Demonstration of laser-induced stress relaxation in cartilage in 1992 led to the development of a novel laser surgical procedure in otolaryngology for the non-ablative reshaping of cartilage. Follow-up studies found that non-destructive laser irradiation may activate regeneration processes in cartilaginous tissue. Ongoing studies seek to characterize the physical, chemical and biological processes and mechanisms involved in the reshaping and regeneration of deformed and diseased cartilage under moderate laser heating. A theoretical model is developed considering laser-induced stress relaxation in cartilage as a process of micropore formation. Results obtained provide scientific and engineering data for development of novel laser surgical procedures for correction of the nasal septum and treatment of spine disc cartilage diseases. This review is aimed to present state of art and recent results in laser -induced reshaping and regeneration of cartilage.Histological cross-section of porcine nasal septal cartilage after laser reshaping using 1.56 µm laser radiation with power of 1.5 W, spot diameter 2 mm, exposure time of 5 s. Stained with Hematoxylin and Eosin, ×400

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The time course and dose dependencies of the observed collagen changes at different levels of its hierarchy further contribute to elucidating the role of connective tissue in the radiotherapy process.

Abstract:The effects of non-destructive laser irradiation on the structure and molecular processes in cartilage were studied using Raman microscopy, differential scanning calorimetry and biochemical analysis. A structural reorganization of the irradiated tissue similar to poliginization in polycrystalline solids was observed for the first time in a cartilage matrix. The difference in the Raman spectra of the irradiated and control samples was interpreted in term of a conformational alteration of glycosaminoglycan macromolecules in the reshaping mode. Laser induced modification of collagen macromolecules was not revealed by Raman spectroscopy. Thermal and biochemical analysis confirmed a preservation of triple helix for laser settings used for laserinduced stress relaxation and reshaping of cartilage.Microphotograph of the Group 3 sample with the two particles. Original magnification ×100, scale bar = 20 µm

The purpose of this study was to characterize essential changes in the structure of annulus fibrosus (AF) after hydrothermal and infrared (IR) laser treatment and to correlate these results with alterations in tissue state. Polarization-sensitive optical coherence tomography imaging was used to measure collagen birefringence in AF. Differential scanning calorimetry was used as a complementary technique, providing detailed information on thermodynamic processes in the tissue. Birefringence, peak of the denaturation endotherm, and the enthalpy of denaturation (DeltaHm) were determined before and after hydrothermal heat treatment (85 degrees C for 15 min) and non-ablative Er:glass fiber laser exposures on AF in the whole disk (vertebrae-disk-vertebrae complex). Our data have demonstrated quantitative differences between results of laser and hydrothermal heating. Birefringence did not disappear and DeltaHm did not change after treatment in the water bath, but loss of birefringence and a decrease in the enthalpy did occur after laser exposure. These results could be explained by the photomechanical effect of laser irradiation. We suggest that thermo-mechanical stress played a dominant role in the disruption of the collagen network of AF under non-homogeneous laser heating.