What is the difference between an anterior cervical discectomy/fusion and a cervical disc replacement?

Both procedures are used for treatment of long term neck pain, neurological deficits, and radiculopathy stemming from the degenerative changes of the neck. Anterior cervical discectomy and fusion (ACDF), has been the gold standard for years. It involves a surgical procedure where an incision is made in the front of the neck in order to remove part of a cervical disc which lay between two vertebrae. Once the disc is removed the two vertebrae are fused together. This procedure has a very high clinical success rate for alleviating symptoms but is also associated with some negative long term side-effects including loss of cervical range of motion, increased degenerative changes at segments adjacent to the fusion level and an increased reliance on future need to solid bony fusion. A cervical disc replacement(CDR), procedure is relatively new. It involves the same approach as ACDF with an incision on the front of the neck. The disc is removed, but rather than fusing the two vertebrae, and artificial disc is implanted. This procedure also has a high clinical result in symptomatic relief, but it also helps maintain range of motion and can decrease degeneration at adjacent segments.