THE ARTIFICIAL DISC - THEORY, DESIGN AND MATERIALS

Low back pain is one of the most common medical conditions in the West ern world. Disc degeneration, an inevitable process of aging, of varia ble rate and degree, is one of the major causes of low back pain. Curr ently, there are two major surgical interventions for treating conditi ons related to the degenerative disc: discectomy and fusion. Although discectomy and fusion produce a relatively good short-term clinical re sult in relieving pain, both these surgical treatments alter the biome chanics of the spine, possibly leading to further degeneration of the surrounding tissues and the discs at adjacent levels. Over the past 35 years, a tremendous effort has been made to develop an artificial dis c to replace the degenerated disc. The goal is the restoration of the natural biomechanics of the segment after disc excision, thus relievin g pain and preventing further degeneration at adjacent segments. Howev er, the artificial disc faces a complex biomechanical environment whic h makes replication of the biomechanics difficult and long-term surviv al challenging to designs and materials. The purpose of this article i s to examine the factors of importance in designing a disc replacement . Topics covered include the structure and function of the natural dis c, the changes that occur with disc degeneration and existing methods of treatment for the degenerative spine. The progress in achieving a f unctional, long-lasting disc replacement is outlined. (C) 1996 Elsevie r Science Limited.