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Spinal Disc Replacement
Low back pain is a significant cause of disability in the
U.S. and worldwide. It is estimated that 70% to 80% of
people will experience low back pain at some point in their
lives.
Artificial disk replacement is a newer surgical procedure
for relieving low back pain. Similar to hip or knee joint
replacements, a disk replacement substitutes a mechanical
device for an intervertebral disk in the spine. The device
is meant to restore motion to the spine by replacing the
worn, degenerated disk.
This technology has been available in Europe for over a
decade. Artificial disk replacement initially gained FDA
approval for use in the U.S. in 2004. Over the past several
years, numerous other disk replacement designs have been
developed and are currently being tested.
Lumbar fusion surgery remains the "gold standard" for
treating low back pain patients who are not helped by
nonsurgical methods. Although many people with low back pain
find relief with lumbar fusion, the results of the surgery
vary. For example, a patient with spinal stenosis who has a
fusion procedure may have a very different outcome from a
patient who has a fusion to help back pain that is caused by
disk degeneration.
In addition, some patients whose fusion surgeries heal
perfectly still end up with no improvement of their back
pain.
There are many reasons for the failure to improve after
fusion surgery, but some doctors believe it may be due to
the fact that fusion prevents normal motion in the spine.
Artificial disk replacement has emerged as an alternative
treatment option for low back pain.
To determine who is a good candidate for disk
replacement, the surgeon may require a few tests. These may
include magnetic resonance imaging (MRI), discography,
computed tomography (CT or CAT scan), and x-rays. These
tests will also help the surgeon determine the source of the
pain.
Good candidates for disk replacement have the following:
- Back pain thought to be caused mostly from one or
two intervertebral disks in the lumbar spine
- No significant facet joint disease or bony
compression on nerves
- Not excessively overweight
- No prior major surgery in the lumbar spine
- No deformity (scoliosis)
The surgical implantation procedure is performed through
an incision in the abdomen (similar to an anterior lumbar
interbody fusion). With this approach, the organs and blood
vessels must be moved to the side. This allows your surgeon
to access the spine without moving the nerves. Usually, a
vascular surgeon assists the orthopaedic surgeon with
opening and exposing the disk space. Most surgeries take
about 2 to 3 hours.
Disk Design
The disk
replacement device may comprise the nucleus (center) of
the disk while leaving the annulus (outer ring) in
place, although this technology is still in an
investigative stage.
In most cases, total artificial disk replacements
substitute the annulus and nucleus with a mechanical
device that will simulate spinal function.
There are a number of different disk designs. Each is
unique in its own way, but all maintain a similar goal:
to reproduce the size and function of a normal
intervertebral disk.
Some of the disks are made of metal, while others are
a combination metal and plastic, similar to joint
replacements in the knee and hip. Materials used include
medical grade plastic (polyethylene) and medical grade
cobalt chromium or titanium alloy.
Most patients are encouraged to stand and walk by the
first day after surgery. Because bone healing is not
required following an artificial disk implantation, the
typical patient is encouraged to move through the
mid-section. Early motion in the trunk area may translate
into quicker rehabilitation and recovery.
The typical hospital stay is 2 to 4 days, depending upon
pain control and return to function. Basic exercises during
the first several weeks after surgery include routine
walking and stretching while avoiding hyperextension
activities.
Patients can expect improvement of lower back pain and
disability in weeks to months following surgery. The results
from numerous studies, including FDA-regulated trials,
reveal that disk replacement improves, but does not
completely eliminate pain. It is critical that prior to
surgery the patient and the treating surgeon develop
realistic expectations of pain relief.
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