Selfknotting sutures in Nickel-Titanium: characterization and numerical modeling

A suture is the strand or fiber used by surgeons to sew parts of the living body. This process could be really complicated when deep tissues are involved, since the low mobility and the high risk to damage other delicate structures (e.g. the dura mater, the outer of the cerebral membranes). Nowadays a wide variety of synthetic or natural wires is employed in the clinical practice: it is really important for the surgeon to realize proper suture knots, whose number increases with the decrease of the wire diameter, not too much tight or loose, to have a successful surgery in the shortest timeframe. CNR in Lecco together with the Dott. Dallolio designed a new Nickel-Titanium suture which brings some advantages compared to the commercially available ones. It is a “self-knotting” wire device exploiting the peculiar property of the shape memory effect: a close shape is memorized through specific heat treatments; once implanted in the open configuration the surgeon does not need to pack any knot since the suture is closing by itself only using some drops of physiological solution. A finite element model of the suture has been implemented and a user subroutine able to simulate the shape memory effect has been adopted to replicate the experimental behavior. The aim is the generation of a digital twin of the device, apt to give a better insight at the state of stress and strain under loading. According to that, an optimization of the device manufacturing and implantation processes is suggested.