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Comparing Artificial Disc Replacement at One- Versus Two-Levels

There have been problems with lumbar fusion for chronic low back pain (LBP). Research is ongoing to develop a long-lasting artificial disc replacement (ADR) to avoid these problems. Right now the FDA has approved the Charité ADR for use at one lumbar level. It has not been cleared for two-level use yet.

In this study, researchers used a computer-simulated model to compare results using a one-level ADR versus a two-level ADR. The one-level ADR also had a one-level fusion at the level below. The fusion was also simulated using a cage and pedicle screw system. The authors describe the simulation process in detail including software used and special features of each program.

The simulated spinal segments were tested under a variety of conditions and motions. As expected, motion was decreased at the fused segment and increased at the ADR levels. Loads on facet joints at the level of the ADR were decreased. There was no measurable change in disc pressure above or below the ADR segments.

In both cases, motion changed about the same amount at the lumbar level above the segment operated on. The difference was that the motion increased in the fusion/ADR model and decreased in the two-level ADR model.

The authors could not say if one procedure was better than the other. The computer simulation does not include the effect of muscles. Likewise changes that occur during surgery when soft tissues are cut to insert the ADR or cages could not be accounted for. Various tiny micro-motions of the spine present in the live model are also impossible to recreate in a simulated model.

More study is needed to compare fusion with ADRs at different levels and in different combinations. Effect on motion, load, discs, and joints should be measured with each scenario. Both simulated and cadaver studies are important before live studies can be done.


Jonathan N. Grauer, MD, et al. Biomechanics of Two-Level Charité Artificial Disc Placement in Comparison to Fusion Plus Single-Level Disc Placement Combination. In The Spine Journal. November 2006. Vol. 6. No. 6. Pp. 659-666.

11/16/2006

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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