Approaches to varus and valgus deformity correction vary

Correction of deformity in knee replacement comes down to knowing how to approach the issue from several different angles, according to an orthopedic surgeon from Hospital for Special Surgery in New York.

Russell E. Windsor, MD, shared several technical tips and pearls in the field of deformity correction at the Current Concepts in Joint Replacement 2010 Winter Meeting in Orlando, Fla.

“Deformity correction is one of the more important goals of total knee replacement,” Windsor said. “You have to restore the anatomic alignment … the key to success is to have the balancing of the soft tissues correct. You do the bone work, but equal in the success of the replacement is the soft tissues.”

Windsor noted there are “basically three types” of deformity to deal with: varus, valgus and flexion.

Correcting varus deformity

Varus deformity characteristics include medial joint space narrowing, with medial joint erosion potentially occurring in a normal medial collateral ligament (MCL), according to Windsor. The goal of correction should be “a rectangular space of both flexion and extension,” he added, noting that bone resection and realignment may be sufficient with small deformities (10° to 15°) but greater deformities could require a release to equalize the flexion gap.

“Generally speaking the most accepted release is a medial superficial MCL release distal off of the tibia,” Windsor said. “I like to do what is called a ‘strip and stretch’ with the laminar spreader. This maintains the femoral condylar axis.”

Medial release typically involves removal of the medial, tibial and femoral osteophytes, followed by a distal release of the superficial MCL from the tibia.

“In the minimally invasive approaches where you do not directly see that distal insertion — which we used to be able to do in the larger incisions — you have to do this somewhat blindly,” Windsor said, adding that he likes to use a straight osteotome to slide along the medial side of the tibia and then utilize laminar spreaders to view the restoration of the rectangular space.

Constraint may be needed in more severe varus releases, and for this, surgeons can use a more constrained, unlinked construct. This avoids leg lengthening and gives the patient an “excellent” combination of deformity relief and good, relatively pain-free function.

Correcting valgus deformity

Valgus deformities are characterized by a contracted or tight lateral collateral ligament (LCL), iliotibial band, popliteus muscle and arcuate ligament complex. The goal of correction, Windsor said, is to “try and achieve 0° to 5°.”

“Some people will want it to be corrected to 0°, others will accept 5°. Just to keep it relatively anatomic,” he noted, adding that correction could also be necessary with an external rotation deformity frequently seen in severe valgus malalignment issues. Furthermore, erosion of bone in the lateral femoral condyle must be taken into account while trying to reproduce the epicondylar axis.

A passively correctable valgus deformity could be handled by restoring the epicondylar axis without lateral release. Formal releases are usually necessary, and Windsor reported there is a controversy regarding which release should be performed first.

“Generally speaking … the popliteus can be released off the femur, the iliotibial band can be step-cut or released distally off of Gerdy’s tubercle, you can do a formal LCL release off the femur and then a differential release of the arcuate ligament complex,” he said.

For mild valgus deformities, Windsor said he releases the popliteus and “maybe the iliotibial band” distally off of the tibia, noting this is usually sufficient. For moderate valgus of 15° to 45°, he starts with the iliotibial bands either step-cut or distal off of Gerdy’s tubercle, then the posterolateral corner of the arcuate ligament, then the LCL. He added that with bigger releases, the popliteus should be preserved to avoid a “significant gapping” in the lateral side inflection.

“In general, release what is tight,” Windsor said. “Release may vary depending on the tightness of all the soft tissues and bone deformity.” – by Robert Press

Reference:

• Windsor RE. Correction of deformity: When the implant itself is not enough. Paper #85. Presented at the Current Concepts in Joint Replacement 2010 Winter Meeting. December 8-11, 2010. Orlando, Fla.

• Russell E. Windsor, MD, can be reached at windsorr@hss.edu.
• Disclosure: Windsor receives educational consulting fees and honoraria from Zimmer, Inc.