A nickel-titanium shape memory alloy plate for contactless inverse dynamization after internal fixation in a sheep tibia fracture model: A pilot study

Background Inverse dynamization has recently been proposed for the treatment of tibia non-unions. Nickel-titanium (NiTi) shape memory alloys (SMAs) may provide an opportunity for contactless non-invasive alteration of the stiffness of an implant after surgery. Objective The aim of this pilot study was to analyze the feasibility of the one way shape memory effect in a large animal as well as the feasibility of our ovine large animal fracture model. Methods A tibia osteotomy was performed in three sheep, followed by NiTi plate osteosynthesis in two cases and standard locking compression plate (LCP) osteosynthesis in one sheep. Contactless induction heating was performed after 3 weeks in order to alter the stiffness of the NiTi plates. Euthanasia was followed by biomechanical analysis after 8 weeks. Results Successful change of configuration through contactless induction heating was shown in both SMA plates by image intensifier control. Although large differences in bending and torsional stiffness were observed between the operated and contralateral tibia, the sheep ambulated almost normally at six weeks post-operative. Conclusion We were able to trigger the one way shape memory effect which non-invasively altered the stiffness of the plate osteosynthesis.