Regarding this:
"...there is in fact some retrolisthesis there, but it's really mild, and that he would still prefer to do the ADR. In fact, he said if it was his own neck, and his films looked like mine, he would put an ADR in his own spine. He was definitely confident..."
You may want to get a more precise assessment on this. Every doc and disc mfr. has slightly different contraindications regarding retrolisthesis, so be careful. The flexion-extension images are usually helpful to the patient and doctor on this. Make sense?
See this link, table 1 and references:
http://www.ncbi.nlm.nih.gov/pmc/arti...25514/#CIT0007
And for review:
https://en.wikipedia.org/wiki/Retrolisthesis