Despite very good results in terms of function and longevity being currently achieved with primary total knee replacement surgery, knee replacements unfortunately do not last forever. Knee replacement implants may fail after 10 to 15 years. There are many reasons why a revision knee replacement may need to be undertaken. These include
- Wear of the plastic tibial insert
- Deep infection – presenting as persistent pain and swelling
- Loosening of implants – sometimes the bond between the implants and the bone weakens
- Bone loss – plastic wear particles in the knee can cause bone loss or osteolysis
- Malalignment – very rarely a knee can be painful and stiff due to imperfect positioning of the implants
Pre and post-operative x-rays of a revision TKR for worn out plastic tibial insert
Before determining whether a knee replacement needs to be revised many investigations will probably be required. These will include sets of x-rays, blood tests to exclude infection, nuclear bone scanning to detect for early loosening and possible needle aspiration of knee fluid for microbiological examination.
The surgery involves removing all of the previous knee replacement and implanting new components. One problem this can cause is further bone loss and every step is undertaken to minimise this. If infection can be excluded then the revision operation can be carried out in one stage. However if infection is either proven or strongly suspected then the surgery will involve two stages – the first being complete removal of the implants with insertion of an antibiotic spacer and the second being the insertion of the new knee implants some 6-8 weeks later. In the interim period the patient may require the intravenous administration of antibiotic to fully eradicate the infection.
Revision knee replacement is more complex and demanding than primary surgery but is still a viable option for a ‘worn out’ knee replacement. The operating time is slightly longer as is the duration of the hospital stay – this could be over 1 week rather than the 3 to 6 days for primary total knee replacement (TKR). During surgery the new prosthesis has to be able to cope with the bone loss caused by the removal of the original knee replacement and this is achieved by using stems inserted into both the femur and tibia and metal blocks and wedges which are attached to the main components. The stems provide much improved stability to the construct.
Revision TKR is a major operation but can offer excellent pain relief after a failed primary TKR and there are currently very sophisticated implants available to recreate a knee joint with good motion and stability. Following the surgery a demanding rehabilitation regime is undertaken and it can take many months before the true benefit of surgery becomes apparent. Occasionally a knee brace may be required and the range of movement may not be as good as a primary TKR.
All of the risks associated with primary TKR are increased with revision surgery especially infection, bleeding, blood clot formation and nerve damage. Mr Rees specialises in revision TKR and he would be very happy to discuss the merits and possible complications of revision surgery in any patient with continuing problems after a primary TKR.
