Artificial Discs: An Editorial

The day before the start of the annual North American Spine Society meeting in Chicago on October 27, 2004 the United States Food and Drug Administration announced its approval of the first artificial lumbar spine disc implant, the Johnson and Johnson owned Link SB Charité (shown below).  Click here for more information on artificial discs.

With this nod from the American government the American spine surgical device industry went into high gear to media market blitz to promote these devices.   The hype for artificial discs has also attracted thousands of spine surgeons.  These devotees of "medicine by marketing" were not therefore disappointed by the resulting overwhelming initial public response requesting this device for the treatment of essentially all spine problems.

The intense world-wide business interest in artificial disc devices was   reflected by the purchase, aquisition in early 2003, by Synthes-Stratec of Spine Solutions, Inc. (the developer of ProDisc) for $350 million and the purchase agreement by DePuy Acromed (a Johnson and Johnson Company) for Link Spine Group, Inc. (the developer of the Charité) for a similar amount. Investment analysts had predicted that artificial discs could become a billion dollar market by the year 2010.

There can no question but that "artificial disc" technology concept represents a  much more physiologic approach to spine stabilization rather than rigid multi-level instrumented "fusions" being performed indiscriminately on patients with back pain.  The key question has been however whether or not this technology (at its most early stage of development) provides reasonable benefit when compared to the associated level of  patient risk.  Fortunately, important information has now been provided by experienced spine surgeons in regard to examining this risk.   At the American College of Spine Surgery Review Course, Sept. 22-26, 2004 Course Chairman David McCord made an important statement.  He said "I never do a surgery that I can't also salvage."  It is extremely difficult  to salvage a Charité artificial disc or others similar to it if things go wrong.  On June 2, 2004 Orthopedic surgeon John Peloza, in his testimony to the FDA Orthopedic and Rehabilitation Devices Panel testified: "I think it is critical that these implants last for the life of the patients, because revision surgery to remove the implant particular (sic) from an anterior approach will be potentially life threatening in every case." Of further concern, is the letter to the Editors of the North American Spine Society publication SpineLine by spine surgeon André van Ooij of the Netherlands, who has observed, in significant numbers of post-artificial disc implants in Europe that: "These patients represent the most disabled group of patients that I have personally have seen in 24 years of spine practice."  Dr. Ooij also expressed concern regarding overload of the facet joints as a consequence of removal of the anterior longitudinal ligament and anulus fibrosis producing axial rotational instability and related progressive degeneration of the facet joints.  In 2007 Orthopedic Surgeon Charles Rosen and his associates from the University of California (UCI) Spine Center published a paper designed to explain this high failure rate of lumbar artificial discs.  To begin with they found that the data presented to the FDA was biased and flawed and that the devices themselves were based on a faulty biomechanical model.   In addition to this important information regarding the inherent liabilities of the lumbar implant it is important to review of what criteria the  FDA approval of the Charité disc was based on.  These were: ◘ For use at one lumbar level, L4 through S1. ◘ For use in patients with back pain who have failed at least 6         months of conservative (non-surgical) therapy. ◘ Other exclusion criteria include more than two symptomatic diseased levels, known allergy to the implant components, prior lumbar fusion surgery, clinically compromised vertebral bodies from trauma, clinically significant facet disease, lytic spondylolisthesis or spinal stenosis, degenerative spondylolisthesis greater than G1, pain that defies diagnosis, osteoporosis, metabolic bone disease (including Paget's, osteomalacia), or small vertebral bodies.

The success of any surgical procedure is primarily dependent on good patient selection.  In all candor, there are precious few patients out there being provided with lumbar artificial discs who really meet the FDA criteria for surgery.  In addition, few patients are provided with 6 months of modern and effective conservative care modalities which, in the Editor's opinion, are much more likely to effectively treat the patient than any of the the surgical options presently being used.  Personal experience with attempting to salvage lumbar artificial disc failures to date has continued to support the Editor's concern regarding poor patient selection as well as failing to provide the patient with true informed consent.  Many of these devices have been implanted in chronic smokers, individuals with multilevel degenerative disease (often on a genomic basis), and patients with unaddressed nerve compression problems have only to served to indicate that the initial clinical results from this new technology at its entry level of development have been akin to a public health hazard. Unlike other body artificial joints which are readily amenable to replacement the same is not true for lumbar artificial discs. Despite this sad situation in regard to first generation lumbar artificial discs there is some bright light beginning to appear with the introduction of cervical artificial discs where they do indeed, at this time, appear to represent something of value for carefully selected patients. Charles V. Burton, M.D. Editor, Burton Report

Click Here for More Information  on Artificial Discs