BC/BS Denial-"Experimental" Procedure

Recently, my BF was denied by BC/BS for a C5 disk replacement citing that it was an experimental procedure.  He is having severe right arm numbness, pain and it prevents him from doing meaningful work/ activities.  We have 3 physicians that state it is medically necessary.  The surgery has been FDA approved for several years but the insurance company is still considering this experimental yet they will pay for a fusion makes no sense when there is a significant likelihood of additional disk degeneration in the future.

We are trying to appeal this but as such, BC/BS seems to have all the power and control.  Are there any suggestions to successfully waging an appeal?