Orthopedic fixture-integrated RFID temperature sensor for the monitoring of deep inflammations

Orthopedic implants could be subjected to infections. Conventional diagnostic tools involve X-Rays, MRI, CT imaging or, more commonly, the onset of the patient's pain. Monitoring the health state of a prosthesis from the outside the limb can be accomplished by through-the-body wireless communication link. However, techniques for integrating a wireless sensor into orthopedic implants require a structural modification of the prosthesis. To overcome this limitation, a non-invasive way to augment a prosthesis with wireless monitoring capability is here proposed for the early detection of local tissue infection. The idea can be applied to an orthopedic fixation plate provided with holes, with no changes to its structure. The fixation bar is transformed into an RFID tag by exciting voltage gap into an unused screw hole. The electrical and geometrical parameters of the exciter enable a convenient two-steps tuning mechanism (coarse and fine) to adjust the working frequency. Preliminary simulations predicted a read range of more than 50 cm outside the body that is suited to an early and non-collaborative diagnosis in the emerging Personalized Healthcare.