Spondylolisthesis has been known since the 18th century. At the begining, various treatment methods have been applied. Some used posterior and posterolateral fusion (1, 2, 10); later interbody fusion has been tried. (1, 3)
Harrington was the first One in 1969 who applied reduction and stabilization throgh internai fixation (8). Subse-quent works by others consisted mainly of the adaptation of Harrington's instrumentation to their own methods. Later on Dwyer pioneerd stabilization through transpediculer screw. This method has further been developed by Cotrell and Dick (7).
Biomecanical studies showed that in lumbar vertebras the trans pedicular screw systhem is the best one for rigid fixation and immobilizition (6, 7, 11).