Solving Spinal Cord Physics for Scoliosis Research

[shwin]

Hey all, I'm doing research on scoliosis and one thing that gets me is understanding the physics behind a bow and arrow/steel beam. That is, if it is curved and held from one end (lengthwise), what is the best way to apply a force to straighten it out?

Also, what do you think is a more suitable model for a spine with scoliosis: a sine curve or a segment of a circle?

 

[FredGarvin]

That's a tough question with regards to the human body. The only way to straighten a curved beam is to constrain all degrees of freedom except the one you need to move in. I can't quite see doing that on a person without some kind of serious contraption.

When we have shafts that are bent, in some cases we do straighten them by heat and putting them in pure tension. However, I don't think that would be applicable for you either. I would tend to think that the tensile force in the direction of the spine would be one way to go. I believe that is what is attempted when a person is in traction.

 

[Danger]

Welcome to PF, Shwin.
I agree with Fred that it's almost impossible to equate scoliosis with situations that are encountered in normal mechanical devices. For one thing, the title of the thread is a bit misleading. It's the spinal column that you're concerned with, not the cord.
The construction and functioning of that column are far outside of most engineers' or physicists' experience and training. Most significantly, it isn't a solid structure by any means. Any sort of 'beam loading' equations won't work. You have a bunch of solid pieces connected by elastic fluid-filled sacs and several different muscular configurations. The closest mechanical devices that I can think of are 'snakebots' and Doc Ock's fictional arms, but even those have solid joints.
Biomechanics and maybe biophysics are what you need for this, not regular phyisics or engineering.
I certainly look forward to seeing the input of people in those fields.

 

[shwin]

Welcome to PF, Shwin.
I agree with Fred that it's almost impossible to equate scoliosis with situations that are encountered in normal mechanical devices. For one thing, the title of the thread is a bit misleading. It's the spinal column that you're concerned with, not the cord.
The construction and functioning of that column are far outside of most engineers' or physicists' experience and training. Most significantly, it isn't a solid structure by any means. Any sort of 'beam loading' equations won't work. You have a bunch of solid pieces connected by elastic fluid-filled sacs and several different muscular configurations. The closest mechanical devices that I can think of are 'snakebots' and Doc Ock's fictional arms, but even those have solid joints.
Biomechanics and maybe biophyics are what you need for this, not regular phyisics or engineering.
I certainly look forward to seeing the input of people in those fields.

Well I was thinking "spinal cord injury - physics "as the title but I guess my brain skipped that haha. And yes I am looking for the biomechanics to come out >.>

 

[Danger]

That's still a bit off-base, though. While scoliosis can cause a spinal cord injury, it isn't the result of one. Back to square one.

 

[Hacky]

The spine has static (bone, ligaments, discs...) and dynamic (muscle) stabilizers. Spinal cord injury, if high enough, can cause scoliosis due to paralysis of the muscles that support the spine (think of a radio tower supported by guide wires). However, most cases of scoliosis either have no known cause or are caused by severe degenerative changes in discs and facet joints (arthritis). These deformities can occur in multiple planes and involve rotational deformity, very complex. But you are reinventing the wheel, there is an enormous amount published about the biomechanics of scoliosis and even more published on mechanical constructs to correct scoliosis and maintain this correction. This is a huge business with more implants coming on the market every year.

If possible you can go to a medical library and find a book on biomechanics (of the spine) or a modern book on spine surgery. www.pubmed.gov will have more references on this topic than you would believe. You can search for "scoliosis and biomechanics" and "scoliosis and reconstruction", "scoliosis and implants" etc... But this will only give you the abstracts unless your library has electronic versions of journals.

Howard

 

[Danger]

Spinal cord injury, if high enough, can cause scoliosis due to paralysis of the muscles that support the spine (think of a radio tower supported by guide wires).

I stand corrected. Thanks, Howard.