About Revision Total Knee Replacements
The majority of knee replacements do very well, but there are some that fail, either through problems such as infection or malalignment, or because they wear out and work loose. It is usually the polyethylene component that wears out, although more modern polyethylene components have a much lower rate of wear than older ones. Rarely a fracture around the knee may need a revision operation.
In a revision knee replacement, the old components are removed and new ones are inserted. In the case of infection, this may need to be as a two-stage procedure, where a temporary implant is inserted for a few months while the infection is treated, before the definitive new knee replacement is inserted at the second stage. This is clearly a major operation and there are risks associated with it. Although the risks detailed below are a general guide, revision knee surgery has a somewhat less predictable outcome than a standard knee replacement, and these risks will be discussed with you before your surgery.
Outcomes of Revision Total Knee Replacement
All of my joint replacement patients are invited to participate in the National Joint Registry which monitors outcomes of hip and knee replacement. Using this national data, we can predict that approximately 85% of revision total knee replacements are still functioning well after 10 years. Loosening or early failure of the revision total knee replacement is rare, although more common in those knees revised for infection. If this were to occur then the knee may require further surgery.
Complications of Revision Total Knee Replacement
All operations come with attached risks. These can include:
Bleeding – a blood transfusion may be required but this is rare.
Infection – This is a potentially devastating complication and all efforts are taken to prevent this. These include the use of antiseptic skin preparations during surgery, ultra-clean air laminar flow operating theatres with every care taken to maintain sterility during surgery, and the use of antibiotics during and after surgery. Despite this infections can still occur. These may be superficial wound infections which can be successfully treated with antibiotics, but a severe deep infection is likely to need further surgery to wash out the knee, or even to remove and replace the components. The risk of a deep infection is less than 1%, although this is likely to be higher in patients who are having a revision for infection.
Blood clots – a blood clot in the leg (a deep vein thrombosis; DVT) or in the lung (a pulmonary embolus; PE) is a potentially serious complication. The risk is decreased by giving you blood thinning medication for 14 days following surgery. The most important factor to reduce this risk is getting you mobile as quickly as possible. The risk of a DVT that causes symptoms is approximately 3%; the risk of a PE is 1%. If you are unfortunate enough to develop either of these, then blood thinning medication such as warfarin is usually required for 3-6 months.
Knee stiffness – Although uncommon following revision knee replacement, the knee may become stiff following surgery. Manipulation of the joint under general anaesthetic to bend the knee and break down scar tissue within the joint may be required. The risk of this is less than 1%; although this may be higher in knees that are revised primarily for stiffness.
Numbness – it is common to have some numbness over the outside of the knee. This is because the small skin nerves running across the knee are cut at the time of surgery. This numbness does not usually cause problems.
Wear – Modern knee prostheses mean that your revision joint replacement should last many years. The plastic bearing can wear out, and if the metal components are well fixed, the bearing can be replaced.
Revision – Revision TKRs have a low rate of revision and the majority of patients with them do well. However, should the revision knee wear out or become loose, then it may be necessary to remove and replace the components once again.