anterior longitudinal ligament (cervical surgery question)

[paulam310]

Mark, when you state that the ligament is redundant, are you saying that the ALL is not necessary to have after adr because the structural strength of the adr makes up for its loss?

[rob_zzz]

Mark,

Thanks for the info - I've never really thought about it - but always assumed that disc material (from a non-degenerated disc) would be sinewy/strong and difficult to remove, and would provide assistance holding the vertebrae together. But I've never seen it except what they show on the surgery videos - so are you saying its more fibrous than I'm imagining and breaks down more easily and is unlikey to assist much in providing tension to hold the vertebrae together?

thanks,
Rob

[mmglobal]

Paula, when I say it is redundant, I mean that you can live without it (or at least without the portion that is compromised by the surgery.) The ADR does not add substantial strength, except as restoring the disc height retensions the other elements of the system. Note that these other elements are required for the stability of the prosthesis. That is why if instability is too great, you are not a candidate for ADR.

Rob, I do not know how much strength the disc nucleus adds to the system. (My 'lay' perception is that is is not a ssubstantial percentage... but I'm not sure what I base that on.) What I do know is that many patients with completely collapsed disc spaces still have stable systems. Also, even after the discectomy and when the ALL, PLL, anterior and posterior annulus have been resected; it is still very difficult to get the prostheses in. There is an incredible amount of tension on the system.

[paulam310]

Mark, thank you so much for that info. It is great to have someone so knowledgeable answer questions.

[sahuaro]

Ditto to Paula's note of thanks. I am also grateful to the members who can formulate and raise these questions.

[rob_zzz]

Wow that grays anatomy site's awesome (there was a link to it in the dated but useful topics post that harrison put up). The link below talks about the various ligaments (note they called 'discs' invertebral fibro cartillage).

http://www.bartleby.com/107/72.html

One extract from this section:

In extension, or movement backward, an exactly opposite disposition of the parts takes place. This movement is limited by the anterior longitudinal ligament, and by the approximation of the spinous processes. It is freest in the cervical region.

So from all of this information this is the conclusion I'm drawing: the anterior longitudinal ligament, as well as the disc are both of some importance in limiting overextension (and overrotation) of the neck - particularly the ALL, though it does appear that the spinous processes also work to prevent overextension by coming together. The facets would also contribute to preventing the neck from 'coming apart' during extension as would the whole mass of different muscles that attach different levels of the spine to each other (see this link: http://www.bartleby.com/107/illus389.html).

I suppose that there's a fair chance scar tissue would grow over the area where the missing ALL piece is(particularly if it was able to be sewn up by the surgeon) and the scar tissue would likely go some way towards regaining the stabilising factor previously provided by the ALL.

I'd also suspect that in the same way its pretty easy to re-sprain an ankle once its been sprained once - that the area would be a bit less stable after surgery (this seems like common sense anyway).

It re-inforces to me the need to wait a long time (at least several months but probably longer) before participating in any risky/rough sort of activity that might cause overextension or rotation, to allow the area to form scar tissue and allow muscles and the other surrounding ligaments (posterior longitudinal ligament, ligamentum flavae etc.) that may have been stretched during surgery to restore their previous elasticity.

But it doesn't sound like there's any particular risk of the neck 'popping apart' at the ADR level from a mild overextension injury, though you'd think it'd be a bit more vulnerable than prior to the surgery because some of the stabilising factors have been lost. (again this is plain commonsense). How much larger this risk would be during a significant extension/rotation type impact would be pretty difficult to answer or study in any quantitative way.

Also still difficult to answer the question about which would be more risky - an ADR or ACDF. You'd think ACDF would be more stable on extension, but would add significant extra load to adjacent discs and structures on a hard flexion injury which could be equally as risky.

Anyway, thanks for all the replies to this thread, I've found it a helpful discussion so far (even if I'm still confused ).