The Lumbar Artificial Disc

History of spinal fusions:

The treatment of spinal disorders has evolved considerably over the last decade. While spinal deformity has always existed, Polio was the major impetus for the use of spine stabilization devices such as Harrington rods and bone grafts.

Ultimately superior fixation devices were developed which produced more consistent deformity correction and stability of the spine. With modern fixation devices such as screws and rods, the three-dimensional deformity of scoliosis curvature can be greatly corrected in children and adolescents, and moderately corrected and stabilized in adults. The use of rigid metallic fixation devices for scoliosis, spondylolisthesis, trauma, and spinal reconstruction after cancer will continue to be used until the etiology of these disorders is discovered.

Today most of these stabilization devices are utilized to treat age-related degenerative disc disease, and low back pain with nerve compression disorders.

Motion Preservation:

I am frequently asked to lecture on the pros and cons of the artificial disc because of my familiarity with motion preservation literature written nationally and internationally. Throughout my career, I have studied Adjacent Segment Degeneration and technique for maintaining the natural balance of the spine, which is a major consideration in preserving motion of the spine.

The lumbar artificial disc:

Advocates of the lumbar artificial disc argue that spinal fusion has two significant drawbacks. The first argument is that stabilization of the spine inherently reduces the functional capacity of the individual because of decreased spinal motion. Secondly, a transfer of forces to the adjacent segments of a spinal fusion accelerates therefore creating the potential for degeneration and the possibility of future reconstructive surgery. According to their theory, motion preservation technologies for spinal disorders would obviate these two negative consequences of spinal fusion.

Current lumber artificial disc replacement at L5-S1 is rarely indicated for the following reasons. Failure of lumbar disc herniation and need for revision can be life threatening. There is no significant functional motion at L5-S1. Adjacent segment degeneration has been shown to be equal between disc replacement and fusion at L5-S1.

Lumber artificial disc replacement will be subjected to a much steeper learning curve, the short and long-term outcomes may be marginal, and the revision for failed implants will be difficult and at times life-threatening. Current literature suggests that lumber artificial disc replacement when compared to spinal fusion does little to improve overall functional spine motion. Moreover, the current studies indicate when lumber artificial disc replacement is observed for a long period of time, the failure rate is high, and there appears to be little benefit to protecting the adjacent segment as with standard fusion. This leads to a situation where the short-term benefit of the theoretical advantages of lumber artificial disc replacement for motion preservation may lead to significant long-term problems.

These findings suggest that the lumbar spine is subjected to significant forces which put high mechanical stress on these implants leading to their failure. From an anatomical standpoint, failure of lumber artificial disc replacement may have serious consequences. The anterior part of the spine lies behind large vessels and intra abdominal structures which make it difficult to reach after the first operation is performed.

The Future:

Hopefully in the not-too-distant future gene therapy technologies will be applied so that the patient's own disc can be reconstituted and restored to its natural function. In the meantime, fusion or artificial disc devices will be used in clinical trials to treat these conditions.

In the News:

Dr. Pashman agrees with the conclusions rendered by Medicare in these articles:

New York Times Examines Johnson & Johnson's Efforts To Obtain Medicare Coverage for Implantable Spinal Disk, Mar 20, 2006

CMS Proposes To Deny Medicare Coverage for Johnson & Johnson Artificial Spinal Disk, Feb. 17, 2006