Hip and knee replacement components last a long time, but do not always last forever. Despite successful primary surgery, some people ultimately require revision surgery, where some or all of the prosthetic components are exchanged. Revision joint replacement surgery is when some or all of the existing joint replacement implants are removed and new ones are implanted. A minor revision is when modular components that are fixed to other implants rather than to the bone are exchanged. A major revision is when implants that are fixed to bone are exchanged. Sometimes not all of the implants need to be exchanged, even in a major revision. One of my interests is investigating and managing patients who are not satisfied with their total hip or knee joint replacement.
Common reasons for revision joint replacement
Revision joint replacement surgery may be required for a variety of reasons, though the most common reasons are implant wear, deep joint infection, fracture of the bone around the implant (periprosthetic fracture) due to trauma such as a fall, and joint instability. Revision surgery is usually more complicated than the initial joint replacement surgery, but with detailed pre-operative assessment and appropriate post-operative support it can usually be performed safely with risks that are only slightly higher than those for primary joint replacement surgery.
Implant wear
All hip and knee replacement components can wear out with time, although this wear usually occurs over many years – often over decades – and usually does not cause any problems. As wear occurs, however, microscopic wear particles can cause areas of bone loss around the prosthesis, which in some cases can result in the implant becoming loose and causing pain. Revision joint replacement removes the worn joint replacement and replaces it with a new one that is well fixed and comfortable. (see Bearing Surfaces in Joint Replacement)
Deep Joint Infection
Approximately 1% of total hip and knee replacements are complicated by deep joint infection. When managed appropriately soon after the onset of infection a joint replacement may be salvaged by surgery to wash the infection out. Unfortunately, partly because it can be difficult to diagnose, deep joint infection often necessitates the removal of the joint replacement, followed by a period of antibiotics with no joint replacement, and a second operation to reimplant the joint replacement when the infection has been eradicated; often there is a three month period between removal and reimplantation of the joint replacement.
Periprosthetic fracture
A fall onto a hip or knee replacement can cause a fracture of the bone around the joint replacement. This can result in loosening of the implant, even if it was previously functioning completely normally with no problems. If the bone around the implant breaks it is often necessary to perform a revision joint replacement as part of the management of the fracture.
Joint Instability
Revision joint replacement surgery can usually address problems of joint instability. In the hip, this instability is usually manifested as recurrent dislocation. In the knee it usually manifests as a feeling of looseness in the knee, or a feeling that the knee will not adequately support weight without giving way. The best results of revision joint replacement surgery for joint instability are when all of the joint is replaced, even though this usually means a more involved operation; trying to ‘get away’ with only replacing part of the joint is less likely to result in a satisfactory outcome.
Results of revision joint replacement
The results of a successful revision joint replacement are not as good as the results of a successful primary joint replacement. Patient satisfaction is lower overall, and rates of deep joint infection and joint instability are higher than they are for primary joint replacement. Nonetheless, revision joint replacement is largely successful, and a successful revision total joint replacement is much better than a failed primary joint replacement. The Australian National Joint Replacement Registry suggests that almost 80% of revision hip and knee replacements are still functioning after 10 years.
Revision total joint replacement for pain
If a primary total joint replacement is painful, but the reason for the pain cannot be determined, the results of revision total joint replacement are unpredictable. Because of this, I do not usually recommend revision surgery to manage a painful total joint replacement that is not infected and is functioning well otherwise. However, as one of my interests is patient satisfaction following total joint replacement, I am happy to see patients who have a painful but otherwise well functioning joint replacement.