Implanted devices that pick up motor signals from the brain and pass them to the muscles, offered to Worf as the conventional treatment for paralysis but rejected by him as insufficient.
Neural transducers are the standard 24th-century answer to a severed spinal cord. One set of implants reads the signals the brain sends towards the limbs, and a second set fitted in the muscles receives them, bypassing the damaged section of the spine altogether.
In the Next Generation episode Ethics, Doctor Crusher proposes them to Worf after an accident in a cargo bay leaves him paralysed from the waist down. She explains that with practice he could expect to recover most, though not all, of his mobility.
For Worf that is not enough. He cannot accept lurching through the corridors as an object of pity, tears the devices off after a brief trial, and first asks Riker to help him die by the Hegh'bat ritual, then stakes his life on Doctor Russell's untested genetronic replacement of his entire spinal column.