For the study, the researchers analyzed data on lower back (lumbar) surgery among Medicare recipients aged 65 and older nationwide, between 1992 and 2003, and found a dramatic increase in spine surgery during this time period.
The researchers found that surgery rates in 2002-2003 were almost 8 times higher than in 1992 in some areas of the US, and in 2003 Medicare spent over $1 billion on spine surgery.
Although the number of people with back problems does not differ that much in different parts of the country, high surgery rates were found in places like Casper, Wyoming, and Mason City, Iowa, and the lowest rate areas included Honolulu, the Bronx, New York, East Long Island, New York, and South Bend, Indiana.
According to the study, nearly five out of every 1,000 Medicare patients in some parts of the country underwent spinal surgery, compared to as low as 0.2 per every 1,000 in Bangor, Maine and 0.3 in Terre Haute, Indiana.
Johnson & Johnson's DePuy Spine Unit began marketing the Charite artificial spinal disc in the US in 2004. It was supposed to reduce the need for spinal fusion and other back surgeries. However, the Charite has now been linked to life threatening side effects leaving many surgeons reluctant to use the device.
Some surgeons say the artificial spine discs currently on the market are based on flawed science. Researchers at the University of California at Irvine say they believe the device makers have made a crucial mistake in designing the discs.
According to the doctors, the error stems from a lack of understanding of spinal biomechanics. A crucial miscalculation, they say, explains why the artificial discs have experienced repeated failures with serious consequences for many patients.
"They've based their center of rotation on a disc space that is in front of the spinal canal," says Dr Charles Rosen, a Cal-Irvine spine surgeon who has been critical of the Charite disc, in an interview with The Street.com on October 23, 2006.
"Our model," he explains, "which takes into account the complications that have occurred with these discs, suggests that the center of rotation is in the back of the spinal canal instead."
"So their design is wrong, period," he told Street.
According to Dr Rosen, the artificial discs disrupt the spine's normal function by creating an "artificial center of rotation" in a disc space that lies in front of the spinal canal, rather than behind it, which compromises the body in the process.
"You have a center of rotation that's normally there, and they falsely impose another," Dr Rosen told Street.
"You can't have two because they will neutralize each other," he explains. "Something has to give."
"To give, either the back part of the device breaks or the front part dislocates," he notes. "Then you have a failure."
Dr Rosen says he has seen the problem in the Charite and also in ProDiscs, a recently FDA approved disc now being marketed in the US by Swiss device maker Synthes.
According to Dr Rosen, many of the discs that do work, do so only after "auto-fusing" bones together, simulating fusion surgery and ruining the prospect of natural motion that makes the artificial discs so appealing in the first place, he told Street.
Indeed, in announcing the FDA approval of the Charite disc in a press release on October 26, 2004, the company did tout the Charite as "a high-tech device made of two metallic endplates and a movable high-density plastic center that, once implanted, is designed to help align the spine and preserve its ability to move."
"Spinal discs," the press release said, "maintain the position of the spine and allow for the flexibility to bend and twist."
"Lumbar spinal fusion surgery," J&J said, "is often effective in reducing pain, but limits range of motion and may transfer extra stress to discs above and below the fusion site."
"In clinical trials comparing artificial disc replacement to spinal fusion surgery," the company said, "patients maintained flexibility, experienced improvements in pain and function, left the hospital sooner and were more satisfied with the procedure."
It would certainly seem that Dr Rosen is correct when he says that if auto-fusing bones together is also needed in order for the Charite implant to be successful that it would negate the reason that people would be willing to pay for the expensive disc replacement surgery instead of the much cheaper spinal fusion surgery.
Critics point out that the cost of the disc and accompanying surgery can run as high as $50,000, while the cost of lumbar fusions surgery, on average, is less than half that amount at about $23,000.
If informed of the facts, people probably would not opt to have disc replacement especially when according to the J&J press release, "Complication rates for both groups of patients were similar."
Once implanted, the artificial discs are expected to last a life-time but experts say an analysis of several discs that were removed from patients showed wear similar to that found in artificial hips and knees that typically last up to 10 years. While this might be acceptable in older patients, they say, it is not acceptable for younger patients who would have to undergo life-threatening surgery to remove the disc once it wears out.
Since the Charite was approved for use in the US, more than 5,000 patients have received the implant, according to DePuy Spine's vice president, Bill Christianson, in USA Today on July 25, 2006.
However, as of the same month, July 2006, the FDA had received more than 130 reports of serious adverse events associated with the Chirate.
In addition, the Houston law firm of Pulaski and Middleman, leads a group of firms that represent over 350 patients who have been injured by the Charite. And according the Street.com on June 5, 2006, a Chicago law firm has more than 200 clients who have suffered complications from the disc and are seeking reparations.
Some experts are predicting that in the not too distant future the situation will get much worse and there will be a surge of patients who will experience complications which will be extremely problematic because the disc removal surgery can be more dangerous than the original implant procedure.
According to the Texas Back Institute's Center for Spine Arthroplasty, in the standard artificial disc implantation procedure, two surgeons work together:
"A general surgeon approaches the spine through an incision in the abdomen and carefully moves blood vessels and internal organs out of the way to provide access to the spine. A spine surgeon then removes the damaged disc to create a space between two vertebrae for the implantation of the artificial disc, which is done using fluoroscopic guidance. Generally, the procedure takes about 60 to 90 minutes for a single level."
Although the disc implant surgery described above sounds simple enough, if problems develop, experts say, corrective procedures are far more complicated, if they can be done at all. According to Santos et al:
"Revisions surgery for a failed disc arthroplasty is life threatening. Dealing with the scarring around the great vessels is the main challenge.
"Indeed, the location of vital vascular structures may make it altogether impossible to perform such anterior abdominal exposures."
Experts say that other postoperative difficulties such as infection, persistent pain, instability, and osteolysis can also occur.
Many critics fault the FDA for approving the Charite in the first place. The original 2-year study submitted to the FDA in support of the application for approval, showed only that the disc worked no worse than one specific outdated type of spinal fusion surgery.
But even when compared to a procedure hardly used anymore, the study found that only 57% of Charite patients achieved "overall clinical success," compared with 47% in the spinal fusion patients, and more than 3 out of every 5 Charite patients, reported as successes, were still taking narcotic painkillers 2 years after the surgery, compared to 4 of 5 patients in the control group.
In addition, the study found Charite patients suffered more severe or life-threatening adverse events than patients in the spinal fusion group by a difference of 15% and 9%, according to an FDA review.
Amidst allegations that the expensive Charite disc replacement was being overly performed on Medicare patients with poor results, the government recently took measures to put a stop to that situation. On June 1, 2006, the Centers for Medicare & Medicaid Services finalized its national noncoverage decision regarding the Charite disc, banning reimbursement for the device among recipients over the age of 60.
"The Centers for Medicare & Medicaid Services has found that lumbar artificial disc replacement ... with the Charite lumbar artificial disc is not reasonable and necessary for the Medicare population over sixty years of age," the CMS decision said.
And just as expected, many private insurance companies have followed suit.
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