Quantitative determination of ablation in weight of lumbar intervertebral discs with holmium: YAG laser
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1Spine Unit, Clinic Balgrist, University of Zurich Medical School, Switzerland.
Background And Objective:
Since 1992, the Ho:YAG 2100 nm laser has been in regular use in percutaneous lumbar disc surgery through the uniportal approach. In vitro experiments were done to find out the exact amount of ablated tissue in weight per energy used with the present beam delivery system. STUDY DESIGN MATERIALS AND METHODS: Thirty dissected human lumbar discs were treated with the Ho:YAG laser with 12 x 10(6) W/cm2 of effective power density, under 20 ml/min of continuous irrigation. The ablation amount was determined through indirect comparison, using the water content of each disc as reference, which was predetermined individually by freeze drying.
Results:
The ablation of nucleus pulposus is 32.293 mg/kJ in dry weight and 104.719 mg/kJ in physiologic weight. The ablation capacity in annulus fibrosus is 50% of that in nucleus pulposus.
Conclusion:
With 20 kJ of energy, the average amount of energy used in actual operations, the mean ablation of nucleus pulposus is 0.556 + or - 0.06 (n = 3) grams in dry weight, and 1.89667 + or - 0.162 (n = 3) g in physiologic weight.