Functional neuromuscular stimulation system

A position monitoring system for providing output signals which vary in proportion to monitored movement relative to two axes, the system comprising:

• a permanent magnet mounted within a ball member;
• a human implantable socket in which said ball member is movably received, said socket including at least three Hall-effect plates defining first and second axes such that movement of the ball member and the socket relative to each other varies a physical proximity of the permanent magnet relative to the at least three Hall-effect plates;
• a human implantable source of electrical potential which is connected to apply an electrical potential across each of the Hall-effect plates in a first direction to establish a magnetic flux in association with each Hall-effect plate;
• a human implantable monitor for monitoring a potential difference across each Hall-effect plate in a direction generally transverse to the first direction, the monitor providing an analog monitor signal which varies in proportion to the potential difference such that as the ball member and socket move relative to each other, the physical proximity of the magnet relative to the Hall-effect plates changes as does the magnetic flux through each Hall-effect plate and the potential thereacross;
• human implantable means for deriving from the analog monitor signals first and second analog output signals which are indicative of the relative position of the ball member and socket along said first and second axes, respectively;
• a human implantable telemetry system for digitally encoding the first and second analog output signals, the telemetry system including:
• a receiving coil for receiving a radio frequency signal from an external radio frequency transmitting coil,
• a power supply operatively connected to said receiving coil for converting radio frequency signal induced currents in said receiving coil into electromotive power,
• an encoding means operatively connected to said deriving means to encode said analog output signals of said deriving means into output data in a preselected data format, and,
• a gate means operatively connected to said encoding means to selectively alter an impedance of said implantable receiving coil in accordance with said output data of said encoding means such that a characteristic of said external transmit coil varies with the altered impedance of said implantable receiving coil;
• and,
• an external portable control system connected to said external transmit coil for selecting stimulation pulse train parameters in response to changes in said characteristic of said external transmit coil.