A genitronic replicator was a device designed by Doctor Toby Russell in the mid-24th century. Using genitronics, the device could scan a person's DNA and any damaged organs that they had, and then replicate a new, healthy replacement organ.
In 2368, the device was still in its early stages when Lieutenant Worf from the USS Enterprise-D was struck by a falling container and partially paralyzed when the impact broke his spinal cord. Dr. Russel came on board to consult with Doctor Beverly Crusher about potential remedies to the problem, and broached the idea of using the genitronic replicator to give Worf a new spinal cord and give him full mobility in the process. Crusher was oppposed to the use of the device, given its experimental nature. She backed down and allowed the procedure to go forward when Worf made it clear that he would commit suicide before living life in a paralyzed state. Worf nearly died during the course of the operation, but the redundancies found in Klingon anatomy allowed him to survive the surgery and make a full recovery. (TNG episode: "Ethics")
Doctor Simon Tarses would later refine the procedure, by using it in combination with nano-technology. He would use it to help regenerate the damaged portions of Lieutenant Ro Laren's spinal cord when it was severed by Taran'atar's attack. (DS9 novel: Warpath)
In the Delta Quadrant, the Vidiians also developed and used genitronic technology. The Vidiian, Sulan, used a genitronic device to split B'Elanna Torres into two distinct beings - a Klingon female and a human female. (VOY episode: "Faces")