Active Implant System Based on SMA Actuators for Improved Bone Fracture Healing

Abstract Shape memory alloys (SMAs) are an attractive technology in actuators and sensors because of their versatile geometry, low weight, high energy density, and low cost. Recent scientific research found that a switchable stiffness of an implant for bone fracture treatment with individual stimulation patterns to be applied to the fracture site may improve the patient’s healing process. The first intelligent implant system was developed and realized. This active implant system consists of two actuation mechanisms. The first SMA actuator system generates a switching capability between rigid and soft states in cooperation with an incompressible element. A second set of SMA actuators generates controlled stimulation of the fracture site in the soft implant state by contracting and restoring with an adaptable stroke. This work first introduces the mechanism of the active implant with a short overview of the mechanical parts. Next, the novel batterie-driven electronic control unit is presented with its realized miniaturized PCB, and the user interface is introduced, enabling wireless control and monitoring via the internet. Following the manual measuring setup, the demonstration case is presented, which is also equipped with an electronic control unit and the terminal where the user interface allows the control of the implant.