Cervical Artificial Discs: Valuable New Technology or Fashion?

September 12, 2007
by: Sylvia Marten

Spine surgery, like many other areas of medicine that are experiencing rapid technological growth, is often subject to fashion trends. At this period in time, the fashion is tilted towards motion preservation technology – both in the lumbar spine (low back) and cervical spine (neck). The first artificial disc was approved for the lumbar spine in November of 2004 (Charite, Depuy Spine Inc.) to much fanfare, but for a variety of reasons it has largely not lived up to its expected dominance in the spine industry.

In this author’s opinion, cervical artificial disc replacement should enjoy better overall acceptance and success than lumbar artificial disc replacement by insurance companies, physicians and patients for several reasons:

Preserving motion in the neck will work, because motion is not causing the pain

By its very nature, treating a cervical disc herniation with a motion preservation device (cervical artificial disc) is very different than treating chronic low back pain with a motion device. This is because motion is not the cause of pain for neck surgery, so using artificial disc replacement to preserve the motion (instead of fusion, which limits motion) is practical.

Neck surgery is done to relieve pressure on the nerve root. After removing the cervical disc something needs to replace the disc space or it will collapse (kyphosis). Traditionally, what has been left in the disc space is a bone graft to create a fusion and prevent disc space collapse. However, the motion in the disc space is usually not in and of itself a pain generator, and therefore preserving the motion in this space with a cervical artificial disc is reasonable.

Chronic low back pain because of a painful disc is entirely different from neck surgery. With low back pain, the disc itself may be the pain generator, or something else with the motion at the disc space may be generating the pain. Spine fusions for chronic low back pain work by limiting the motion at the painful level; but preserving the motion in this area by using a lumbar artificial disc may preserve the source of the pain.

Neck surgery to relieve arm pain is a more reliable procedure

When neck surgery is done to relieve arm pain (or back surgery is done to relieve leg pain, or sciatica) due to a pinched nerve the surgery is very reliable. However, neck surgery for either chronic neck pain (vs. arm pain), or low back surgery for chronic back pain (vs. leg pain) is not nearly as reliable. Artificial disc replacement surgery in the neck is indicated for arm pain, whereas the artificial disc replacement in the lumbar spine is not for leg pain (herniated discs). Lumbar artificial disc replacement is designed to treat chronic low back pain due to a painful disc (degenerative disc disease). Lumbar disc herniations resulting in leg pain, if they are treated surgically, are treated with a microdiscectomy, not a fusion or artificial disc.

Indications for cervical artificial disc surgery are more clear-cut

Besides being a more reliable surgery than lumbar artificial disc replacement, cervical artificial disc replacement will also have the advantage in that a new disease entity will not need to be considered. In lumbar artificial disc replacement the disease entity it was intended to treat - lumbar artificial disc disease - is not clearly defined and there is still quite a bit of controversy concerning proper surgical indications for degenerative disc disease, whereas cervical disc herniation resulting in arm pain (radiculopathy) is very well defined and the indications are not at all controversial. For this reason, insurance companies will not be as reluctant to cover any added expense for a new procedure.

When the Food and Drug Administration approved the first lumbar artificial disc many felt that insurance companies would automatically cover the procedure. This did not happen and many have still not approved it as an alternative to fusion surgery. This was unprecedented in medicine as approval usually meant coverage. With the new realities of cost containment in medicine, new technologies with not only have to be proven safe and efficacious, they will also have to be cost conscious.