NIHR Signal Disc replacement is better than fusion in people needing surgery for neck disc disease
Published on 14 September 2015
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.
Boselie TFM, Willems PC, van Mameren H, et al. Arthroplasty versus fusion in single-level cervical degenerative disc disease. Cochrane Database Syst Rev. 2012; (9):CD009173.
Luo J, Huang S, Gong M et al. Comparison of artificial cervical arthroplasty versus anterior cervical discectomy and fusion for one-level cervical degenerative disc disease: a meta-analysis of randomized controlled trials. Euro J Orthop Surg Traumat. 2014. Published online 18 July. DOI 10.1007/s00590-014-1510-4.
NHS England. Clinical Commissioning Policy: Cervical Disc Replacement for Cervical Radiculomyelopathy. Reference: NHS England D14/P/a. Leeds: NHS England; 2015.
NICE. Prosthetic intervertebral disc replacement in the cervical spine. IPG 341. London: National Institute for Health and Care Excellence; 2010.
Tidy, C. Cervical disc protrusions and lesions [internet]. San Francisco (CA): Patient; updated 2013.
Vernon H, Mior S. The Neck Disability Index: a study of reliability and validity. Journal of Manipulative and Physiological Therapeutics. 1991;14(7):409-15.
Wascher, TM. Anterior Cervical Decompression and Spine Fusion Procedure [internet]. Spine Health; updated 2012.
This study is likely to increase clinical interest and demand for cervical disc replacement in preference to fusions. It is unlikely to directly increase patient demand except for the most well-informed patients. Where there is established cervical disc replacement use the study will likely reinforce the clinical position to use it in preference to fusions. From the commissioner perspective, there are several weaknesses; studies have multiple sources of bias, and heterogeneity, outcomes whilst statistically significant, appear to be of limited or minimal clinical significance. The study does not determine any aspect of cost effectiveness or monetary value.
William Horsley, NHS England North of England Specialised Commissioning Team,
Pharmacy Lead for Specialised Commissioning (North East & Cumbria)
Anterior cervical decompression and fusion involves removing the damaged disc(s) pressing on the nerve (decompression), before fusing adjacent sections of spine vertebra with a bone graft. Metal plates and screws can be used to support and protect the spine at this position.
Cervical total disc replacement involves replacing the damaged disc with an artificial substitute and this gives better preservation of movement. Early types of replacement had significant problems with adverse effects, though the newer artificial discs appear improved.
The Neck Disability Index is a 50 point scale where 50 is the worst pain. The review authors used NDI as a measure of functional recovery. They considered a decrease of 15 points or more a significant improvement in function.