Knee replacement revisions
Why change a knee replacement?
Revision or replacement of a total knee replacement (TKA) or partial knee replacement (UKA) is sometimes necessary. There are many reasons why a knee replacement might need to be changed:
- infections
- ligament or patellar instability, meaning that the ligaments around your knee and prosthesis are no longer functioning properly
- a loosening, when the prosthesis no longer stays in the bone
- wear and tear
- fractures
A special case concerns unicompartmental knee replacements (UKA), which require "totalization" and will be replaced with a total knee replacement. Unfortunately, it is not possible to replace a unicompartmental prosthesis. The most frequent (but rare) cause is the development of osteoarthritis in the other compartments of the knee.
What tests are required before a total knee replacement?
Revision knee replacements (TKR or UKR) are complex procedures for which it is essential to anticipate difficulties with preoperative examinations:
- An X-ray and 3D CT-scan to assess bone damage and plan the new prosthesis. In the most complex cases, the scan can be used to design a custom-made implant.
- A knee aspiration can be used to check for a chronic infection of the prosthesis. If it is negative, the replacement may only involve part of the prosthesis, thus reducing the scope of the procedure.
- In some cases, nuclear medicine examinations such as SPECT-CT or FDG-PET may be necessary in case of diagnostic difficulty.
Image of knee prosthesis aspiration taken under fluoroscopy by a radiologist
What happens during the procedure ?
When possible, the surgeon will use the same approach and therefore the same scar, and will favor minimally invasive techniques and those allowing for a faster return to activities. Sometimes, in cases of bone grafting or osteosynthesis, a period of non-weight-bearing on the operated limb is necessary.
The implants will be different, allowing for optimization of the anchoring of the prosthesis in the bone using keels, sleeves or wedges, and often, prostheses with a greater degree of constraint are required (posterior stabilization, rotating hinge).
The procedure is most often performed under general anesthesia and hospitalization requires between 3 and 5 nights to ensure that the pain is well controlled and to treat any possible anemia.
Even in the case of a post-operative period of non-loading, rehabilitation can begin immediately to maintain mobility and work the knee muscles.
Taking preventive anticoagulation for 5 weeks is necessary to prevent the risk of phlebitis.
What are the risks?
Like any surgical procedure, revision total knee replacement (RTKR) carries risks, the rates of which are slightly higher than in a primary prosthesis:
- The most serious, and fortunately least frequent, risk is infection, affecting less than 1% of patients and often requiring further surgery and prolonged antibiotic therapy. The risk is increased by active smoking. It is essential not to take antibiotics post-operatively, especially if you are experiencing problems with wound healing, without your surgeon's approval.
- the risk of injury to the extensor mechanism. This risk is higher than with primary prostheses because the surgery traumatizes the tissues again.
- Post-operative bleeding and the occurrence of a hematoma are sometimes a source of pain, but often resolve on their own without requiring further surgery.
Distal venous thrombosis, or phlebitis, is also a possible postoperative complication; it can be serious when complicated by pulmonary embolism. Early mobilization, walking, and the preventive anticoagulant treatment prescribed postoperatively help to minimize this risk.