Allan... I don't think there is any reasonable way to snap the keel off. The plate is one piece, cobalt chome.... not breaking. Various lateral approaches would be for removal of prosthesis but not to consider reimplantation of the current crop of devices... must be done from the front. As I write this, I do know doctors who are developing implantation techniques that allow lateral approach for total disc replacement. Also, there are keeled devices that have adjustable or selectable keel angles to allow oblique or lateral implantation once the approach has been developed. Imagine the geometry of implanting a keeled device from an angle. The keel cut must be perfect and there is only one place where midline placement intersects the a/p (anterior/posterior) placement of the device. That is where it will be without regard to endplate shape, tension, etc... no latittude in adjusting placement there. I usually see fine-tuning placement based on unique confuguration that is achieved after initial placement.
I can't really speculate about what might happen in revising ProDisc at L4-5. I know surgeons who do it without difficulty. I know surgeons who would not even try that technique and will elect to do a procedure that they perceive to be less risk in spite of more damage done. Also, once you get into revision surgery, each case is unique. I do beleive that we must go into our initial ADR surgeries expecting success and revisions issues, while important, are not paramount. I would not take a fusion instead of ADR because revising ADR may be difficult or risky. Revising failed fusion is risky too, for other reasons, but once you are having a revision, your life is on the line no matter what is being done. There are overriding concerns about the different disc designs in particular configurations that outweigh other issues. Our problem in trying to be informed patients is that we get so much conflicting information from very convincing sources. It is tough for us to know how much weight to assign to the different issues.
Mark
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