Tips and Techniques for TKA in the Varus Knee
At ICJR’s Winter Hip & Knee Course, Richard W. McCalden, MD, FRCSC, from London Health Sciences Center, London, Ontario, Canada, shared the tried-and-true techniques he relies on for surgical management of total knee arthroplasty in patients with a varus knee deformity.
Clear out the posterior femur.
After making his distal, anterior, and posterior femur cuts; setting the rotation; and preparing the tibia, Dr. McCalden takes a few minutes to ensure that the back of the knee is cleared out. This is an important step, he said, in ensuring good flexion and full extension of the knee.
Use a spacer block to check flexion and extension.
Dr. McCalden finds a spacer block to be more precise than the trial component to assess the balance of the flexion space and determine if the flexion will be adequate and the knee will be straight in extension.
Have a low threshold for doing a medial release.
Releasing the semimembranous fibers is critical, Dr. McCalden said, as it has a big effect on the extension space. Surgeons should release as much as necessary to get the knee balanced.
Go 1 size down on the tibial tray and then lateralize the tibia.
This gives the surgeon room on the medial side of the knee to remove bone, which helps with balancing the medial collateral ligament (MCL).
Check the tibial cut with a drop rod.
There’s no point in balancing the knee if the tibia cut is in valgus or severe varus. Dr. McCalden uses a simple drop rod to check alignment of the cuts, finding it to be accurate and precise.
Remove medial osteophytes.
Dr. McCalden uses a rongeur to remove overhanging bone, leaving a small amount to provide space between the implant and the MCL.
Perform a “reduction osteotomy” of the tibia.
Depending on the amount of varus, Dr. McCalden performs what he calls a “reduction osteotomy,” in which he uses a saw to remodel the proximal tibia. This is more effective, he said, than chasing the superficial MCL distally. Releasing the bone provides more room for the MCL.
Medialize the patellar button.
When resurfacing the patella, Dr. McCalden medializes the patellar button as much as possible then does a lateral facetectomy to remove bone from the most lateral border of the patella. This decompresses the retinaculum, he said, which allows the patella to sit in a much better position.
Check patellar tracking.
Dr. McCalden accepts only a perfectly well-tracking patella. On radiographs, the patella should be precisely aligned with no tilt.
Set final tibial rotation with the tibial component slightly externally rotated.
The tibial component will look malaligned, but as the knee reduces with the quadriceps mechanism, the component will come back into alignment. This helps with extensor mechanism tracking, Dr. McCalden said.
Click the image above to hear more about these tips and techniques, as well as advice from Dr. McCalden for managing the valgus knee.
Dr. McCalden has disclosed that he is a consultant for Smith & Nephew.