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Dura mater repair represents a final and crucial step in cranial surgery: an inadequate dural reconstruction determines dreadful consequences that significantly increase morbidity and mortality rates. Different dural substitutes have been used with poor results. To overcome this issue, in previous studies we proposed a laser-based approach to the bonding of porcine dura mater, evidencing the feasibility of the laser assisted procedure. In this work, we present the optimization of the laser bonding approach ex vivo in porcine dura mater and in vivo in rats. An 810 nm cw laser was used to weld the ICG stained chitosan patch to the dura. The ex vivo tests enabled to optimize the laser parameters, using histology and leak pressure evaluation to study the bonding effect. The in vivo tests were performed on 32 adult Wistar rats: laser bonding was carried out in 16 rats, while a collagen matrix was used for duroplasty in the control group. After the treatment, the animals were left to recover and were observed in a 15 and 90 days follow up study. At sacrifice, the rats were anesthetized for fluid leakage pressure test; treated tissue was harvested and underwent standard histology. The results of this study pointed out that the laser bonding procedure can be used to close the dura mater, both ex vivo and in vivo. The thermal effect is limited and spatially confined. The technique can thus be proposed as a valid alternative to standard method for the closuring of dura mater in cranial surgery.

Background and study aims The thulium laser system (TLS) is an emerging surgical tool. The 2-μm wavelength provides a confined coagulation depth (0.2 – 0.4 mm) to reduce the potential for inadvertent injuries. For the first time ever, we assessed TLS feasibility for endoscopic hemostasis ex vivo in pigs. In addition, we performed the first in vivo hemostatic treatments in humans. Patients and methods Tissue damage induced by TLS using different settings and optical fibers was compared to that from argon plasma coagulation (APC) in established ex vivo animal models. Three consecutive patients with complex nonvariceal upper gastrointestinal bleedings were treated and followed up. Results No deep submucosal injury was observed in animal models. The TLS showed a progressive penetration depth with increased power outputs and tissue exposures but very limited vertical tissue injury (0.1 – 2.0 mm) and lateral spreading damage (0.1 – 0.3 mm and 0.2 – 0.7 mm using the 365-µm and 550-µm fibers, respectively). In vivo, endoscopic hemostasis with TLS was always successful without complications. Conclusions The TLS has proven to be very precise and easy to use. This novel technique appears to be a promising tool for advanced interventional endoscopy.