You most likely have significant degenerative changes between C5-6 and C6-7 compressing the cord and/or nerve roots. The surgery you describe is a reasonable alternative to the standard C5-7 ACDF. You are having an ACDF at C6-7 (see website for description of that surgery) and an artificial disc at C5-6 (again- see website). The question then boils down to how does the artificial disc differ from the ACDF?
The artificial disc replacement (ADR) was designed to allow motion of the surgical segment. The motion of the ADR is not normal but close to normal. The ADR will not absorb shock like the normal human disc will. There are two problems with the ADR. One is that it will wear out eventually and need to be replaced. This obviously requires another surgery. The second is that if there is a significant component of neck pain complaints, this ADR may not relieve the neck pain.
Even with regard to the above two problems, I think this disc replacement is a good surgery and is reasonable in the right individual.
Dr. Corenman