Implantable and wearable measurement system for smart knee prosthesis

In this work we present the implantable and wearable measurement system developed for smart knee prostheses monitoring. The kinematic measurement system contains three anisotropic magnetoresistive sensors embedded into the polyethylene part of the prostheses. The kinematic measurement system also has two inertial measurement units to be worn by the subject on the shank and thigh. Each of this inertial measurement units consisted of a 3D accelerometer and a 3D gyroscope. The force measurement system contains implantable strain gauges that connected in two separate Wheatstone bridges and embedded in a designed capsule-like structure. These systems were validated in a robotic knee simulator against reference force and kinematics systems. The best angle estimator performed with an RMS error of 1.18°±0.25° over four different walking patterns, while the force sensors showed linear behavior in measuring the applied forces, where linear models obtained R²s larger than 0.98.