CHANGES OF THE LUMBAR DISC AFTER THE USE OF HOLMIUM-YAG LASER - A BIOCHEMANICAL STUDY

For a biomechanical study 10 specimen of the lumbar spine (L1-S1) were scanned with MRI. After that 18 normal motion segments were prepared for the experiments. The paraspinal musculature as well as the posteri or elements were removed. Under an axial load of 500 N, in each disc 5 00 J and 1000 J of energy were applicated with a Holmium-Yag laser (20 60 nm, fiber thickness 600 mum) into the nucleus pulposus. In nine of the 18 discs also 1500 J and 2000 J were applicated. At the beginning of every standardized experiment of a motion segment, as well as after every 500 J, the height of the disc, intradiscal pressure, the contou r of the disc and the size of the transversal plane of the disc were d etermined with an axial load on the motion segment of 1000 N. The chan ge in radial bulging of the disc was measured using the computer-assis ted recordings of each disc contour. All the data were statistically a nalyzed using the Friedman-/Wilcoxon-test. After every application of 500 J energy, in the 18 discs as well as in the 9 discs, the height an d the intradiscal pressure reduced. The differences per 500 J were for all measurements not significant (p < 0.05). Up till the application of 1500 J the radial bulge and the size of the transversal plane of th e disc increased, although the differences per 500 J were not signific ant. From 1500 J to 2000 J the radial bulge and size of transversal pl ane of the disc decreased. However, statistical analysis showed no sig nificance with the changes under 1500 J. With regard to the results of this study and a biomechanical study of the changes of the disc after non-automated percutaneous lumbar discectomy, a hypothesis is made, h ow the mechanism of reducing radicular symptoms after percutaneous nuc leotomy in vivo can be explained.