Integration of a telemetric system within an intramedullary nail for monitoring of the fracture healing progress

This contribution presents a system designed to monitor the fracture healing progress after osteosynthesis of the femoral bone, using an intramedullary nail. The instrumented nail enables the surgeon to perform stiffness measurements of the bone/implant system in vivo. Various techniques have been developed in the past to measure the stiffness of the callus, but little research has been done on fractures treated with nails. The presented system consists of a passive measuring module, which is located inside the nail. Power and data are transmitted wirelessly by a low-frequent inductive link between the passive module and a reader unit located outside the body. The conductive material of the implant and the distance between implant and reader unit make the design of this telemetric system ambitious.