ABSTRACT
For degenerative lumbar instability, various spinal instrumentations have been used to relieve clinical symptom and to stabilize the spine. Most of them are rigid fixation which cause a postfusion instability at adjacent segment with high incidence. It creates a highly susceptible region(neo-hinge) between fixed rigid segment and nonfixed mobile segment. Eventually acceleration of degenerative change in adjacent segment is resulted with clinical deterioration. To avoid of postfusion instability after rigid fixation, a semi-rigid fixation system which has a intermediate transitional zone is developed. In 98 patients with degenerative lumbar instability, semi-rigid fixation which had a damper in the middle of plate were performed with CH titanium cage. Angular instability in lateral dynamic X-ray was improved in all case immediately after operation. Translational instability also much improved. But no degenerative change or instability in adjacent segment(neo-hinge disc) or overlying disc within fusion segment during follow up period of average 16 months. Excellent and good clinical results were achieved in 90.8% of patients and the solid bone fusion was occurred in 98.9%.