[ans]

Thanks for your help.

Also Mark, I'd like to be in touch with spondy pts. who've had ProDisc. I do not know the cut-off margin e.g. 4mm displacement and Regan and Lauryssen seem unconcerned about it. Yet, the literature shows some concern re: fusion.

Hmm, so if the keel is nicely attached to the bone, I wonder to what degree instability/torsion can break it from the bone. This sounds like a question worth pursuing - maybe Drs. Delamarter, Dr. B., etc.

Best ~ Allan