Electromagnetic Induction Heating of an Orthopaedic Nickel-Titanium Shape Memory Device

Shape memory orthopaedic implants made from nickel titanium (NiTi) might allow the modulation of fracture healing, changing their cross sectional shape by employing the shape memory effect We aimed to show the feasibility and safety of contact free electromagnetic induction heating of NiTi implants in a rat model A water cooled generator oscillator combination was used Induction characteristics were determined by measuring the temperature increase of a test sample in correlation to generator power and time In 53 rats NiTi implants were introduced into the right hind leg The animals were transferred to the inductor, and the implant was electromagnetically heated to temperatures between 40 and 60 C Blood samples were drawn before and 4 h after the procedure IL 1 IL 4 IL 10, TNF alpha, and IFN gamma were measured Animals were euthanized at 3 weeks Histological specimens from the hind leg and liver were retrieved and examined for inflammatory changes, necrosis and corrosion pits Cytokine measurements and histological specimens showed no significant differences among the groups We concluded that electromagnetic induction heating of orthopedic NiTi implants is feasible and safe in a rat model This is the first step in the development of new orthopedic implants in which stiffness or rigidity can be modified after implantation to optimize bone healing (c) 2010 Orthopaedic Research Society Published by Wiley Periodicals Inc J Orthop Res 28 1671-1676, 2010