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.
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.
The future of artificial disk replacement technology will likely include significant advancements in the design of implants, tools for diagnosis of the source of pain, and other approaches to regenerating the disk to normal function.
The American Academy of Orthopaedic Surgeons
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