PHILADELPHIA, PA – September 2005 - A revolution may be under way in spine care, and it can be summed up in three words: total disc replacement (TDR). For the first time, surgeons have the ability to employ spinal implants that preserve the natural mobility of the spine.

But this revolution has encountered unexpected resistance from some clinicians and payers, who worry about the long-term durability of artificial discs and the degree to which repeat surgery can address device failures and complications. Some have even suggested that surgery to replace faulty discs might pose potentially life-threatening dangers.

However, a new study offers the reassuring conclusion that early surgical failures can be safely corrected in a second operation.

“Lumbar TDR with the Charité artificial disc did not ‘burn any bridges,’ ” said one of the study’s coauthors, Paul McAfee, MD, of the Spine and Scoliosis Center in Towson, MD. McAfee presented his findings on Wednesday, September 28, at the 20th annual meeting of the North American Spine Society in Philadelphia.

The Food and Drug Administration approved the Charité artificial disc in October 2004 for single-level disc disease in adults. After it reviewed a large clinical trial that compared disc replacement to spinal fusion with the BAK fusion cage, the FDA concluded that patients in both groups derived roughly equal improvements in pain and function: 57% of total disc replacement patients met the FDA’s criteria for success versus 46% of patients who underwent fusion. (Blumenthal S, Spine, 2005; 30:1565-15755.)

The Charité disc comprises a sliding polyethylene core sandwiched between two metal endplates. It was created to address limitations inherent in spinal fusions, which reduce motion in the spine and may accelerate spinal degeneration. Disc replacement is intended to preserve spinal motion and, in theory, prevent degeneration in adjacent anatomy.

McAfee and his colleagues reviewed 27 reoperations that occurred among 347 patients who underwent disc replacement during the FDA pivotal trial and a cohort study that accompanied it. The overall revision rate was 7.8%.

The average time interval between the initial operation and the reoperation was brief, about six months, according to McAfee. Fifteen patients underwent disc removal. Five received a second artificial disc, and the remainder underwent a different form of surgical stabilization. A number of patients underwent exploratory surgery that did not result in removal of the artifical disc.

McAfee, a coauthor of the FDA-regulated randomized controlled trial, said that about 4% of reoperations were attributable to failures of the implant itself. The two principal reasons for failures were patient selection errors and technical mistakes. Some individuals who shouldn’t have received the artificial disc did—including men and women with lumbar fractures (pars defects) and instability (spondylolisthesis), overlooked during the initial diagnostic process.

In addition, some surgeons who implanted the devices erred in placement and technique; they had problems using fluoroscopy to guide their procedures and failed to center the device in the disc space, said McAfee. The most common mistake was placing the prosthetic disc too far forward in the spine, creating unnatural motion and pain.

This study will not end the debate over the durability of disc replacement or the feasibility of revision surgery. Research to date has been conflicting. One recent study by Jean-Philippe Lemaire, MD, and colleagues reported revision rates similar to those described by McAfee among 107 patients followed for a minimum of 10 years. (Lemaire JP et al., J Spinal Disord Tech, 2005; 18:353-9.) However, a study presented by British researchers earlier this year found a much higher revision rate (45%) among 160 patients studied for up to 13 years. (Khatri M et al., presented at the International Society for the Study of the Lumbar Spine, New York, 2005.)

Is TDR ready for widespread use in the community? According to one recent estimate, hundreds of surgeons in the U.S. have been trained over the past year. Will their results be comparable, better, or worse than those documented in the FDA-regulated trials? FDA trials, after all, involve some of the best surgeons in the field.

How much practice should surgeons have before they consider themselves proficient in the procedure? Estimates vary widely. McAfee says five training cases is enough. However, spine surgeon Fred Geisler, MD, a coauthor of the FDA-regulated trial, suggests that disc replacement is one of the most challenging procedures in spine surgery, particularly for surgeons who are not experienced in anterior procedures. (Geisler F, J Neuros (Spine), 2004; 1:143-154.)

The North American Spine Society recently issued training recommendations for TDR. They include the following:

• The surgeon should have extensive experience in anterior lumbar interbody fusion. The risks inherent in an anterior transperitoneal or retroperitoneal approach-- and, particularly, in a repeat anterior approach—“are significant.”
• The clinical setting should be equipped to deal with potential intra-operative and postoperative complications.
• Surgeons should be accomplished in the possible salvage procedures.
• Surgeons should have performed one to two ARD procedures per month for the preceding 12 months; be proficient with fluoroscopy; be certified in a training course given by the offering technology company; and first undergo a series of mentored operations.

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NASS is a multidisciplinary medical organization dedicated to fostering the highest quality, evidence-based, and ethical spine care by promoting education, research, and advocacy. Since its start in 1985, NASS has grown to nearly 4,000 members in 22 spine-related specialties. NASS members are MDs, DOs, and PhDs, including orthopedics, neurosurgery, physiatry, pain management, and other disciplines. Nurse practitioners, physician’s assistants, chiropractors, physical therapists, practice administrators, and other allied health care professionals involved in spine care are also represented as affiliate members.

For further information, contact:
North American Spine Society
Toll-free: (866) 960-6277   Direct: (630) 230-3600