Treatment for scoliosis. Coloured X-ray of the torso of a 28 year old with a Harrington rod in place to treat scoliosis. Scoliosis is a lateral (sideways) curvature of the spine that usually starts in infancy or adolescence, and is most often seen in girls. The Harrington rod is a metal rod that attaches to the spine at the top and bottom of the curve and uses a ratcheting mechanism to stretch and straighten the spine. The cause of scoliosis is not known, although occasionally it may be due to a congenital abnormality of the vertebrae (blocks that make up the spine), polio or an injury.