The Charite artificial disc was first approved for use in the US in October 2004, although it had been used in the European market since 1987. The device was approved to relieve pain by replacing the damaged disc with the Chirate disc, as an alternative to the surgical procedure known as lumbar spinal fusion surgery.
The disc was developed with the premise that segmental mobility will improve outcomes, as has been the case for artificial hip and knee replacements. The current Charite disc is the third modification of a device first developed in 1982 by Buttener-Janz and Schellnack at the Charite Clinic in the former East Germany.
DePuy Spine, a division of Johnson & Johnson, acquired the Link Spine Group in 2003, and gained exclusive worldwide rights to the Charite disc. Since the disc was approved, more than 5,000 people have received the implant in the US, according to DePuy Spine's Bill Christianson, vice president of regulatory affairs, in USA Today on July 25, 2006.
At present, experts claim, the best candidates for disc replacement are adults who have disc degeneration in only one disc in the lumbar spine, either the disc between the fourth and fifth lumbar vertebrae or the disc between the fifth lumbar vertebra and the sacrum.
Under FDA guidelines, before disc surgery, individuals must have undergone at least 6 months of treatment, such as physical therapy, pain medication, or wearing a back brace, without showing improvement, and must be in overall good health with no signs of infection, osteoporosis or arthritis.
Experts stress the importance of making sure a patient is the right candidate for this surgery. According to Dr Stephen Hochschler and Dr Paul McAfee, examples of how inappropriate patient selection can have serious consequences are:
"If a patient receives an artificial disc, but the disc that was replaced was not actually the cause of the patient's pain, then the patient will have undergone an extensive, invasive and costly procedure but still have the same level of pain. This may seem like an incredibly obvious point, but with back pain it is often difficult to pinpoint the precise cause of a patient's pain. Accurate and careful diagnosis of the patient's pain generator is crucial and cannot be overemphasized.
"If the patient does have a painful disc, but other factors (such as significant degenerative changes in the facet joint) are present, then the patient may have to undergo a revision surgery after the initial surgery to either correct the placement of the disc or fuse the spine-a situation that is definitely best avoided by correctly assessing all the risk factors prior to the first surgery."
Many critics contend that the Chirate disc is just as big a threat to patients as the problems it is supposed to cure. The disc has been promoted as an alternative to fusion; yet, even in the short term studies, spontaneous and surgical fusion occurred.
The disc is required to function for many years, but information about long term benefits and risks, such as satisfaction, adjacent segment problems, and rate of re-operations, is not available because only one short term study, with a 24 month follow-up, was presented to the FDA when the disc was approved.
And even that study has come under attack because the benefits of the Charite in the context of a noninferiority trial, were shown to be noninferior to Bagby and Kuslich cages (BAK), used in spinal fusion, a failed procedure critics say that has not been performed in years.
The 2- year trial showed only that the disc was no worse than this specific type of spinal fusion surgery, according to a May 2005 FDA report.
Overall, the study found that 57% of Charite patients achieved "overall clinical success," compared with 47% of the spinal fusion patients. However, more than 3 out of 5 Charite patients, deemed successes, were still taking narcotic painkillers 24 months after surgery.
In addition, a higher number of Charite patients suffered severe or life-threatening events than spinal fusion patients, 15% compared to 9%, according to the FDA review.
Clinical success in the trial was defined by four criteria: (1) more than 25% improvement at 24 months after surgery, (2) no device failure, (3) no major complication, and (4) and no neurologic deterioration.