"1) only 57% of disc replacement patients and 46% of BAK fusion patients met these four limited criteria; 2) in patients who were considered a clinical success at 24 months, 64% of the Charite group and 80.4% of the control were using narcotics; 3) at 24 months the change in VAS and ODI did not differ statistically from control; 4) the SF-36 PCS and MCS composite scores did not differ statistically from control; 5) no difference in operative time or blood loss between the two groups."
According to the CMS Memorandum, the surgical procedure for disc replacement involves an anterior approach for exposure of the spine. With this approach, complications of vessel injury can occur and have the potential to be life threatening (Santos, Polly et al. 2004). As to revision surgery, Santos, et al, state:
"Revision 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."
In recent years, the cost benefit of surgery for degenerative disc disease has come under scrutiny. The 2005 Cochrane review of surgery for degenerative lumbar spondylosis states, "There is no good evidence on cost-effectiveness" (Gibson, Wassell 2005).
Concern over the cost benefit has been expressed specifically for the artificial disc. Within 5 years of its release, the CMS noted, it was predicted that spinal arthroplasty (lumbar and cervical) could reach an annual cost of $2.18 billion in the US, with the suggestion by Singh that this estimate is conservative (Singh, Vaccaro et al. 2004).
Santos stated, "...long-term clinical outcome using validated instruments are necessary to justify the added cost of these procedures."
Dr Sohail Mirza, a medical professor at the University of Washington, criticized Charite's marketing slogan of "natural motion is back." It "implies that the artificial disc creates a normal spine; it does not," he stated last year in the journal Spine.
"Contrary to optimistic marketing, the data," he wrote, "argue for caution by patients and surgeons. Hope for a cure of back pain and a marketing bonanza must be held in check."
As of July 2006, more than 130 serious adverse events have been reported to the FDA associated with the Chirate disc.
In 2005, the FDA performed an analysis of adverse events reported in the Manufacturer and User Facility Device Experience Database (MAUDE), at the request of CMS. The analysis includes Medical Device Reports (MDRs) that were entered into the database between August 11, 2003 (first report received) and November 16, 2005.
A total of 101 MDRs were analyzed for 96 patients, with 1 MDR for the Prodisc device in addition to the Charite devices.
The most frequently reported event was device migration out of the implanted location, with 54 of 96 patients (56%) experiencing this effect. Seventy-six patients (79%) had a second surgery to remove all or part of the implant, to correct problems with the device, or to correct problems produced during the surgery. Fifty of the 76 (66%) patients had second surgery due to device migration.
The most common second surgery was to remove all or part of the disc followed by spinal fusion of the implanted motion segment. Twelve patients had 2 prostheses placed despite the device labeling for only one device implantation. Most adverse events that required second surgery occurred in the first 2 months after implantation. Two deaths were reported which were both attributed to pulmonary emboli.
Dr Charles Rosen, associate clinical professor of spine surgery at the University of California, Irvine, told the LA Times on August 5, 2006, that he has seen 10 patients since late last year, complaining of worsening pain after receiving the Charite disc and that some patients suffered fracturing and an abnormal pulling apart of the joints of the spine.
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