[LBP]

it almost sounds like you're saying your employer is self insured and they use a third party administrator.

If that's true, you'll want to figure out who makes that decision at your company and start preparing to make your case. Some people have been successful getting coverage BECAUSE their company was self insured and they had certain things going for them as an employee like:

how high up in the company you are, how long you've worked for the company, the kind of work (how valuable and indispensible) you are for your company.

Also if you make the dollars case for them...compare prices, possible furture surgeries with fusion compared to ADR etc as well as pointing out how much quicker the recovery is supposed to be for ADR, and thus returning to work sooner than if you had fusion.
You'll probably want to do some research for specific data and articles to prepare for this kind of discussion. You'll want to present a clear and convincing argument for ADR.

You can seach people here for there success with self insurance situations. I know one who doesn't post anymore is ESL but there's someone recent who I cant recall their name.