Impact of infrared laser light-induced ablation at different wavelengths on bovine intervertebral disc ex vivo: Evaluation with magnetic resonance imaging and histology

Background and Objective Percutaneous laser disc decompression is commonly used to lower high pressure in the nucleus pulposus in degenerative disc diseases. The aim of this study was to investigate the impact of diode laser disc decompression at different wavelengths (980‐nm vs. 1,470‐nm, i.e., different water absorption characteristics). Materials and Methods To model decompression, a flexible laser quartz fiber inserted into the nucleus pulposus of ex vivo bovine spines using computer‐assisted surgical navigation was utilized to vaporize tissue. The same energy (500 J) was delivered using both 980‐nm and 1,470‐nm wavelength lasers. To determine the different impact of the wavelengths before and after the procedure we evaluated the discs with MRI (T1, T2, diffusion maps) and with histopathology. Results There were no visible changes on T1 and T2 maps after 1,470‐nm wavelength laser irradiation; however, the 980‐nm wavelength caused significant changes on T1 (decrease) and T2 (increase) in the vaporization zone at the site of the quartz fiber. Pathological findings showed carbonization and steam‐bubble formation in addition to the T1 and T2 changes. No significant changes were detected in the value of apparent diffusion coefficient (ADC) measurements in intervertebral disc with the 980‐nm wavelength, but significant ADC and T1 signal increase was detected with the 1,470‐nm wavelength when the whole nucleus pulposus was considered. Conclusion The 1,470‐nm laser light had an effect in the whole nucleus pulposus and not only at the site of the quartz fiber, whereas with the 980‐nm laser irradiation, significant changes were demonstrated only at the application site. Lasers Surg. Med. 44: 406–412, 2012. © 2012 Wiley Periodicals, Inc.