The next problem can occur when the nucleus pulposus starts to ?break through? the rings of the annulus fibrosis. This is what is usually termed as a disk herniation. Not all herniations cause pain. It depends upon whether or not the part of the annulus which ?sticks out? actually touches a nerve group or not. Even then, not all nerves are pain nerves, which we shall look at later in another post.
The final type of important disk injury is known as SEQUESTRATION. This can be quite serious. When this occurs, part of the nucleus pulposus actually breaks through the outer rings of the annulus fibrosis and leaves the disk. There are chemicals in the nucleus pulposus material which can be highly irritating to spinal nerves.
We spoke earlier about having a curve of a particular ?size? in your neck. By having this curve, the effects of pressure on your disks are minimized, and very importantly, the foramen ( or nerve exit hole ) is the optimum size to allow movement of the neck in all normal directions with minimal contact between the nerves coming out of the spine and the bones that make up the foramen ( ?half a hole? from the upper vertebra and ?half a hole? from the lower one ). This is a very important concept.
Here is a fact: the vast majority of people who have spent five years or more working with laptops do not have the correct curvature in their necks. I have seen hundreds of x-rays from IT workers, office workers etc , showing almost vertically straight bone structures in their necks. It must be remembered that the nerves leading to your hands and fingers and arms come out of these foramen holes in your neck. If that nerve is impinged by the bones of the neck, then it may cause pain, not only in the neck itself, but may be REFERRED to the arms, hands or fingers. Nerves are complex entities and I?ll put a separate post up about this later. For a few lucky ones, no problems will occur, due to them having been born with larger than normal foramen. However, for many, a slew of problems can and do occur. More on that later.
The average human head weighs about 8 to 12 pounds. Depending on the type, that?s about the weight of a bowling bowl. To get an idea of that weight ( if you?re feeling strong and have no arm/shoulder issues ), either pick up a bowling ball and hold it for ten minutes or get a bag and fill it with, say 10 one pound cans of soup, or a weight at the gym. Stand and hold that weight by your side for ten minutes. For most people, that will start to get uncomfortable pretty soon, but not unbearable. Now, start to put your arm out away from your body and repeat the experiment. For most people, within a minute or so, that is going to get very uncomfortable indeed. But why ? Did we suddenly increase the weight of the soup cans or bowling bowl by moving them away from our bodies ? No, that did not happen. So what has caused this increase in stress on our arms and shoulders ? The ?item? responsible is known as a TURNING MOMENT or TM. Nearly all engineers are familiar with this concept, yet it almost a complete mystery to most doctors and many therapists.
Imagine that you are changing a tire on your car. You go into the boot/trunk and take out the long nut remover shown in Figure 4 of the worked examples in the following weblink:
The car is fairly new and you are able to remove the nuts pretty easily. Time goes by and you have a rental car, same type and age as the first vehicle. You get a flat in the middle of nowhere. No problem. You open up the trunk, pull out the spare tire, and??no tire iron. The only thing you find is a six inch spanner/wrench. After three hours of cursing and sweating, you finally get the nuts off. Why was this so much effort ? You had to use much more physical, brute strength in the second case, compared with the first. Again, it boils down to turning moments, or in this case, since we dealing with a circular motion, what is called torque.
A turning moment is given by the product of force times distance. In order to remove the nuts, we preferably need a ?long distance? ( the distance from one end of the tire iron to the other ) and a small or moderate force. This is what we had in the first case. The amount of torque required to remove the nuts was X pound-feet.
In the second case, the distance from one end of the wrench to the other was very small in comparison with the first case. In order to achieve the same amount of torque ( X pound-feet ), necessary for removing the nuts, we had to apply more physical force so that the product of force times distance was the same in both cases.
Muscles ?feel? turning moment or torque. If you hold the bowling ball or weight close to your body, the distance between the weight and the FULCRUM ( or point around which rotation takes place ) is fairly small. However, when we held the weight out a distance away from our bodies, the weight remained the same as before, but the turning moment or torque ( torque refers to movement in a circular manner ) has increased as the distance increases.
Now we need to apply the same principles to our heads. When everything is completely ?normal?, our necks have an exact curve, neither too shallow nor too deep. The foramen holes are optimized in size such that when we bend over, turn and twist our necks, the bones of the vertebrae that make up the variable sized hole do not press against the nerves that exit from there. Most importantly, the muscles of the neck are nice and relaxed. The ones at the front have the same tension as the ones at the back. No bone spurs have formed, as the body does not sense any instability.
Take a good look at the people around in your office, at home and on the street over the next week. Only focus on their head and shoulders. When a head is positioned normally, the midline of the ear should pass down around about the middle of the shoulder. Stand sideways by the mirror, relaxed and with hands by your sides. Look out the side of your eye. Don?t try to stand erect, just stand completely at ease. Is your ear lined up with the middle of your shoulder or do you look like Mr Burns from the Simpsons ? Who do you most resemble in the following ?
Why is this important ?
Multiple reasons. Firstly, the center of gravity of your body should pass down just about to the front of your ankles. That way ( assuming everything else down the chain?head to toes, is as it should be ), you are balanced. Your weight is on your heels where it should be.
?My poor feet?I?ve been on them all day?they?re killing me?.
Must it be old age ?
Why is that Kalahari bushmen can walk nearly fifty miles a day over rough terrain barefoot at the age of 80 ? Something doesn?t compute. More on that later.
I can almost guarantee you that in a metropolitan area, very few people have their heads lined up as mentioned above. Some will have their heads so far forward that their bodies have become bent and they use walkers to get around. We have all been to the supermarket and seen that. Take a look at teenagers, especially at home, playing video games. Teenage spinal surgeries have increased dramatically over the last few years.
The problem is mainly our western lifestyle, and computers play a huge role in this.
We?ll take a look at how muscles work in the next post.