Hi Fuzzy,
Yours makes sense - when you say your current disc height is 12mm, and that is the exact heigh of the device.
But, not meaning to 'nit-pick' ... if your pre-op height was 4mm, and you gained 12mm, then it should be 16mm. But, I guess they removed the disc material, so you must have actually only gained 8mm ????
Most important though, is that you note that the new disc height is basically the same as your natural disc heights ... so that your nerve root probably wasnt stretched nearly as much as it was decompressed back to normal ... and ... your facets will be callibrated (so long as they had not already become hypertophic)
Here is an article that describes (obvious to some) this concept with disc height and the facets:
http://www.spineuniverse.com/article...sion-2389.html
...
If your disc thins and can't handle movement as effectively, then the facet joints can become overworked. Facet joints stabilize the spine by controlling movement, but when a disc loses height, the facet joints lose alignment and have to readjust their movement. They can become overworked because the disc isn't doing its part to control the spine's movement—that's a lot of pressure on the facets.
If the facet joints are overworked, then the cartilage can wear away. Cartilage is meant to protect the joint and make movement easier. However, it can degenerate, leading to more facet joint problems. Without cartilage, the facets can move too much; this is called overriding.
If the facet joints are overriding, then bone spurs can develop. Bone spurs are your body's way of trying to protect itself. These bony overgrowths, also called osteophytes, are meant to stop the facets' excessive movement. A side effect of bone spurs, though, is that they can pinch nerves as they grow into the area where the nerves are exiting the spine.