When operating on a patient with a disc prolapse in the neck, the surgeon has three options:
To simply remove the prolapsed disc, with any protruding bone (osteophyte), and leave the residual disc in place. This is referred to as a cervical discectomy and is performed most commonly in the lumbar spine with generally good results. It is simple and tends to leave the joint a little more flexible than it was. Sometimes this can result in the joint becoming too flexible, as after a year or so most cases will show that the bone has grown across the disc space making it stiffer than before. This may then lead to adjacent discs becoming more worn and then prolapsing some years later in up to a quarter of cases. In a small proportion of cases, probably less than 10%, bone formation at the edge of the disc (osteophytes) can compress the emerging nerve roots which can give rise to new symptoms, usually in the arms.
Alternatively the surgeon can choose to fuse the disc space by putting bone graft or a small spacer, a small plastic ring through which bone grows, into the disc space. This is the basis of the anterior cervical discectomy and fusion, which has been the most commonly, performed procedure for a cervical disc prolapse over the years. It has been very successful for the treatment of acute severe arm pain (brachialgia) caused by a disc compression of a cervical nerve root. However, some disadvantages have emerged after surgery aside from the immediate complications. Up to a quarter of patients returned some years later because the adjacent disc level was causing new symptoms; usually another nerve being compressed, causing recurring arm pain.
These recurring problems have lead to new research aimed at keep the disc moving by replacing it with a moving prosthesis, or disc replacement. This is known as cervical arthroplasty. The first of these disc replacements did not produce better results than fusion, but new developments rising from advances in materials and in the treatment of other joint replacements (hips, knees, toes, fingers) have led to a variety of successful cervical disc replacements. They are largely easy to insert after removal of the disc and are monitored by direct vision as well as intra-operative X rays, to gain optimal positioning. Long term outcome (seven year post operation) has now been documented in a number of prospective randomised clinical trials. Overall, the risk of a second operation is around 17% if the disc is fused compared to around 6% using a disc replacement.
Most disc replacements are made from titanium with a plastic ball and socket joint construction. Original disc replacements consisted of titanium on titanium ball and socket structures that have the potential to produce micro fragments of metal that may be disadvantageous, although this is not yet certain. Some are ceramic, which has the advantage of little or no artefact on imaging using magnetic resonance (MR scan). A titanium based implant usually obscures the image on the scan. From the patient’s perspective, the approach and the resulting scar are similar to decompression and fusion (a transverse skin crease neck incision), and the early neck stiffness is much the same. Hospital stay is usually overnight only. Although clinicians will not advise a disc replacement in a patient with significant spinal cord compression, in younger patients particularly this is emerging as the procedure of choice.
Following a disc replacement, care is largely similar to cervical fusion; no collar is required routinely, and physiotherapy is usually commenced at about three weeks after operation. Return to work is usually from three weeks onwards, depending on the nature of work. An ache between the shoulder blades may persist for 5 to 6 weeks, and some patients notice a clicking noise for a few weeks after insertion which then fades. Sports players will probably benefit from a specific neck strengthening programme prior to retiring to sport.