Keys to a Successful Revision TKA
Revision total knee arthroplasty (TKA) is a technically demanding procedure, but it can be done quite successfully with the right preparation and a methodical approach.
That’s the takeaway message from a lecture presented by Steven B. Haas, MD, at ICJR’s Revision Hip & Knee Course. Dr. Haas is Chief of Knee Service, Hospital for Special Surgery, New York, New York.
The good news, Dr. Haas noted, is that more than 95% of primary TKAs are successful, providing patients with excellent pain relief and good range of motion.
But over time, some patients will need a revision procedure. And as the number of primary TKAs grows over the next 2 decades, the demand for revision procedures will increase as well.
Diagnosis and Planning
When a patient presents with pain following a TKA, the first thought should not be, “Let’s do a revision.” Diagnosing the source of the pain is crucial – revising a painful TKA without knowing why the patient is experiencing pain is a recipe for a poor outcomes.
Once the diagnosis is known and revision is appropriate, the surgeon should follow a step-by-step preoperative planning process. That means knowing as much as possible about what will need to be done during the procedure and preparing for the expected – and, more importantly, the unexpected.
The surgeons should carefully evaluate the preoperative X-rays to determine:
Equipment needs, such as osteotomes, saw blades, metal cutting bits, femoral and tibial extraction tools, antibiotic cement, allograft material, and appropriate implants
- Component removal
- Gap balancing
- Reconstruction of bone defects
The procedure will be a lot easier, Dr. Haas said, if the surgeon thinks about it and plans ahead of time.
Some TKA components are easier to remove than others, and the surgeon should know the type of implant the patient has to adequately prepare for the removal. The key, Dr. Haas said, is for the surgeon to take his or her time with disrupting the prosthesis/cement and prosthesis/bone interface and to avoid trying to remove the component before it is loose.
His recommended order of component removal is:
- Tibial insert
Dr. Haas prefers to remove the femur before the tibia to keep debris out of the tibial intramedullary canal. It is also easier, he said, to remove the tibia if the femur is not in the way.
The patella should be removed last, he said, to minimize the risk of fracturing this fragile bone.
Sizing and Gaps
This is probably the most important part of the TKA revision, Dr. Haas said. It is important to ensure the new implant is approximately the same size as the old implant (unless the knee is being revised for stiffness), as the size of the implant sets the flexion gap. The surgeon can augment posteriorly as necessary, and then augment distally to allow the extension gap to match the flexion gap.
Using an implant that is too small is a common error, Dr. Haas said. When the implant is too small, the flexion gap increases, which forces the surgeon to increase the extension gap. This results in raising the joint line.
Dr. Haas offered these general rules for gap evaluation:
- Establish the flexion gap and then build up the extension gap to mate it.
- Remember that tibial changes affect flexion and extension equally.
- The femoral AP size changes after flexion.
- Distal femur dimensional changes affect extension.
Click the image above to watch Dr. Haas’s presentation, with more tips for a successful revision TKA.