An osteotomy is a surgical operation whereby a bone is cut to shorten, lengthen, or change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is also used to correct a coxa vara, genu valgum, and genu varum. The surgical procedure called an osteotomy for realignment of the hip and knee joint.