A synaptic inductor was a medical device used during the 22nd century.
Doctor Phlox used such a tool while performing surgery on Porthos in 2152. It came into use after Phlox had stitched the transplanted pituitary gland into place with an autosuture. (ENT: "A Night in Sickbay")
The original prop is a rare prop because it is one with sound although the sound was not used in the episode.