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Quote:

Originally Posted by Leesa (Post 931920)

Hey -- You answered someone's questions about their MRI, and now I have a question for you. But first, you said that a "spondy is due to a bilateral crack in the pars which disengages the vertebral body from the neural arch and allows the vertebral body to slide forward."

Well, when they do a laminectomy, they either remove the arch, or disengage the vertebral body from it (I'm not sure which but I know it's one or the other), so wouldn't that automatically make someone who's had a laminectomy become a spondy?? Seems like that would CAUSE the problem.

I'm confused. :confused: Can you explain it to me??? And of course in terms that this blonde can understand? ;) Thanks. Lee

Hi Leesa,

Sorry, been out of town for the last 4 days. Yes, I did describe one of the four types of spondys; one with bilateral pars interuption. It's hard to describe without a diagram of consecutive articulated vertebra, but if you can get hold of a side and top view, it would help a lot!

While the posterior joints (facets) do not take much more than collectively about 30% axial loading, they are paramount in determining the direction in which the vertebra slide thru flexion and extension. To a considerable degree, they also limit the ability of the superior vertebra to slide forward on the inferior vertebra as they sort of lock the upper vertebra to the lower one in a dynamic way. The lamina (Rt and Lt) is the part of the neural arch, rearward to the facets while the right and left pars is the portion of the neural arch directly in front of the facets. So when the lamina are removed (for like a decompression of central stenosis), the facets are still intact and still attached to the vertabral body via the pars and continue to do their job. Questionable mild stability loss may occur, or not, because the ligamentum flavum (vertical ligaments that go from one lamina to another above and below) are also removed along with other postreior midline soft tissue and bony structures. In a spondy where there is spondylolysis or a "crack" in both pars, that occurs in front of the facets so there is a strucural loss of integrity that disengages the posterior from the anterior elements and then allows the upper vertebral body to slide forwards more or less on the lower one. The remaining essense of anterior stability then lies mostly upon the disc and ligamentous structures (ALL, PLL). Whether or not someone has pain from this is an entirely different question as there are Grade I-II spondys that are disabling and there are documented Grade III-IV (bigger and worse) that were incidentally found on x-rays done for other reasons than low back pain.