By Associate Professor Greg Cunningham, Dr Paul Taylor, Spine Surgeons, and Dr Gareth Dobson, Spine Fellow
The recent Australian burden of health review revealed ‘back pain and problems’ to be the second most recorded cause of disease burden. Cervical degenerative disease (CDD) has been shown to affect over 50% of those aged 40 and over.
Patients with CDD generally present with either neck pain, radiculopathy, myelopathy or a combination. While many patients improve with conservative measures alone, those with unremitting symptoms, progressive neurology or significant neurological compromise often require surgical intervention.
Historically anterior cervical discectomy and fusion (ACDF) has been the go-to gold standard surgical option. Accessing the cervical spine from the front of the neck allows excision of the target cervical disc and underlying osteophytes, thereby relieving the identified neural compression.
An iliac crest bone, polyether ether ketone (PEEK) or 3D-printed titanium cage can be placed into the cleared disc space, aiming to achieve fusions between the two adjacent vertebrae. Despite the fact ACDF has been demonstrated to be efficacious, development of compressive adjacent level degenerative disease has been observed in up to 10% of individuals five years post-operatively and up to 40% at 10 years.
Cervical disc replacement
The concept of a cervical disc replacement (CDR) was pioneered by Dr Ulf Fernstrom in the 1960’s. This ultimately aimed to retain mobility of the cervical spine, reduce the stress on neighbouring cervical levels, and subsequently reduce the progression of neighbouring level disease.
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Unfortunately, early attempts were plagued with both surgical and device-related complications, including dysphagia, implant migration and cervical instability. Marked improvements in arthroplasty devices have been made with several devices on the market.
Not everyone with CDD is a candidate for cervical disc arthroplasty, with several contraindications frequently cited. These include patients with cervical instability, severe facet disease/spondylosis or osteoporosis. Indications for cervical disc replacement generally include adults with radiculopathy or myelopathy resulting from either one- or two-level spondylosis – between C3-C7 – who have failed at least six weeks of conservative management.
Reduced reoperation
Long-term data is now available for disc replacement, with the Byran disc device offering 20-year data from a RCT against ACDF. There is a 10% reoperation rate compared to the 41% reoperation rate of ACDF.
Further randomised control trials, with 2–10-year follow-up, comparing cervical disc replacement to ACDF support these findings.
The reduced reoperation rate after CDR is due to its potential to reduce the incidence of adjacent segment disease (ASD). Meta analyses assessing the long-term CDR outcomes have demonstrated significantly lower rates of symptomatic ASD and subsequent re-operations at adjacent levels compared to ACDF.
Rates of reoperation at the operated level provide another comparison between CDR and ACDF. In this case, ACDF typically has a lower rate of revision likely due to the static nature of a fusion.
A mobile disc replacement, like any joint replacement, can lead to issues such as implant wear, loosening or subsidence and continued abnormal bone growth around the prosthesis. Each of these may potentially require revision surgery.
While higher revision rates have been observed at the index level, long-term data still suggests higher total rates of second cervical procedures in ACDF patients.
Retaining mobility
The major aim of disc replacements is to mimic normal movements of the native disc, retaining mobility at the operated segment.
Post-operative studies show CDR effectively maintains range of movement at the operated level, with longer term studies confirming that the preserved cervical kinematics are maintained in a high percentage of patients.
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CDR as a result has also been demonstrated to be as effective, if not more so, at achieving improvements in recognised outcomes scores, such as the Neck Disability Index (NDI), visual analog scale (VAS) for neck and arm pain, with CDR patients experiencing sustained improvements typically superior to those undergoing ACDF at five-10-year follow up.
Patient satisfaction and quality of life measures also tend to favour CDR in these mid- to long-term assessments.
Patient satisfaction
Cervical disc replacement appears to have cemented a place in the management of cervical degenerative disease, generally performing best in younger, active individuals with one- or-two-level disease who have minimal pre-operative degeneration.
Over recent years a number of groups have reported on its potential use in multilevel disease. A seven-year review of patients with three or four level cervical disc arthroplasty observed high rates of patient satisfaction and retained long-term improvements in outcome scores, suggesting this may be a future avenue.
Additionally, a recent increase in reporting of the use of hybrid constructs in which multilevel cervical degenerating is managed with a combination of disc arthroplasty and fusion has occurred, with future randomised control trials planned.
Key messages
- CDR offers outcomes at least equivalent to ACDF, with advantages in motion preservation, reduced ASD, and fewer adjacent-level surgeries.
- Both procedures effectively alleviate symptoms, but CDR may provide more function for some candidates.
Continued surveillance beyond the current follow-up, and assessment of additional indications, will enable further assessment of the lifespan and utility of CDR implants.
Author competing interests – nil
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