Magnetoelastic Strain Sensor for Optimized Assessment of Bone Fracture Fixation

In orthopedic surgery, measuring the strain in an internal plate over time makes it possible to monitor the bone fracture healing process. Magnetoelastic sensing provides a wireless, highly sensitive, and low-cost technique for measuring strain. An amorphous ribbon is bonded to the implant plate and an emitter/receiver unit is placed outside the patient´s body. Bonding the sensor to a plane surface decreases its output signal intensity due to an increase of the magnetic anisotropy. To overcome this problem, we demonstrate a sensor signal detection system, which increases the signal-to-noise ratio. This system is based on a pair of flat miniaturized coils that can be put on the patient´s skin. This technology is then applied to measure strain in a plate that supports a fractured generic bone under static loading conditions. The sensor output responses are presented and the high accuracy values obtained are given.