gms | German Medical Science

Objective: Laser ablation of ligamentum flavum could be an interesting alternative to the established mechanical procedures in the treatment of lumbar spinal stenosis. The object of our series of investigation was to define the nature of removal of ligamentum flavum by CO₂-laser ablation in terms of three characteristics: first, the histological characteristics of tissue removal and the possible evidence of thermal damage second, the effect of additional water-spray on thermal side effects and ablation efficacy and third, the quantification of effectiveness of ablation by measuring the ablated tissue volume over time.

Methods: Experiments were performed on ligamentum flavum harvested from spinal segments L3/L4 and L4/L5 obtained from 5 fresh human cadavers. A commercial SC x 30 CO₂ laser (λ=10,6 µm) from Rofin-Sinar was used for all experiments. The used pulse duration was 44 µs and 56 µs. Irradiation was performed with or without water-spray. The average power at a repetition rate of f_laser=50 Hz was 3,2 and 1,8 W. Lased samples were processed for H&E staining and histological examination. Digital pictures from histological slices were obtained and analysed with a graphical software to perform computed surface measurements and calculate ablation volumes.

Results: Dry irradiation causes significant thermal side effects whereas only minimal collateral damage is observed when an additional waterspray is applied. The use of an additional water spray does not only reduce thermal side effects significantly but also increases effectiveness of the ablation process. With an average laser power of 3,2 W used in our experimental setting a volume of 1 cm³ is ablated in 60 minutes.

Conclusions: Our data show that short-pulsed CO₂-laser ablation at 10,6µm with the use of an additional waterspray could be an effective tool to ablate human ligamentum flavum without significant thermal damage to the surrounding tissue layers.