Although joint replacement surgery has been amazingly successful, approximately ten percent of implants will fail and require a second procedure, called revision, to remove the old implants and replace them with new components.
The decision to perform a revision joint replacement surgery will be based on several factors. The joint may become painful or swollen, due to loosening, wear, or infection. The function of the implant may decline, resulting in a limp, stiffness, or instability. Finally, serial examinations or X-rays may demonstrate a change in the position or condition of the components. All of these factors will determine when joint revision surgery is needed.
The natural history of failed implant surgery is an increase in pain, a change in the position of the implant, or a decrease in the function of the implant with limp or dislocation. Patients who demonstrate these symptoms and signs may require revision joint surgery. Therefore, a standard assessment8 is performed, including a history and physical examination, X-rays, laboratory tests, and possibly aspiration or scintigraphic studies.
The history and physical examination will identify patients who have a change in their pain level. Also, information can be obtained regarding activity levels and use of assistive devices, such as crutches or a cane. Pain of the hip may present as either groin or buttock pain. In addition, pain of the hip can sometimes be perceived of as knee pain, and vice versa. Swelling of the knee can be assessed easily, but swelling of the hip area may be more subtle. Mechanical failure or infection may also present with redness and warmth of the affected joint. A limp or deformity may be identified.
X-rays taken of the area around the joint replacement yield important clues regarding stability of the implant. Failure due to the most common cause, aseptic loosening, can be identified by several findings. For example, the implant may have moved, compared to previous X-rays, or there may be a lucent line between the component and the cement or bone, signifying that the bond between the bone and implant has degraded. Areas of bone loss, or lysis, can be identified. Mechanical failure with broken implants or severe wear is also assessed by comparison to previous X-rays. For these reasons, serial follow-up radiographs are recommended to catch joint failure at an early stage.
Common laboratory tests for possible failed joints include a complete blood count, an erythrocyte sedimentation rate (ESR), and a C-reactive protein test (CRP). These studies are most helpful in the detection of infected joint replacements. The blood count may identify an anemia from chronic disease, and rarely may detect an elevated white blood cell count. The ESR and CRP may be abnormal in the presence of an inflammatory process, such as infection.
Joint fluid may be removed with a needleand analyzed, a technique called aspiration, to give clues as to a possible infection. The knee joint can usually be reached with a needle in Dr. Backe’s office, but the hip more commonly requires a setting that has fluoroscopic X-ray capabilities. In addition, scintigraphic studies that use short-acting radioactive isotopes may be used. Short-acting radioactive isotopes which are injected into the bloodstream may be used. One scintigraphic study, the Technetium99 bone scan, can detect abnormal bone activity such as infection, fracture, or irritation from prosthetic motion. Another study, the Indium111 scan, may be used to detect infection. All of these methods can be used when the natural history of joint replacement changes and revision becomes a possibility.
Benefits and Limits
Revision joint surgery, as previously stated, can be a major procedure that requires complex techniques. It can also have a higher complication rate than primary surgery. In addition, some patients are not medically able to tolerate a long and difficult surgical procedure.
Because of this, nonoperative treatment options are sometimes considered as a first step in the treatment of a failed implant. Obviously, problems that would damage remaining bone quality or make later treatment difficult would eliminate the nonsurgical options. Also, patients treated nonsurgically must realize that they may have significant limits on their function and activity.
Pain that is caused by a failed joint replacement may initially be treated with an increase in pain medications. These treatments may be limited by side effects, such as gastrointestinal upset and ulcers, drowsiness, and constipation. Increased reliance on assistive devices, such as a cane, crutches, or a walker, may be used to postpone revision. Likewise, a brace may decrease episodes of instability or dislocation. These techniques may be cumbersome and a burden to the patient, however. Modification and restriction of activity itself can be used to decrease symptoms. The less active a patient is, the less likely they are to be symptomatic. Finally, some infected joint replacements are treated with suppressive antibiotics to control the infection symptoms. This approach has a variable success rate and would not be expected to eradicate the infection.
Knee revision surgery entails consideration of the femur (thigh bone), tibia (shin bone), and patella (kneecap) components.
Bone stock deficiencies are classified according to several grading systems, and lysis, fracture, or stress shielding can lead to bone loss.
The failed components are removed by a combination of surgical methods and specialized instruments. Reconstruction may require implants with extensions to reach better-quality bone and that effectively replace lost ligament stability.
Ground-up or bulk bone graft may be used.
An implant is fixed in place through cemented or bone in-growth techniques.