The intervertebral disc is one of the more common things that we treat here at Tulsa Spine and Rehab. Just like to… As the name implies, intervertebral, it sits between two vertebrae. I have a model of the low back, or the lumbar spine, three vertebrae. The disc is the spongy thing in between the vertebrae. And I’d like to touch on a few things. We’re going to talk about the anatomy quickly, to give you a sense of what makes it up. Innervation, I think that’s very important because it causes pain many times. Nutrition, how we get the good stuff in and the bad stuff out. And then lastly, we’ll touch quickly on injuries and how we diagnose those types of disc injuries. Back on the anatomy, the disc serves a couple purposes here. It’s a ligament, so it actually will provide support and hold the vertebra together, like a ligament holds two bones together.
This disc is going to serve the same purpose. Also, it serves as a shock absorber. Think about a nice thick marshmallow. If we were to push on that marshmallow, it provides support on those structures on either side. A couple very important things. It not only is responsible for holding the vertebra together and providing support, think about providing space and shock absorption between the two vertebrae. It’s almost shaped, if we’re looking down on it, like a kidney, so like a kidney beam would look. It’s oval with a little indention and so forth. On the outside, there’s something called the annulus fibrosis. And so, that’s a big fancy word. It’s made up of a lot of collagen. Think about collagen, it provides a lot of tensile strength, cartilaginous. It holds everything in the middle.
The middle of that disc is called the nucleus pulposus, another big fancy words. We’ve got the fibrosis on the outside, very tight tensile strength, holding everything in the middle, and then we have this gelatinous nucleus pulposus. In the middle of all that, there’s a fibrous disc, as the name applies as well. Actually, the disc is made up of about 77% water, so hydration is so important to the disc, and we’ll get into that here in just a minute with nutrition. But essentially, we have these proteins, collagen. We have something else called proteoglycans, it’s another protein that actually binds the water within that disc. We’ve got this tensile structure that holds everything thing in, and then we’ve got this kind of jelly fluid surface made up of, predominantly, water. And then that cartilaginous disc in the middle. That’s just a brief overview of what the anatomy, the functional anatomy, of the disc is.
Secondly, innervation. Now, innervation simply means innervation or nerves to that area, just like I might have innervation to my forearm or my shoulder. If there was an injury, pain signals are going to be sent to my brain so forth. The same thing goes on with the disc. The disc is highly innervated on the outside. We talked about that outer ring or so forth. We have a fair amount of innervation, or nerves, that sit on the outside of that. Unfortunately, many of you may have heard of degenerative disc disease or joint disease. Essentially, what happens is, when that disc starts to shrink, or dry out, it loses some of that tensile strength, or some of that stability, on the outside. As that happens, those nerves have a tendency to grow to the inside of the annulus fibrosis, or the disc, and they get into that jelly substance in the middle. That’s why disc can injuries can be very, very painful. Obviously, it’s highly innervated. If there’s disruption to those nerves, it’s going to create a fair amount of pain. That’s why disc injuries, like I said, can be so uncomfortable.
Nutrition. Like most of… We get nutrition through our food and what we put in our mouths. The problem with the disc, it’s highly avascular. And what that means is there’s limited blood supply. As there’s limited blood supply, it’s tough to get the good stuff in, the food in, if you will, and the waste out. The disc relies on something called diffusion. Think about a cell, fluid travels in the good stuff into the cell, and then out of the cell. And so, it actually receives its nutrition from the bone above and below. The problem is, when we suffer from these degenerative conditions, we have something called desiccation, another fancy word. It means drying out. And so, the disc starts to dry out and shrink. It’s tough to get the fluid in and the waste out.
That’s why, as the disc degenerates, and so forth, and becomes more thin and hard, that process may speed up, because it’s tough for diffusion to take place. Also, there’s something called this diurnal of phenomenon, which means when we go to bed at night, everything has a chance to rehydrate, if you will. As I lay down and I’m in a non-weight bedroom position, that disc, that’s typically very full of water, starts to fill back up. Unfortunately, when I wake up in the morning, I get up gravity, starts to work against me, and I lose a lot of that water throughout the day. I think it’s said that disc can lose almost 25% of its shape throughout the day, just from daily activity and gravity.
That’s why motion is so important throughout the day to maintain that diffusion and that nutrition to the disc itself. Injuries and diagnosis, disc herniations, disc bulges, degenerative disc diseases, these are all common issues that we see here at the clinic. Also, this degenerative joint disease is something that can predispose, or comes before, some of these herniations and bulges. And simply, like the name states, it starts to move or bulge. It can put pressure on a nerve, potentially creates some form of sciatica down the leg.
Diagnostically, the physical exam is a good way to determine if there is potentially a disc problem. Then ultimately, MRI, or magnetic resonance imaging, is the most reliable tool to determine if there is a disc injury, and then to what degree. To review, disc injuries are one of the more common things that we see in here in the clinic. Conservative care, many times, is a good option for disc injuries. Otherwise, we might want to make a referral out. But I always encourage you, if you are somewhat fearful or if you have a history of some type of disc injuries in your family, or previous disc injuries yourself, it’s always important to get checked out.