This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Some Klingon infants had a curvature of the spine, which could be corrected by surgery. This "defect" tended to run in Klingon families, especially among females. Federation medicine had advanced beyond that, allowing an additional choice of treatment which involved genetic modification. (VOY: "Lineage")
Some species had more than one spinal column. The Yallitians from the Delta Quadrant had three spinal columns, (VOY: "Phage") and the Talaxians, also from the Delta Quadrant, had two spinal columns. (VOY: "Scientific Method")
In 3189, an atomic scan of Philippa Georgiou's musculoskeletal system revealed she had a bone mineral content (BMC) of 55.2 grams (g) and an areal bone mineral density (aBMD) of 1.01 grams per square centimeters (g/cm2) in her spine. (DIS: "The Sanctuary")