Millions of Americans suffer with chronic lower back pain caused by ruptured, herniated or deteriorating discs. Although painkillers and exercise help most people, about 200,000 a year must resort to spinal fusion, a complicated procedure with a lengthy recovery.
Even then, some spines become stiff, causing the patient to lose mobility. But soon people with severe pain may have an alternative: an artificial disc.
First devised in 1984 by two German orthopedic surgeons, the prosthesis, known as the SB Charite Artificial Disc, has been available in Canada, Europe, Asia and Latin America for more than a decade and implanted in more than 5,000 people worldwide.
Tests of 364 patients in the U.S. were completed in December 2001. Before granting approval for sale here, however, the Food and Drug Administration requires that the patients be followed for two years to see if the devices hold up and if there are any complications. Once those data are compiled, the prosthesis could be available here in 2004.
"This is a significant advance," says Dr. John J. Regan, an orthopedic surgeon at Cedars-Sinai Medical Center who has implanted the experimental device in 45 patients. "Recovery is quick, and it restores motion to the part of the spine that would otherwise be fused."
The disc consists of a polyethylene core that slides between two metal plates attached to the vertebrae of the spine. The core functions on a ball-and-socket principle that mimics the action of healthy discs, permitting motion and flexibility; the plates keep the spine stable. Because the prosthesis is made of the same materials used for more than 30 years in other orthopedic devices, such as hip and knee replacements, infection is unlikely.
Insertion of the device is performed through a small incision in the abdomen. Surgeons push the stomach and intestines aside to expose the spine, remove the damaged disc and insert the implant. Rehabilitation begins after hospital discharge, which is usually two days after the procedure. Patients are urged to move the joint normally as soon as possible. Still, spinal fusions won't become obsolete any time soon. People with more than one damaged disc or who suffer from osteoporosis aren't good candidates for disc implants. But for otherwise healthy people, artificial discs are "a real breakthrough," says Dr. Scott Blumenthal, an orthopedic surgeon who tested the device at the Texas Back Institute in Plano, "because they can restore normal functioning."
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The body's spinal discs are gel-like cushions found between each of the 24 bones in the spine, giving the back stability and flexibility. But discs can deteriorate due to accidents, muscle strain or the normal wear and tear of aging. Such damage can cause the cushion to deflate, bulge or leak, which can trigger intense pain, especially if nerves are pinched.
Physical therapy and exercise can strengthen muscles, which give the discs more support, or ease the muscle tightness that can cause a disc to protrude and damage nearby nerves (a condition known as a herniated disc). Painkillers and cortisone injections, which shrink swollen discs and ease inflammation, can help.
Sometimes, however, surgery is the only option. In one procedure, discectomy, part of the disc is removed to relieve pressure on nerves. A more radical procedure is a spinal fusion, in which the disc is replaced with a bone graft from the hip.