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Diagnosis for a Total Hip Replacement

Orthopedic Surgery

When does someone need a revision total hip replacement?

Implant wear or 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.

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.

In addition, patients who are younger when they undergo the initial hip replacement may "outlive" the life expectancy of their artificial hip. For these patients, there is a higher long-term risk that revision surgery will be needed due to loosening or wear.

In some cases, tiny particles that wear off the cup's plastic liner accumulate around the hip joint and are attacked by the body's immune system. This immune response also attacks the healthy bone around the implant, leading to a condition called osteolysis. In osteolysis, the bone around the implant deteriorates, making the implant loose or unstable.

Fortunately, plastics have improved greatly over the years, so plastic wear and osteolysis occur less frequently today than they did with earlier generations of implants.

Infection

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 prosthetic hip. 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.

When the infection has been cleared, your doctor will perform a second surgery to remove the antibiotic spacer and insert a new prosthesis. In general, removing the implant leads to a higher chance of curing the infection, but is associated with a longer recovery.

In some cases, your doctor may be able to remove the implants, wash out the hip, and place a new prosthesis all in the same operation. This procedure, which is called a one- stage exchange, may be appropriate in limited situations.

Recurrent Dislocation

A hip replacement has a ball-and-socket structure like that of your natural hip. For a hip replacement to work well, the ball must remain inside the socket. Trauma or certain hip positions can sometimes cause the ball to become dislodged from the socket. This is called a "hip dislocation." If you experience recurrent hip dislocations, you may need revision surgery to better align your hip joint or to insert a special implant designed to prevent dislocations.

Fracture

A periprosthetic fracture is a broken bone that occurs around an implant. These fractures are most often the result of a fall, and often require revision surgery. To determine whether a revision is needed, your doctor will consider several factors, including the amount of remaining bone, whether your implant is loose, and the location of the fracture.

In rare circumstances, an implant itself can break. This also requires revision surgery.

Reaction to Metal Ions and Allergy to Metal

Over time, the metals used in implants can break down or wear, causing tiny particles to fall off the device into the space around the implant. This is more common with "metal- on-metal" devices, in which both the ball and socket components are made of metal. In some patients, sensitivity to the metal ions in these particles can result in damage to the bone and soft tissues around the hip and lead to the need for revision surgery.

In very rare cases, a patient allergy to the metal used in implants may cause pain around the site of the implant. There is no definitive agreement among doctors regarding metal allergy in this setting, however, and more studies are needed.

Other Factors

The likelihood of needing revision hip replacement is also impacted by individual differences among patients. For example, patients who are younger and more active are more likely to experience issues related to implant wear. Patients who have certain medical conditions, such as obesity or diabetes, and those who have had certain surgical procedures in the past, are more likely to experience infection or implant failure.