Morphologic changes in collagen fibers after 830 nm diode laser welding

BACKGROUND AND OBJECTIVE: The mechanism of laser tissue welding is elusive, but collagen transitions are somehow involved. Collagen fiber modifications observed after 830 nm diode laser welding are presented in this study. STUDY DESIGN/MATERIALS AND METHODS: A 830 nm diode laser assisted longitudinal aortorrhaphy was performed on 37 Wistar rats, with shots of 0.5 W in power, 8 sec in duration and 250 W/cm2 in irradiance. Energy utilized ranged from 400-550 J/ mm2 for 1 cm-length of anastomosis. After laser welding, histological modifications in collagen fibers were observed through optic, scanning electron, and electron microscopic examination. RESULTS: After laser welding, collagen fibers lost a proportion of birefringence. Under electron microscope, the different changes in collagen fibers were visualized being either fused, "roped," swollen, or dissolved, surrounded by normal ones situated in the same zone. CONCLUSION: These data suggest that diode laser heating denatured part of the collagenic fibers, and that these morphologic changes play an important role in laser welding.