The Artificial Disc

Low back pain due to degenerative disc disease is a very common problem. It is estimated that 80% of our population will have at least one episode of severe back pain during their life. Between 2 to 5% of the working population will suffer disability due to back pain and about 50% of these will be permanently disabled to some degree. Most patients will respond to non-operative treatment. For the occasional patients who do not respond to non-operative treatment surgery is considered. The mainstay of surgical treatment to date has been spinal fusion. This procedure involves fusing or "gluing together" adjacent vertebra so they no longer move. In highly selected patients the outcome for pain relief is 70 to 80%. However, fusion is not a physiologic condition. Even in patients who obtain pain relief initially late pain can arise due to progressive degeneration of the unfused levels of the spine. This is termed adjacent level degeneration. Pain relief can also be affected by the presence of metallic hardware used to obtain fusion and by an unhealed fusion (non union).

Lumbar disc replacement is an attempt to eliminate the "late complications" of spinal fusion. Theoretically, replacing the disc maintains the motion of the space between the vertebrae, but still removes the anatomic reasons for pain. Since motion is maintained there would be less risk of adjacent level accelerated degeneration.

The current artificial discs in use today are either composed of metal and plastic or me!al plone. They are inserted though a frontal approach to the spine called the retroperitoneal approach. There is,extensive experience in Europe and Asia with these procedure? At this time/use of these implants in the United States has been limited to experimental studies. It is expected that in the last quarter of 2004 the first artificial disc will be approved for use in the United States. This device, called the SB Charite, has been placed in over 8000 patients in Europe since 1987. Good outcomes have been reported in approximately 80% of the patients.

Primary indications for the device have been single level symptomatic lumbar disc disease, failure to respond to nonoperative measures over a six month period, re-creation of pain on discography, absence of neurological symptoms and nerve compression, and mini mal arthritis of the facet joints of the spine.

There are complications that can be associated with the artificial disc. These include persistent pain, abnormal wear of the implant, infection, and displacement of the device. Displacement of the artificial disc is a serious concern because it can impinge on the vascular or neurological structures.

It must be stressed that the artificial disc is not a .cure all" for back pain. We still need more information in regards to the long-term effects and outcomes associated with these devices. However, it does appear, based on the early studies, that the use of the artificial disc in highly selected patients can be beneficial.

Dr. Schneiderman is a graduate of Loyola University Medical School. He completed his residency at USC and spine fellowship training at Ker/an-lobe Orthopedic Clinic. He is certified by the American Board of Orthopedic Surgery.