The bones (vertebral bodies) that make up the spinal column have discs located between them. The spinal column is separated into four regions- the cervical (C), thoracic (T), lumbar (L), and sacral (S) spine. The discs are named individually by the level of the vertebra above and below them (eg. the lowest disc is called the L5-S1 disc).
In a healthy spine, the discs and the facet joints bend to allow motion between the bones of the spine. The discs are made up of a tough outer wall (the annulus fibrosis) and a soft inner region (the nucleus pulposis). Like a knee joint, the spinal facet joints have a smooth cartilage surface that makes movement comfortable.
These discs and facet joints allow the vertebrae to flex (bend down) and extend (bend backward). The discs and joints also allow a certain amount of rotation.
Bulging & Herniated Discs
A disc bulge or a disc herniation (also called a protrusion or extrusion) is an injury to the disc. In some cases, the tough outer wall of the disc bulges out — a disc bulge. If there is a bleb that forms, this is called a disc protrusion. In other cases, the soft inner material from the disc pushes right through the tough wall, spitting out a ‘free fragment’ — a disc protrusion or extrusion.
Disc bulges, herniations, protrusions, and extrusions typically cause neck or back pain, oftentimes with associated radiating pain, weakness, and/or numbness to the arms or legs. This pain can be debilitating.
Some disc herniations heal on their own over a matter of months. Others may not heal on their own, which can lead to persistent pain.
There are a variety of surgical options for patients with pain from unhealed discs. These options broadly fall into three categories- decompression surgeries, fusion surgeries, and disc replacement surgeries.
Lumbar disc herniations can often be debulked (“smoothed down”) through a microdiscectomy or laminectomy. If this fails to provide relief, a fusion surgery or a disc replacement might be considered. On some occasions, a fusion or disc replacement might be recommended if a patient is not a good candidate for a decompression surgery.
- A lumbar disc replacement surgery is done through an anterior approach (through your belly). While this is generally quite safe, it is a very technically challenging procedure, with a higher risk of bleeding than most minimally invasive or traditional spine fusion procedures. Generally, you will have two surgeons during the case- a vascular surgeon in your surgery to protect the abdomen and the blood vessels to your legs so that your spine surgeon can take out the old disc and place the disc replacement safely. Relatively few surgeons are familiar and comfortable with lumbar disc replacement.
- Cervical disc herniations are most often managed with cervical fusion or disc replacement, although occasionally a decompressive procedure might also be possible- a cervical foraminotomy. Cervical disc replacement is less invasive and more commonly done than is lumbar disc replacement. Unlike lumbar disc replacement, cervical disc replacement is also commonly done on more than one level.
There is good evidence that both spinal fusion and disc replacement are both safe and effective, whether done in the cervical spine (neck) or the lumbar spine (lower back). That said, there are important differences between these techniques which a surgeon will carefully consider when recommending a surgical solution for a disc problem.
On a basic level, spinal fusion is a procedure done to stop the disc and joints from moving; this restricts motion at a level or levels of the spine. Disc replacement is done in order to preserve motion. Spinal fusion remains the ‘standard of care’ as it is the older, more completely studied solution.
Disc replacements have been done since the 1950s, but the earliest devices used often failed. After nearly 70 years of innovation, the newest devices are both safer and more effective. That said, health insurance companies are typically skeptical of any new technology. That is changing quickly as more research documents that artificial disc can provide great advantages over spinal fusion. If you are considering a disc replacement, it is quite important to see a spine surgeon who is familiar with the disc replacement literature and with your insurance’s policy on disc replacement, as obtaining authorization can be difficult.
Both fusion and disc replacement have been shown to provide good pain relief, with studies showing improvement up to and beyond 10 years out from surgery. Many studies show that two-level cervical (neck) disc replacements seem to do better at 10 years than do two-level fusions.
Beyond the 10 year point, it is felt that both cervical and lumbar disc replacements would place less stress on the other, healthy discs; many surgeons believe this will lower the risk of a second herniation and the need for other spine surgeries later on in life. Unlike knee or hip joint replacements, there does not appear to be a “lifespan” after which a disc replacement wears out, although this is still being studied.
While the FDA has approved and allows disc herniations to be done on both the cervical and lumbar spine, there are specific criteria in which a disc replacement may or may not be an option for a patient. Lumbar disc replacements are more technically challenging than cervical disc replacements. A careful discussion with a spine surgeon that is familiar with your case and is comfortable with both techniques is recommended prior to deciding on a treatment for your disc herniation.