Patients frequently ask, “What exactly is a total hip replacement?” The simplest answer is that it is a replacement of the worn and arthritic surfaces of the hip joint. A total hip replacement replaces the worn parts of the joint by fixing an artificial surface to all parts that contact each other as the hip bends and pivots.
The hip is a ball-and-socket joint, consisting of the femoral head (the “ball”), the acetabulum (the "socket”) and the hip capsule, or tissue that surrounds the joint. A hip replacement removes the ball and resurfaces the socket side. The ball is attached to the rest of the bone by a stem that fits down into the femoral canal.
Usually, these parts are fixed to the bone without cement, depending on friction for initial fit and bony ingrowth for long-term biological fixation. The implant, which is made of some combination of metal, plastic, and/or ceramic, comes in a variety of sizes and is fitted to the bone to provide an artificial surface that causes no pain when the hip is used.
ANTERIOR HIP REPLACEMENT Anterior Hip Replacement offers a faster recovery time with few, if any, mobility restrictions immediately after surgery.
Using a specially-designed surgical table, the surgeon is able to reach and replace the hip joint from the front of the hip with a small incision, as opposed to the side or back of the hip (posterior) with a larger incision. The gluteal muscles, which are the three muscles that attach to the pelvis, make up the buttocks, and femur are the most important muscles for hip function, are left undisturbed and do not require healing. Additionally, dislocation risks can be reduced with this approach and leg length is more accurately controlled.
With the anterior approach to hip replacement, patients typically are allowed to bend their hip freely immediately after surgery and walk with minimal assistance. Patients undergoing the posterior incisions are often required to follow strict precautions that limit the hip motion for the first two months and limit hip flexion to no more than 60 degrees. These patients are also discharged on a walker and face obstacles when trying to sit in a chair or getting in a car.
A newer technique, that has recently emerged, for hip replacement is called hip resurfacing. In this procedure, the socket is replaced similar to a total hip replacement. The femur, however, is covered or “resurfaced” with a hemispherical component. This fits over the head of the femur and spares the bone of the femoral head and the femoral neck. It is fixed to the femur with cement around the femoral head and has a short stem that passes into the femoral neck. Hip resurfacing is an emerging procedure, most commonly performed in younger patients; and is not indicated for most patients with arthritis of the hip. It is too early to assess the long-term success of this procedure. However, early results are promising and may lead to excellent long-term outcomes.
REVISION TOTAL HIP REPLACEMENT
A third type of hip replacement is referred to as a revision total hip. Since it is repeat surgery, a revision is more complex and often requires a special type of implant used for those patients who have had a hip replacement that has failed. The bone is not as strong when an implant is removed and the ligaments and capsule surrounding the hip may be damaged.
A revision prosthesis helps address these problems because the surgeon can use special implants to provide better support for the prosthesis. One of the most common complications of a revision total hip replacement is dislocation, which is when the ball “pops out” of the socket. Your surgeon may use implants, techniques, and postoperative restrictions to reduce this risk. If the bone is badly damaged, some hip replacement surgeries, usually revision total hip replacements, require a bone graft to reconstruct a deficiency in the patient’s bone. This is an unusual circumstance and in most cases will be discussed at the time of your initial office visit. The human-donor bone graft, which is obtained from a bone bank, has been tested for disease using a testing process even more stringent than the testing process for blood. Your surgeon and his assistants will be glad to answer your questions about bone grafting and will review the advantages and disadvantages with you.