During surgery, once the hip joint is exposed, the head and neck of the femur are removed. The shaft of the femur is then reamed to accept the metal component consisting of the head, neck, and stem. The acetabulum is then reamed to accept a plastic cup. The ball and socket are then replaced into normal position. Both of these implants can be fastened into the bone with or without special cement.
- Cemented procedure. The cemented procedure utilizes a doughy substance mixed at the time of surgery that is introduced between the artificial component and the bone. This type of fixation in total hips remains the gold standard and is the method of choice for many surgeons. Depending upon their health and bone density, people over the age of 60 will receive this type of joint fixation.
- Noncemented procedure. Despite its common use, not all individuals are candidates for a cemented hip. Studies show that young active adults tend to loosen their artificial components prematurely. The current trend therefore, is to use an artificial joint covered with a material that allows bone tissue to grow into the metal. A tight bond of scar tissue if formed, which anchors the metal to the bone. This is called a cementless total hip replacement.
This type surgery is technically more sensitive, requiring a more exact fit of the metal component to the femur. In this procedure, the surface of the metal is prepared with a small porous roughened coat, which attracts bone in growth. This process is called porous ingrowth or oseointegration.
In general, the artificial joint implants used in the non-cemented procedure are larger than those used with cement but are still proportional to the size of the individual bone. Since their introduction, many different devices using cementless fixation have been used with the hope that these implants will maintain their attachment to bone for a longer period of time.
Other Types Of Hip Replacement Procedures
There are other types of hip replacement procedures:
- Hybrid fixation refers to a procedure in which one component (usually the socket) is inserted without cement, and one component (usually the stem for the ball of the femur) is inserted with cement.
- Hemi-surface replacement for
osteonecrosis. This is one option the surgeon will utilize to minimize tissue reaction. It involves replacing only the diseased part of the joint. A hemi-surface replacement is often recommended for people who have avascular necrosisand have some remaining articular cartilageon the acetabulum. The hemi-surface replacement preserves and maintains bone by providing stress transfer to the femoral neck and upper femur. It can also help avoid inflammatory reaction and joint loosening.
- Surface replacement of the hip. If the surgeon chooses to do a surface replacement procedure, the neck of the femur is preserved rather than amputated as in conventional stem-type total hip replacement. The femoral head is then reshaped and resurfaced with an artificial or prosthetic shell. When this procedure is used, the femur accepts more of the load (as a normal hip does) and thereby preserves bone. Since the resurfaced head is very similar in size to the normal hip, it proves to be more stable and risk of dislocation is greatly minimized.