Hi Phillyjoe!
The way it was explained to me by Dr. Bertagnoli when I consulted with him is that grade 1 spondylolithesis can be corrected with ADR, but only using a semi-constrained prosthetic.
The reasoning is that if it is beyond grade 1, there is most likely a pars defect occurring or some other factor that would not be corrected by the prosthetic.
In my case, I think the impact trauma on my lower-back when I was younger, resulted in a simultaneous disc herniation and retrolisthesis. Luckily, there was no bone damage.
My options as presented by Bertagnoli were the Prodisc and the Activ-L. I would not be a candidate for unconstrained devices such as the M6. I also went on to research the Activ-L and found information on their website stating exactly as Dr. B had said: applicable on grade 1 spondylolithesis.
When I consulted with another doctor in the US, he thought the same as you, having only dealt with the charité years ago; that the spondy was an automatic disqualifier. I had him pull up the Activ-L website and showed him right there during our consult the statement from Aesculap.
Needless to say, I did not go back to that doctor. He had never heard of the Activ-L before our meeting and his staff lied to me when I made the appointment with him.
They told me he was performing ADR surgeries when in fact he had stopped. He had been performing them years before when the charité disc was all the rage and had stopped when news came out about the negative results from doctors mucking up the surgeries with bad placement and poor patient selection.
He was one of three doctors I met with in the US where their offices had misled, or some would say lied, to get me in for the visit. Beware people! Don't get roped into a spinal fusion because your doctor is not aware of modern technology and the latest medical procedures!!
Back on topic, I ended up meeting with Dr. Garcia who explained that my grade 1 retrolisthesis would be a piece of cake. He performed the surgery and my spine is now back in perfect alignment after being malaligned for 17 years.
On a funny note, I used to have a bubble-butt because my L5-S1 retrolisthesis caused my pelvis to slip and roll posteriorly about 15-20 degrees. Now that it's corrected, my wife commented that while I still have a nice butt, it's not as big as it used to be
