Scoliosis uses the 45 to 50° threshold as a result of the well-documented, plus or minus 5° measurement error that can occur while measuring Cobb angles. Surgeons who are specialized in spine surgery perform surgery for scoliosis. To completely straighten a scoliotic spine is usually impossible, but for the most part, significant corrections are achieved. The two main types of surgery are: One or both of these surgical procedures may be needed. The surgery may be done in one or two stages and, on average, takes four to eight hours. A 50-year follow-up study published in the "Journal of the American
Supernumerary body part two or more different populations of genetically distinct cells that originated in different zygotes that have merged; anatomical structures are typically mixed depending on which cells are prevalent in different body parts, for example plants can have two different types of flowers. A mosaic is a genetic anomaly similar in nature and effects to a chimera: genetically different populations of cells within one organism, originated from some propagated mutation of a single cell rather than from outside sources. In Hindu mythology, additional limbs and heads are considered a sign of power. In Greek mythology, Artemis, the goddess of fertility, was