Kaiser Family Foundation newsletter covers the topic of insurance denials from time to time.
You, as the "client" are entitled to the entire file at the insurance company to include who made the denial(s) decision, their credentials (e.g. RN, MD, and so on) AND the National Provider Id number (NPI) of that provider making that call. You can ask for (demand) their specialty and ask if they are board certified as a surgeon --orthopedic or neurosurgeon. Usually first round of denials are by low level non-professional employees from a predetermined script. Appeals go to someone with some medical knowledge but that could be a retired urologist, or GP or internal med doc...or an RN who is not well versed in your spinal conditions nor current on treatment modalities. It's its own kind of corporate maze to work through. One has to be diligent about it all and have a second who can support you through this if possible because pain, pain meds etc can also slow you down while you are stuck doing all your slef-advocacy.