Revision Knee Replacement
What is it?
While total knee replacement usually provides long-lasting comfort and function for patients with knee arthritis, infrequently problems can arise. Whenever a knee joint replacement fails to work well, a thorough investigation is needed to establish the nature of the problem and the possible approaches to remedy the situation. Some of the recognized causes of knee arthroplasty failure include weakness, instability, loosening, malalignment, and infection. When I meet someone with a failed knee replacement, I gather all the possible information about the original diagnosis and the surgery – a copy of the operative note and the past x-rays are most helpful. I conduct a thorough physical examination and take special x-rays and other imaging tools to further assess the problem. Other tests, such as blood work and an aspiration of joint fluid for laboratory analysis may shed further light on the problem. Sometimes non-operative management, such as exercises or bracing, can be helpful. Not infrequently, however, a revision surgery may be necessary to address the problem. The type of revision surgery depends on the nature of the problem.
Revision for infection
- Revision for infection is complicated. The vast majority of the time, a “two stage” revision is required- meaning two surgeries are needed. The primary knee needs to be removed, cement with antibiotics is placed to allow the infection to clear for about 3 months, and then a new knee is replaced.
Revision for loosening
- The knee can “loosen” between the cement mantle and the bone. This may be a difficult diagnosis to make. Generally we need to compare x-rays obtained over time to see a change in the position of the implant and a loss of bone. Once this diagnosis is made, and we are certain there is no infection, we can proceed with a revision of the total knee.
Revision for malalignment
- Occasionally the total knee in place is not in proper alignment and a revision may relieve pain. Revision for malalignment can be unpredictable in terms of how much ther surgery is expected to improve patient symptoms.
Revision for fracture
- A fracture around a total knee prosthesis may be fixed with a plate, a rod or a whole new knee prosthesis.
How is it performed?
A revision knee replacement can typically be performed through a similar incision as the original knee replacement. The incision itself may be longer since increased exposure is typically needed. Sometimes, if the old knee was relatively stiff, additional soft tissue releases may need to be performed in the knee to adequately perform the surgery. This may alter some of the early post-operative rehabilitation to allow this to heal appropriately. Sometimes, more than one surgery is needed in order to have a functional knee. This is particularly true when the knee has to be revised for infection
What are the risks?
The surgical risks of revision knee replacement surgery are similar to primary knee replacement surgery. However, in general, the overall risk of complications is greater since there is increased scar in the knee, worse soft tissue quality, and worse bone quality. Here are some of the risks of surgery which as greater than the risk after primary knee replacement surgery:
- Extensor mechanism rupture
- Blood Clots
- Blood loss
- Persistent pain
- Persistent limp
What is the difference between an primary and a revision knee replacement
In principle, the process of performing a revision knee replacement is similar to a primary replacement. However, since there is less bone to work with and the status of the stabilizing ligaments of the knee can be compromised, there are differences in the design. Most revision knee replacements need to be secured to the bone using a stem. Additionally, there is often a stabilizing post or hinge in the center of the knee to make up for deficient knee ligaments. The x-ray to the right demonstrates some of these differences.
What is the recovery like?
Recovery from revision surgery is generally longer and more difficult than in primary knee surgery. Exact timelines for recovery are difficult to know for certain since there is a lot of variability in the reasons for revision surgery and type of revision that needs to be performed. It is our goal to get each patient back to their optimal function as quickly as possible. If revision surgery is performed on the right person, for the right reasons, acceptable long term function of the knee can be achieved.
Who is a good candidate for revision surgery
- We try to optimize all of our patients for surgery.
- At times, the timing of surgery is more urgent, such as in cases of infection or fracture.
- Most of the time we would like to take the time to optimize your health prior to revision surgery.
- Additionally, it is important that your surgeon has a good understanding for why the prior replacement is not functioning very well. If it is not clear why the prior implant is not functioning very well, then the success of revision surgery is unpredictable.
Who is not a good candidate for a revision knee replacement?
The following conditions are known to be associated with worse outcomes after revision surgery.
- Patients with severe spinal problems
- Patients on chronic pain medications
- Patients who actively smoke.
- Patients in poor general health and physical conditioning
- Patients with a BMI > 40
- Patients with severe edema
While having any of these conditions does not mean that a revision total knee arthroplasty cannot be performed, it could mean that alternative methods of treatment may be safer and more predictable.