The spinal cord was an important part of a living being's nervous system that ran down the spine and transmityed the motor messages from the brain to the rest of the body.
In 2368, Lieutenant Worf severely injured his spinal cord and was partially paralyzed when a cargo container fell on his back. Doctor Toby Russell, a specialist, came aboard to offer assistance. She and Doctor Crusher replaced his spinal cord with a replicated one made using a genetronic replicator. (TNG: "Ethics")
In 2372, Teirna came aboard the USS Voyager with spinal cord trauma, among other injuries. (VOY: "Basics, Part I")
Captain Picard ripped the Borg Queen's metallic spinal cord apart after all her organic substances had been dissolved by plasma coolant in 2373. (Star Trek: First Contact)