Ex vivo laser thermoplasty of whole costal cartilages.

BACKGROUND AND OBJECTIVE: To examine the possibilities of laser thermoplasty of whole costal cartilages for correction the human congenital chest wall deformities. STUDY DESIGN/MATERIALS AND METHODS: Ex vivo the samples of porcine costal cartilages were heated with lasers of differing wavelengths, including a 0.97-µm diode laser, a 1.56-µm erbium-doped quartz fiber laser, and a 1.68-µm fiber Raman laser. The dynamics of the temperature fields and the degradation of collagen in the laser-affected regions of samples were determined by using, respectively, thermometry, trypsin treatment, and light microscopy. Ex vivo the whole mechanically deformed costal cartilages of pigs were treated by laser radiation with wavelength 1.68-µm. The changes of cartilage shape were recorded at certain intervals over a 24-hour period by photographing them in a fixed position with a digital camera. RESULTS: Treatment of costal cartilage samples from 5 to 11 mm in thickness by laser radiation with 0.97, 1.56, and 1.68 µm wavelengths showed that the 1.68-µm radiation could produce the necessary nonuniform bulk heating of the exposed sample. The altered shape of costal cartilage proved to remain stable after treatment when the laser irradiation settings used provided for the heating of a broad region within the tissue to temperatures about 80°C. CONCLUSION: This study demonstrates the possibilities of laser thermoplasty of whole costal cartilages for treatment of human congenital chest wall deformities. The development of novel approaches based on laser cartilage engineering techniques will enable to treat the human congenital chest wall deformities.

Laser-induced modification of the patellar ligament tissue: comparative study of structural and optical changes.

The effects of non-ablative infrared (IR) laser treatment of collagenous tissue have been commonly interpreted in terms of collagen denaturation spread over the laser-heated tissue area. In this work, the existing model is refined to account for the recently reported laser-treated tissue heterogeneity and complex collagen degradation pattern using comprehensive optical imaging and calorimetry toolkits. Patella ligament (PL) provided a simple model of type I collagen tissue containing its full structural content from triple-helix molecules to gross architecture. PL ex vivo was subjected to IR laser treatments (laser spot, 1.6 mm) of equal dose, where the tissue temperature reached the collagen denaturation temperature of 60 ± 2°C at the laser spot epicenterin the first regime, and was limited to 67 ± 2°C in the second regime. The collagen network was analyzed versus distance from the epicenter. Experimental characterization of the collagenous tissue at all structural levels included cross-polarization optical coherence tomography, nonlinear optical microscopy, light microscopy/histology, and differential scanning calorimetry. Regressive rearrangement of the PL collagen network was found to spread well outside the laser spot epicenter (>2 mm) and was accompanied by multilevel hierarchical reorganization of collagen. Four zones of distinct optical and morphological properties were identified, all elliptical in shape, and elongated in the direction perpendicular to the PL long axis. Although the collagen transformation into a random-coil molecular structure was occasionally observed, it was mechanical integrity of the supramolecular structures that was primarily compromised. We found that the structural rearrangement of the collagen network related primarily to the heat-induced thermo-mechanical effects rather than molecular unfolding. The current body of evidence supports the notion that the supramolecular collagen structure suffered degradation of various degrees, which gave rise to the observed zonal character of the laser-treated lesion.

IR laser and heat-induced changes in annulus fibrosus collagen structure.

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.