If you read my last blog post you know that I recently attended the Clinical Neurodynamics course with Michael Shacklock. One of the most interesting bits of discussion was his research and findings with lumbar foramen biomechanics and it's relationship to the lumbar nerve root. I've asked permission from him to write this blog post as this is part of the course and he has graciously permitted this.
For the longest time we assumed the foramen in the lumbar spine was doing what the disc did. This is no longer the case. The therapy approach Mckenzie has a large component of extension to drive the disc forward. This has been shown in MRI to be true. But for the disc to be driven forward, the posterior annulus must essentially spread or get larger to help drive the nucleus forward. So as this spreads, the foramen actually gets smaller.
So, going forward also does the exact opposite. As the spine bends into flexion the discs nucleus is pushed back. The annulus gets smaller. The foramen increases in size. A larger foramen is created. With the larger foramen comes 5 positive and tested outcomes.
1. The foramen area increases between 15-40%
2. Pressure on the nerve decreases 30-40%
3. Size of the nerve root increases. (from the reduction of the pressure)
4. Electrophysiology of the nerve improves. Strength of the contraction is better.
5. Pain has decreased.
Essentially the lumbar nerve roots and lumbar discs have opposite biomechanics. This doesn't mean the Mckenzie approach is wrong. It just means different techniques for different times It shows how some approaches such as PRI with their flexion based activities in my opinion give relief to some peoples back pain.
It reinforces to me some very important concepts like Functional Range Conditionings approach to having segmental control of the lumbar spine. How can you ultimately take pressure of a nerve root if you can't flex the lumbar spine segmentally?
They are showing that the same spine in a standing MRI with disc bulges go away essentially to the point you can't tell the disc has a bulge when the individual goes into flexion. This doesn't mean flex a disc patient that is in pain. What it does mean is perhaps the person that has fear based apprehensions to flexion because of a prognosis of disc bulge can be reeducated.
Again, there are some really important points to take away on how to use different movements at different times. Assess what you want to happen and use movement to help facilitate the right healing environment the body needs at the time.
Thanks again to Michael Shacklock for letting me share this. I can't recommend Clinical Neurodynamics enough for health practitioners out there.