ABSTRACT
Approximately one percent of the U.S. population is chronically disabled because of back pain and an additional one percent is temporarily disabled (1,2). More than 20 million working days are lost each year because of back pain, resulting in financial losses estimated as high as $100 billion per year (1,2). Disorders of the intervertebral disc are a major contributor to these statistics. The conventional treatment for lumbar degenerative disc disease (DDD) involves disc excision with or without fusion. However, fusion techniques do not guarantee satisfactory results. Clinical and biomechanical studies indicate that fusion results in altered kinematics and clinical problems at the adjacent motion segments. To overcome the perceived drawbacks of fusion (static instrumentation), dynamic spinal implants has been developed and used that maintain the natural kinematics of the spine, reestablish clinical stability, and maintain the caliber of neural foramina while avoiding the development of adjacent level degenerative changes.
