Osteotomy literally means cutting of the bone. In orthopaedic surgery, an osteotomy is an operation where a section of the bone is cut so that the bone may be realigned to a better position. An osteotomy can change the angle or the rotation of a bone which, in turn, can affect the function of a nearby joint.
In the hip, this is done to relieve pressure on the arthritic surface of a joint. The two most common indications for osteotomy of the hip are osteoarthritis and avascular necrosis. The goal is to transfer weight bearing from an area of diseased cartilage to an area of normal cartilage.
By making a cut in the proximal femur just below the joint, the joint surface or articular surface of the femoral head can be rotated so that normal cartilage is placed in the position of greatest stress. While this will not cure the underlying arthritis or avascular necrosis, it may buy time in a younger patient and delay the need for hip replacement surgery.
An operation that increases the angle of the hip is called a valgus osteotomy; an operation that decreases the angle of the hip is called a varus osteotomy.
Sometimes the hip joint socket or acetabulum is too shallow and there is no covering over part of the femoral head. In this case, a cut through the bone of the pelvis or pelvic osteotomy may be done to slide bone over the uncovered femoral head.
As part of an osteotomy, bone may be removed or bone graft may be added to the femur. In rare circumstances, both pelvic and femoral osteotomies may be done if there are deformities on both sides of the hip joint.
The surgeon will take measurements from preoperative x-rays and CT scan to determine the exact angle of the cut. He will try to rotate the bone so that the normal articular surface is placed in a position of com-fort for the patient. An osteotomy requires some form of internal fixation such as plates and screws to hold the two parts of the bone together while healing takes place. Most often there will be a period of limited or protected weight bearing after surgery.
As noted, an osteotomy is a procedure to buy time in a younger patient who wants to preserve his or her natural hip for as long as possible. Most surgeons recognize, however, that a total hip replacement may be necessary years down the line. For this reason, care is taken to make sure that the hip is aligned in a way that does not interfere with placement of total hip components.