Artificial Disc Replacement: Randomized Clinical Trial Update

Years ago, painful hip and knee joints were fused. While this may have provided varying levels of pain relief, it also eliminated joint motion. Today, hip and knee replacements using motion-retaining implants are commonplace. Traditionally, spinal fusion has been performed to treat pain related to the intervertebral disc. However, motion-retaining spinal implants are now being evaluated in the United States to relieve pain and allow motion of the spinal segment being treated. The potential benefit of such devices allows earlier participation in post-operative rehabilitation and activities and reduces stress to adjacent joints. When a joint is fused the adjacent joints must carry the stress passed through the fused segment. Long-term, this may result in a more rapid and possibly painful deterioration of adjacent segments.

Currently, there are four total artificial discs being evaluated by the Food and Drug Administration (FDA) in FDA-regulated clinical trials in the United States. The randomized clinical trial for one of the devices, the Charité™ Artificial Disc (manufactured by DePuy Spine, Inc.) has been completed and the study results have been submitted to the FDA with approval pending.

Charité™ Artificial Disc Randomized Study
The Charité™ Artificial Disc (manufactured by DePuy Spine, Inc.) study involved 304 patients enrolled from 15 centers. After five training cases were completed at each center, patients were enrolled in a randomized study using a 2:1 assignment ratio of artificial disc to anterior lumbar interbody fusion. This means that for every two patients receiving the artificial disc, one patient received fusion. All cases were performed at a single lumbar disc level. Patients were followed for 24 months to determine their outcome.

At the annual meeting of The Spine Arthroplasty Society, the Texas Back Institute, the principal study investigating center summarized the study results. Outcome measures used in the study included a 0 to 10 scale to assess pain intensity, a questionnaire that asked patients about their daily activities (Oswestry Low Back Pain Disability Questionnaire), and during 12- and 24-month follow-up visits patients were asked how satisfied they were with their outcome and if they would undergo the same treatment again. In both the artificial disc replacement and the fusion groups, pain and functional scores improved significantly after surgery. At most follow-up periods, the improvements were significantly greater in the artificial disc group compared to the fusion group. Responses to the questions assessinging satisfaction and if the patient would elect to have the same surgery again, indicated a trend favoring total disc replacement. Complications associated with the artificial disc were similar to those encountered with spinal fusion.

ProDisc®
Although data collection is on-going at the Texas Back Institute (TBI) for the ProDisc® (manufactured by Synthes Spine), TBI's preliminary results are available. This randomized study was designed for patients to receive either the ProDisc® or a combined anterior/posterior spinal fusion. Patients with symptomatic disc degeneration at one or two lumbar disc levels were included. The results were similar to those of the Charité™ in that both groups showed improvement in pain and self-reported function. At some follow-up periods, the improvements were greater in the ProDisc® group. Patients indicated a high level of satisfaction with their results. A 24-month data collection is on-going.

New Solutions for Back Pain
Now is an exciting time to be treating patients with back pain. The Texas Back Institute is involved in the evaluation of several spinal devices and surgical systems. These new products include three total lumbar disc replacement devices, one cervical disc replacement device, a posterior dynamic stabilization device, minimally invasive surgical and guided imaging systems, and pharmaceutical agents.

In the near future, we will participate in clinical trials to evaluate disc nucleus replacements, newly designed posterior devices, and facet joint replacements. These treatments will provide the basis for less invasive procedures to allow the spine to retain its normal movement as much as possible.

Changes are Evolutionary
Although the occurring changes have been in an evolutionary phase for quite some time, it is important that proper education is well-organized for patients, surgeons and other providers to prevent over-utilization of these technologies and to help avoid potential complications. The Spine Arthroplasty Society has taken on this educational mandate and plans to work with physicians, industry and hospitals for the benefit of our patients.