There are two main types of hip replacement operation, but a number of different components and surgical techniques may be used.
Total hip replacement
In a total hip replacement, part of the thigh bone (femur) including the ball (head of femur) is removed and a new, smaller artificial ball is fixed into the rest of the thigh bone. The surface of the existing socket in the pelvis (the acetabulum) is roughened to accept a new socket component that will join up (articulate) with the new ball component.
Many artificial joint components are fixed into the bone with acrylic cement. However, it’s becoming more common, especially in younger, more active patients, for one part (usually the socket) or both parts to be inserted without cement. If cement isn’t used, the surfaces of the implants are roughened or specially treated to encourage bone to grow onto them. Bone is a living substance and, as long as it’s strong and healthy, it’ll continue to renew itself over time and provide a long-lasting bond. Where only one part is fixed with cement, it’s known as a hybrid hip replacement.
The replacement parts can be plastic (polyethylene), metal or ceramic and are used in different combinations:
- Metal-on-plastic (a metal ball with a plastic socket) is the most widely used combination.
- Ceramic-on-plastic (a ceramic ball with a plastic socket) or ceramic-on-ceramic (where both parts are ceramic) are often used in younger, more active patients.
- Ceramic-on-ceramic (aceramic ball with a ceramic socket) is very occasionally used in younger, more active patients.
When this occurs, your doctor may recommend that you have a second operation to remove some or all of the parts of the original prosthesis and replace them with new ones. This procedure is called revision total hip replacement.
Although both procedures have the same goals—to relieve pain and improve function and quality of life—revision surgery is different than primary total hip replacement. Revision hip replacement is a longer, more complex procedure. It requires extensive planning, as well as the use of specialized implants and tools, in order to achieve a good result.
When Revision Total Hip Replacement Is Recommended
Implant Wear and Loosening
In order for a total hip replacement to function properly, an implant must remain firmly attached to the bone. During the initial surgery, the hip replacement components were either cemented into place or were “press fit” into the bone to allow bone to grow onto them. Sometimes, however, bone may fail to grow onto press-fit components. In addition, cemented or press-fit components that were once firmly fixed to the bone can eventually loosen, resulting in a painful hip.
Wear of the plastic liner (red arrow) and osteolysis (yellow arrow) have caused the acetabular cup to loosen. The femoral head (ball) is no longer centered in the cup.The cause of loosening is not always clear, but repetitive high-impact activities, excessive body weight, and wear of the plastic liner between the ball and the metal cup are all factors that may contribute.
Infection is a potential complication of any surgical procedure, including total hip replacement. Infection occurs when bacteria attach in and around the surface of the prosthesis. Infection may occur while you are in the hospital or after you go home. It may even occur years later.
If a total hip replacement becomes infected, it can be painful and the implant may begin to lose its attachment to the bone. Even if the implant remains properly fixed to the bone, there may still be pain, instability, and drainage from the infection. Because bacteria cannot be easily eliminated from a joint replacement with antibiotics alone, revision surgery is usually necessary.
Revision surgery for infection can be done in different ways. To determine which procedure is best for you, your doctor will consider a number of factors, including:
- The type of bacteria
- The duration and severity of the infection
- Your preference for a specific treatment
Debridement. In this procedure, your doctor will open up your hip, wash out the bacteria, and exchange the ball and plastic liner. The metal implants that are firmly attached to the bone are left in place. After debridement, you will receive intravenous antibiotics for several weeks to help cure the infection.
Staged surgery. In some cases, the implants must be completely removed. If the implants are removed to treat the infection, your doctor will usually perform the revision in two separate surgeries.
In the first surgery, your doctor will remove the implants and place a temporary cement spacer in your hip. This spacer is treated with antibiotics to help fight the infection and will remain in your hip for several weeks. During this time, you will also receive intravenous antibiotics.