Surgery

Candidates. The primary indications for surgery are pain and significant limitations of movement, including walking, that cannot be treated by less invasive therapies. Some experts suggest, however, that joint replacement should be considered earlier rather than as a last resort. They argue that patients who wait until they are severely disabled do not recover as completely as those who have the procedure earlier.

Patients who may not be good candidates are those with the following conditions:

• Severe neurologic, emotional, or mental disorders
• Severe osteoporosis
• Other chronic medical conditions
• Obesity

Surgeons often prefer to delay prosthetic implantation in younger patients, because implants wear out and they will require at least one revision procedure later on. Newer, more long-lasting materials, however, may help reduce the rate of re-operations.

Procedure Description. Although the following is mostly a description of hip replacement surgery, the principles are similar for other arthroplasties.

The surgeon removes the ball and socket joint that joins the pelvis and thigh bone (femur) and replaces it with an artificial joint (a prosthesis). It is composed of two pieces:

• A cup-like device fits in the hip socket (called the acetabula), which has been hollowed out. This ball-and-socket cup is positioned to form the new joint.
• A metal shaft, or stem, with a polished metal ball at the top, is inserted into the narrow center of the femur.

The prosthesis is usually made of a metal alloy and plastic. A ceramic implant may prove to last longer than other materials and be a safe option for younger patients.

There are different options available for attaching it to the adjoining bones:

• A cement made of polymethylmethacrylate (usually preferred for older patients who generally have thinner bones).
• So-called cementless implants, in which the prosthesis is coated with a porous material that allows bone to grow into and eventually adhere to the device. These implants are usually used for patients younger than age 65, who are likely to need repeat surgery in their lifetime.