A spine, also known as a vertebral column or backbone was part of the skeletal system that housed the spinal cord.
Worf's spine was broken in 2367 when a cargo container fell on him. Despite opposition from Doctor Beverly Crusher, Worf elected to go through with a genitronic replication surgery pioneered by Toby Russell that gave him a new spine. Worf nearly died on the operating table, but his Klingon biology enabled him to survive the surgery and he returned to duty within a few weeks. (TNG episode: "Ethics")
Doctor Simon Tarses would later adapt Russell's procedure by using nanites and genitronics to repair Captain Ro Laren's spine after an attack by Taran'atar left her spine broken. She also eventually made a full recovery. (DS9 novel: Warpath)