Laser photoirradiation in digital flexor tendon repair

This study evaluates tendon coaptation using Nd:YAG laser photoirradiation in an in vivo cockerel model. Using the intervinculum segments of the flexor profundus tendons, experimental transactions were performed. Tendon coaptation was then attempted using laser photoirradiation. Tendons were immediately examined for evidence of stable coaptation. After this assessment, specimens were excised and processed for electron microscopic examination and exposure to trypsin digestion. Despite varying multiple laser parameters, tissue welding was not observed. The subsequent functional and ultrastructural observations of irradiated tendon suggest that these changes are those of simple thermal denaturation. The results of this study suggest that when successful tissue welding has been observed in other tissue types, the mechanism is unlikely to be because of formation of intermolecular collagen bonds as hypothesized. An alternative hypothesis is that laser welding reflects photothermal coagulation of cytoplasmic peptides or nucleic acids liberated at the coaptation interface. This may explain the successful welding of cell-rich tissues such as bowel, vas deferens, and arteries and the observed failure of laser welding in collagen-rich but relatively hypocellular tendon.