Wouldn't that depend upon what the insurance company's definition of "medically unnecessary", and why it took two years for them to come to that conclusion?.... if I was your patient, not only would I not pay, but I would most likely sue if I was asked to pay bills for treatments found "medically unnecessary".
Example: Patient presents with a history of GI bleed, is complaining of burning/stomach pain after eating, and a positive at home test for blood in the stool. Doctor orders a very basic blood count (CBC) ....totally logical, right? Insurance company comes back a year later (after paying the claim), stating the CBC was "medically unnecessary". Why?...because the CBC results came back within normal limits. Isn't hindsight wonderful? Ridiculous.
Obviously, OP did his/her homework by submitting treatment plans which supported the initial decision by UHC to authorize treatments. They then continued to pay for 22 visits. Now, 2 year down the road, they change their minds and demand their payment back? IMHO, it's disgusting.

