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 operation is done under a general anaesthetic.

Two main types of osteotomies are used in the correction of hip dysplasias and deformities to improve alignment/interaction of acetabulum - (socket) - and femoral head (femur head) - (ball), innominate osteotomies and femoral osteotomies. The bones are cut, reshaped or partially removed to realign the load bearing surfaces of the joint.

Adjustments are made to part of the hip-bone. Many operating methods and variations have been developed. They are defined by the type of cut and adjustment made Some acetabular procedures are named after the surgeons who first described them as Salter (R. Salter), Dega (W. Dega), Sutherland (D.H. Sutherland), Chiari (K. Chiari): other names one may encounter are Ludlov, P. Pemberton, and James B. Steele. Some are named after the shape of cut (e.g. Chevron, Wedge) or the way the bones are aligned (Dial=old style rotary dial phone).

Femoral osteotomies, as the name indicates, involves adjustments made to the femur head and/or the femur.

From http://en.wikipedia.org/wiki/Osteotomy