Implementation of an implantable joint-angle transducer.

An implantable joint-angle transducer (IJAT) was implemented to provide command-control information from the wrist for functional neuromuscular stimulation (FNS) neuroprostheses. The IJAT uses the Hall effect to sense joint angle. The objectives of this study were to evaluate (1) chronic functionality, (2) safety and biocompatibility, (3) repeatability of the implantation procedure, and (4) clinical feasibility. Accelerated bench testing projected an operating period of over 50 years. In chronic animal experiments, stable output was obtained from three of four IJATs for periods of 10 to 19 months. Histology revealed acceptable osseointegration of the implant. The device has been implanted in human subjects for over 2 years and provides an excellent control signal for hand grasp. We conclude that this device is safe and effective for chronic human use as a control input for an implanted hand neuroprosthesis.