A Novel Bio-Microelectromechanical System for In Vivo Diagnostic Monitoring of Fracture Healing

The ability to detect a normal from aberrant bone healing cascade during the acute fracture fixation period (1–3 weeks post trauma) is critically important to insure a favorable clinical outcome for many complex fracture cases. Radiographic evaluations do not have the inherent fidelity to make qualitative predictions during the acute healing phase. Early detection of an atypical healing profile would allow for revision strategies to be employed without the need for expensive and undesirable follow-up surgeries. In an effort to address the critical need to diagnose the course of bone fracture healing in the vitally important early healing phase, our research group has developed a radio frequency (RF) strain sensor that takes advantages of the recent advances in meta-materials and micro-electo-mechanical systems (MEMS) technology. Our MEMS sensor is biocompatible (bioMEMS), inductively powered and monitors the surface strains on implanted hardware [1, 2]. Another novel feature of this new sensor is that it does not require an internal-external physical connection to sense and transmit in vivo biological data. The essence of the sensor’s design is that straining the integrated RF bioMEMS circuit results in a shift in its resonant frequency (ResF). Through telemetric detection of this ResF shift, it is possible to longitudinally monitor the temporal changes in hardware strain. It is well understood that that as proper fracture healing progresses (i.e. increasingly stable tissue(s) stabilizing the fracture sight) that the load/strain born by orthopaedic implant diminishes. Therefore, telemetric measurements of our bioMEMS system (i.e. hardware load/strain) provide direct insight into the degree of fracture stabilization and healing.