Cyanide

What studies are showing us is that we really don't have a strong grip on the cause of many cases of chronic (or in this case, recurrent) back pain. Reasonable clinicians are starting to dismiss the discs as the cause of all back-pain (and really limitting it to the rare occassions where the discs are actually pressing on nerves).

But, that doesn't leave us with many convincing stories to tell. And, it leaves it up to us to create a compelling fiction to fill the gaps. I just so happen to have one of those "compelling fictions", good enough that I have even convinced myself that it may have validity.

Many back injuries will result in some muscle damage, either from the actual trauma or from the huge muscle contraction you exherted to try to avoid the trauma, pulling the muscle. When the muscle heals, well it heals with scar tissue instead of regenerated muscle fibres (muscle-building is a different process)

Scar tissue has a number of characteristics:

1) its never stronger than 70% the tissue architecture it replaced
2) It has no contractive function, its not a muscle
3) It shrinks over time. Look at any scar on your skin, if its large enough it will have a puckered edge, it shrank (you could easily find exceptions to this)
4) It is heavily innervated with pain nerve fibres.

So, what this leads to is a case where, the moment a scarred muscle starts to fatigue too much through heavy strain (twisting while carrying something) or through prolonged use (like sleeping in a bad position), it lengthens under load, surpassing the length of the scar, the weak scar starts to tear, sends off massive numbers of pain signals to the central nervous system. In a reflex loop, signals short circuit back to the muscles to tell them to go into a massive contraction to protect themselves under load and then this loop just keeps cycling on itself.....resulting in muscle spasm.

Finally, imagine all the other nerves that have to traverse from the spine to the periphery. They have to pass around and through all the structures in between point A and point B. Scars love to entangle anything near them as they develop. Its not unreasonable to think that some of these nerves could get caught up in the scar tissue, and thus get tethered down to nearby muscles. As the muscles go into spasm, they wrench on everything attached to them, including the nerves. Nerves don't work well under mechanical tension and thus the numbness would occur. You wouldn't feel the nerve geing stretched. But you would feel odd sensations/pain in the area of the body the nerve served. The brain doesn't know anything about where the nerve travels, only what regions it innervates.

Hope this is helpful..

Cheers

John