to explain what is happening with the discs in your back.

When lifting heavy objects, we put a massive load on the lower back and as a result the most commonly injured tissues are the intervertebral discs of the lumbar spine. These intervertebral discs are located between each vertebral body in your spine and therefore act like cushions between the bones. These discs have a unique structure that can be best explained by picturing a jelly donut.  The inside of the disc is made up of a soft material and the outside is made up of a thicker tissue that is layers of rings packed tightly on top of each other. The fibers of these rings are angled at 45-degrees with each ring alternating the direction that the fibers are running, creating X-like patterns. These alternating layers of rings become vital to the health of your discs.

Normal Disc                           Bulging Disc                            Herniated Disc

The angled orientation of these fibers makes the discs very prone to injury during any motion involving a bend, twist, and lift.  This is a classic movement that will injure a disc because when the spine rotates half of the ring layers will become stretched, while the other half become relaxed.  This puts the disc tissue itself in a compromised position.  Also, when we bend over and lift something heavy, a lot of pressure is put on our spine angled towards the back.  Imagine squeezing one end of that jelly donut and the pressure shifting the jelly toward the opposite side, that is what happens when we lift something.  So, combining the bend, twist, and lift increases the likelihood of that interior disc tissue (the jelly) from breaking through the ring layers that are not in their most stable position due to the rotation.  When the inner tissue of the disc starts breaking through those outer rings, you will form a disc bulge.  When the inner tissue breaks through the outermost ring layer and leaks past the boundary of the disc, that is now officially a disc herniation.

Let’s revisit another important component of the ring layers, which is their nerve supply.  The key with the nerve supply to the discs is that only the very outer rings have nerves that run directly to them.  This is important because your body cannot feel anything that a nerve doesn’t supply.  In the case of a disc injury, this is huge because that inner disc material may have already started breaking through the inner parts of the rings, but your body can’t tell it is happening because there are no nerves to that area.  It isn’t until the jelly breaks through the outside of the rings that the brain knows there is a problem, and at that point it is often too late.

Completely preventing disc injuries can be difficult, especially if your job entails lifting and carrying heavy furniture like the guys I presented to today.  However, with proper lifting mechanics and keeping the spine functioning, everyone stands a fighting chance at avoiding injury. If you’re job or lifestyle involves a lot of lifting, twisting, or repetitive motions we are happy to do an exam and X-rays to help identify if you may already be experiencing a disc issue.

Yours in Health, Dr. Alex

Project Wellness Company Madison, WI