Everything points to improvement in final outcomes with ADRs. There is less soft tissue damage for disc replacement now. The time it takes to do the surgery is less with less blood loss. Hospital stays are longer if there is more than one level operated on.
Studies are just beginning to compare single-level replacement with multiple level implants. The short-term (up to two years) and mid-term results (two to five years) are very positive. The first FDA pilot study published results on the use of multi-level cervical spine ADRs. They compared outcomes against single-level implants.
The patients with the multi-level ADRs had better motion and function. They had less pain and less disability. This was when results were compared to a similar group of patients who only had a single level replaced.
It will still be awhile before multiple level operations are done routinely. For now, the safety and improvements with single level implants are consistent and encouraging.