ChRonIC InstAbIlIty AnD fusIon suRgeRy In LUMBAR DEJENERATIVE DIsC DIseAse

Discogenic pain is closely related to degenerative disc disease (DDD). The source of low back pain is internal disruption of the lumbar intervertebral disc. Chronic segmental instability, mechanical irritation of sensory nociceptive terminals and biochemically activation of inflamatory mediators are thought as causes of discogenic low back pain. Acute and chronic spinal instability are known as important causes of low back pain. Chronic instability is usually associated with degenerative disease or the long term sequale of trauma, tumor or infection. Chronic instability is accepted as the main problem in lumbar DDD but its clinical and radiological festures are poorly defined. The lumbar instability can be divided into two groups as a clinical (functional) and biomechanical (radiographic) instability. Clinical instability is defined that the degeneration of disc is caused to pain depending on the instability. However there is no radiological findings as angulation or certain degree of listhesis. Degeneration is the disruption of the stable structure of disc which leads to the back pain. The definition of biomechanical instability is used when the disc degeneration, translation and angulation are found on radiologic studies of patients. If there is an intervertebral angulation greater than 15* and a vertebral translation greater than 4 mm on dynamic radiographs, an instability should be thought. 1) Clinical findings and differential diagnosis