Link/study from UHC dated Oct 2011 that explains their position,
"Cervical artificial total disc replacement is proven for the treatment of single level degenerative disc disease in skeletally mature patients when used with FDA approved implants"
"Cervical artificial total disc replacement is unproven for the treatment of multiple level degenerative disc disease in skeletally mature patients."
"Lumbar artificial total disc replacement is unproven for the treatment of single or multiple level degenerative disc disease in skeletally mature patients."
https://www.unitedhealthcareonline.c..._the_Spine.pdf