This is a plain English summary of an original research article
As in the back, discs in the neck can degenerate and cause pain and nerve damage from pressure by the disc, in this case for cervical nerves. In severe cases, where nerves are affected surgery is performed to relieve pain and numbness. This systematic review of trials found that replacing a damaged disc with an artificial substitute in the neck was better than removing the damaged disc and fusing the vertebrae either side. Compared with fusion, disc replacement improved neck function, reduced pain, and led to fewer further operations for up to five years after surgery.
These findings are in line with 2010 NICE guidance on cervical disc replacement. 2015 NHS England commissioning guidance says fusion surgery is less expensive than disc replacement, but looks less cost effective two to three years after surgery. There is little evidence on effectiveness or UK-based cost effectiveness more than five years after surgery, so we don’t know which is best over the long-term.
Why was this study needed?
Damage to a disc between the bones of the neck can be caused by injury, disease or infection. Wear and tear can worsen the damage, causing the disc to bulge and press on nearby nerves. This can cause symptoms like neck and arm pain, and arm tingling and numbness. Surgery is an option for those at risk of nerve damage or whose symptoms do not improve with time.
The usual surgical treatment - anterior cervical decompression and fusion - removes the damaged disc and fuses the bones around it using a bone graft to fill the gap. This can relieve pain but restricts neck movement and risks further degeneration of adjacent discs, which might need further surgery.
Replacing a damaged disc with an artificial joint - cervical total disc replacement - is a relatively new operation that preserves neck movement. In 2013/14 the NHS carried out 10 times as many fusion operations (6,000) as disc replacements (600).
A 2012 Cochrane systematic found that the two operations had similar outcomes two years after surgery. This review aimed to extend and update the evidence-base using studies with follow-up longer than two years.
What did this study do?
This systematic review searched for randomised controlled trials comparing fusion surgery with disc replacement surgery in adults with symptomatic cervical disc disease. Only trials reporting effectiveness and safety outcomes more than two years after surgery were included.
The review included 19 trials involving 4,516 adults. Results were combined using meta-analysis. Eighteen trials had a low risk of bias; one had a high risk of bias. This, and the fact the review followed best practice guidelines on systematic review methods, means the results can be considered reliable.
What did it find?
- The operation was deemed successful if it significantly improved disability and relieved nerve symptoms and avoided side-effects and further surgery. 78% of replacements were successful overall compared to 69% of fusion operations. (OR, 0.59; 95% CI: 0.48 to 0.74).
- Disc replacement surgery improved functional recovery at four to five years after surgery, though different outcome measures were used and only two trials were included in the meta-analysis (standard mean difference, -0.31; 95% CI -0.47 to -0.15).
- By two to three years after surgery, adverse events were more common after fusion surgery than disc replacement (OR 0.58, 95% CI 0.43 to 0.80). These adverse events included problems with the new joint and difficulty swallowing.
- At five year follow up, fewer people having disc replacement surgery needed additional surgery at the original operation site. However, the same number of people in both groups needed further surgery to repair adjacent neck vertebrae.
What does current guidance say on this issue?
2010 NICE guidance on neck disc replacement says disc replacement is as least as effective as fusion in the short-term, and may result in reduced need for further surgery in the long-term. Disc replacement in the neck should only be carried out by specialist centres. 2015 NHS England commissioning guidance confirms these findings and advice. It notes the lack of UK long-term cost effectiveness research comparing these procedures, and lack of research about the safety of artificial discs after many years in place. This commissioning guidance is due to be updated in 2017, while no date is given for the NICE guidance update.
What are the implications?
This systematic review is consistent with 2010 NICE guidance on cervical disc replacement and 2015 NHS England commissioning guidance for this procedure. The review found disc replacement was more effective than fusion surgery for neck function, pain, mobility and adverse events two to three years after surgery, and reduced need for additional surgery at the same site up to five years after surgery. A lack of evidence on outcomes past five years limits what can be said about longer-term effectiveness, including development of disease in adjacent spine areas, long-term safety of artificial discs and need for further surgery. This review also didn’t consider the cost effectiveness of the operations and it didn’t compare surgery with not having an operation, such as just having rehabilitation.
Zhang Y, Liang C, Tao Y, et al. Cervical Total Disc Replacement is Superior to Anterior Cervical Decompression and Fusion: A Meta-Analysis of Prospective Randomized Controlled Trials. PloS one. 2015;10(3):e0117826.
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