[jss]

annapurna,

Thank you so much for your thoughts. And I agree that the up and down pressures from my six mile run at lunch yesterday puts far more stress than SCUBA on the discs; at least where the stresses of axial compression are concerned.

My concern has to do with pressures pushing on the disc from the sides. Specifically, our intervertebral discs don't incur in daily activity the kind of stress they would from a hyperbaric chamber, someone choking us, or SCUBA diving; that is, there is no lateral stress into the center of the horizontal structure of the disc (as far as I am aware). My concern is, when under that type of increased pressure, will the polymer sheath that holds wear debris inside the disc separate from the top and bottom plates?

Spinal Kinetics has demonstrated in their testing that that structure won't fail under the stress of 3,000,000 axial compressions where each compression is equal to the magnitude of that experienced when running; (which makes me think that the empty space inside the sealed disc was filled with an inert gas). I want them to tell me how hard you have to push on the polymer sheath from the outside to induce a failure.

Make sense?