COMPARATIVE-STUDY OF SURFACE DISPLACEMENT IN DISCS FOLLOWING CHEMONUCLEOLYSIS AND LASERNUCLEOTOMY

Background and Objective: Dynamic changes of the dorsolateral protrusi on site have been postulated to play an important role in the therapeu tic effect of lasernucleotomy and chemonucleolysis. Basic biomechanica l effects of the anulus after lasernucleotomy and chemonucleolysis are investigated. Study Design/Materials and Methods: This study evaluate s the in vitro bulging of lumbar discs comparing lasernucleotomy and c hemonucleolysis. The horizontal displacement at the ventral and dorsol ateral surface of 20 cadaver discs were tested by application of a con tinuously increasing axial deformation before and after therapy. The i ncrease in horizontal displacement due to this longitudinal deformatio n was measured. Results: Bulging was significantly lower at the punctu re site of the chemonucleolysis needle as well as at that of the laser trocar. Significantly reduced bulging of the anulus was observed afte r chemonucleolysis. Slightly increased bulging was observed after lase rnucleotomy in the total posterior region. There was a tendency to dec reased stiffness after chemonucleolysis and a significantly decreased stiffness after lasernucleotomy. Conclusions: The in vitro effect of l asernucleotomy seems to be based on reduction of the stiffness by dist ributing the load all over the anulus, whereas chemonucleolysis reduce s bulging. (C) 1998 Wiley-Liss, Inc.