Neck Pain and Cervical Disc Replacement: Is a new disc the solution?

Photo by Sebastian Merkelmann (iStockphoto)

Just like many joints in the body, the joints of your neck (called intervertebral discs) can experience wear and tear. This process isn’t unique to the neck, and can happen anywhere in the spine, most commonly in the neck or back. This type of osteoarthritis is called degenerative disc disease. A number of treatments are available for people with degenerative disc disease and typically starts with non-operative management, which includes non-steroidal anti-inflammatory drugs, physical therapy, and steroid injections.

            Unfortunately the non-operative measures are not always effective and a small percentage of people with degenerative disc disease progress to needing surgery. It’s imperative to note that surgery is reserve only for those with end stage degenerative disc disease that is severe, limiting to daily life, and has not responded to conservative measures. The standard of care in surgical treatment of degenerative disease of the neck has been anterior discectomy and fusion (ACDF). This procedure involves an incision in the front of the neck, removal of the intervertebral disc, and fusion of the two vertebra that are adjacent to the degenerated level.

            ACDF surgery has a long track record of success but has a few downsides. Fusion eliminates the motion at the operated levels. This results in two possible side effects. First, the total motion of the neck is potentially decreased.

If the neck bends or rotates to the same degree as before (for example you look up to the same point, like a cup-board), additional stress is placed on the levels above and below the fusion. This is a likely contributor to the increased rate of adjacent segment degenerative disease. In other words, the discs that are next to a fusion seem to develop osteoarthritis at a faster rate.

            Artificial disc replacements were developed in an attempt to solve this issue. The theory is that if the degenerated disc is replaced with an artificial joint that moves, the adjacent segments will not experience any additional stress and will not degenerate at a faster rate. This has been a difficult theory to prove. Cervical disc replacements (disc replacements in the neck) have been increasing in popularity. A meta-analysis performed in 2012 looked at four randomized controlled trials that compared cervical disc replacement with ACDF surgery. The trial found some very interesting results.

            The study showed that there is no statistically significant difference in pain improvement between cervical disc replacements and ACDF. This is an important finding since ACDF is the surgical gold standard for the treatment of this condition. The trial also looked at neurological status, which was defined is maintenance or improvement of muscle strength/tone and reflexes. A higher percentage of people undergoing cervical disc replacement experienced ‘success’ in the neurological status category compared to the ACDF group.

            The study also looked at implant survivorship. Survivorship, as far as the implant goes, is defined as lack of a revision; meaning that the implant was left in at 2 year follow up and did not require any further surgery. The survivorship for cervical disc replacements were on average longer then for the ACDF group. One of the criticisms of this observation, is that a potential confounder would be created if surgeons were more reluctant to perform revision surgery on patients with a cervical disc replacement. However, it is important to note that this theory of bias towards cervical disc replacement has not been proven and is only a potential limitation.

            This study suggests that at the very least, the results of cervical disc replacement for degenerative disc disease of the neck are comparable to that of ACDF surgery. The study only followed patients for 2 years, and we need more long term data in order to draw any more definite conclusions. There are two key questions that the study does not address. First, while the theory that motivated the design of the disc replacement is that less stress is experienced by adjacent levels and this would therefore lead to less adjacent level disease, this theory has never been proven.

The second question is with regards to cost effectiveness. Disc replacements are more expensive compared to ACDF, however if patients leave the hospital sooner or require less interventions after receiving a cervical disc replacement, then the costs may be off-set. Both of these questions are active areas of research. 

Continue Reading