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Severe valgus deformity is manageable with soft tissue release, constrained condylar implant
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Severe valgus knee deformity can be challenging to manage in patients undergoing total knee arthroplasty, but it can be addressed through gap balancing and other techniques, according to a knee surgeon.
“The valgus deformity often comes about primarily because there is lateral bone loss on the femur,” Steven B. Haas, MD, said. “The femoral condylar laterally is eroded. The tibia erodes away eventually, as well, so in the bad deformities you have tibial erosion, too. The lateral soft tissues are tight and the medial soft tissues may be elongated.”
When correcting severe valgus deformity, the tibia should be cut at 90°. The femur should be cut at 3° to 5° prior to balancing the soft tissue, which is initially done in extension, he noted.
Altered rotational landmarks
Rotational alignment is essential, but difficult to obtain in patients with severe valgus deformity. Therefore, Haas suggested using the anteroposterior axis (Whiteside’s line) or the epicondylar axis as a rotational landmark in more severe cases.
When the knee is rotated, a good technique Haas recommended is to pin the medial side of the knee to avoid taking more medial bone.
“You just want to compensate for the deficient lateral bone,” he said noting a gap balancing technique could be done.
In moderate to severe valgus knee deformities, Haas said the tibia should be cut less to avoid creating a huge gap to “compensate for the attenuated [medial collateral ligament] MCL” that can occur after the lateral release.
“If it passively corrects, this is usually because you have erosion on the femur and tibia and the ligaments are not stretched out, and little lateral releasing is going to need to be done,” Haas said. “Sometimes a more minor release [is needed], but not usually a lot. If it does not passively correct, this is when you are going to have to do more releases.”
Soft tissue release
In terms of soft tissue releases, the goal is rectangular flexion and extension gaps. Haas noted any tight structures on the lateral side should be released. He said the pie crust release technique can be used on the iliotibial band in cases of normal deformities, but surgeons may need to extend that to the posterolateral arcuate complex in patients with moderate or more severe deformities.
Research has suggested that an inside-out soft tissue release be done for severe knee deformity using a bovie to release the posterolateral capsule and posterolateral corner. For severe deformities and deformities with an incompetent MCL due to stretching, surgeons should use a constrained condylar prosthesis, Haas said.
“A constrained condylar knee has the advantage of not over-lengthening the knee because sometimes, if you are left with doing so much releasing, especially in an elderly patient, you are going to elongate the leg, which could be a problem. Additionally, you can get into stretching the peroneal nerve, which is a problem because of the foot drop [that can occur],” he said. – by Casey Tingle
- Reference:
- Haas SB. Paper #79. Presented at: Current Concepts in Joint Replacement Winter Meeting. Dec. 13-16, 2016; Orlando, Fla.
- For more information:
- Steven B. Haas, MD, can be reached at Hospital for Special Surgery, 535 E. 70th St., New York, NY 10021; email: haass@hss.edu.
Disclosure: Haas reports he is on the medical advisory board for APOS Medical & Sports Technologies Ltd.; has ownership for design, development at Sandance Technology/Ortosecure; and receives royalties and research support from and is a consultant for Smith & Nephew.