Design and fabrication of an injection tool for neuromuscular microstimulators.

The injection of small implants into precisely localized sites within the body is a difficult task usually undertaken by surgeons or interventive radiologists. We have designed, produced and tested a simple tool for implanting BION wireless microstimulators as an outpatient office procedure. The ability of BIONs to elicit a desired muscle contraction depends on their placement near the motor fibers that innervate the muscle fibers, providing both the requirement and a means for achieving accurate placement. The implant is preloaded into the tip of the cannula of a two-piece insertion tool made from non-conductive polymers. Trial stimulation pulses are generated by the implant as the tool is manipulated into the desired position. The implant is released by withdrawing the cannula over the implant, preserving both the relative location of the implant's electrodes with respect to the target and determining its desired axial orientation, which is important for implants containing motion sensors. The BION Insertion Tool has been used for over 30 BION implants in human subjects to date.