Gap Balancing v. Measured Resection Knee Surgery. Who Wins?

In a square-off between gap balancing and measured resection techniques in cementless total knee arthroplasty (TKA), which wins as far as implant migration and tibiofemoral contact kinematics? This is what a team of Canadian researchers set out to learn with their work, “Effect of gap balancing and measured resection techniques on implant migration and contact kinematics of a cementless total knee arthroplasty,” published in The Knee.

The researchers collected data from 19 total knee surgeries with gap balancing patients and 20 total knees with measured resection patients. Each patient received an identical fixed-bearing, cruciate-retaining cementless implant, followed by a baseline radiostereometric analysis (RSA) exam at two weeks postop. Patients returned for follow-up visits at six weeks, three months, six months, and one-year, at which point they had another radiostereometric analysis.

Matthew Teeter, Ph.D. associate professor of Medical Biophysics, Surgery and Medical Imaging at the Schulich School of Medicine & Dentistry, Western University in London, Ontario, Canada, and study co-author explained to OTW how the study came about and what he and his team learned.

“Surgeons have developed preferences for gap balancing or measured resection surgical technique but a new generation of cementless total knee implants are increasingly being used and might be more sensitive to technique-based differences in loading during the early phase of healing compared to cemented knees.”

So, explained Dr. Teeter, the team used RSA to compare fixation and kinematics between techniques together for the first time in a cementless knee design.

At one year, the team found, migration including maximum total point motion did not vary between the two groups, nor did femoral component migration including maximum total point motion.

“The majority of migration occurred on the medial side of the tibial component,” said Dr. Teeter, “where greater loads are expected. We found that regardless of technique, implant migration stabilized from around 3 months to 1-year post-operation, at a magnitude suggesting good long-term fixation will be achieved. Kinematics were driven by the implant design and were also unaffected by technique.”

The results suggests that surgeons can use the gap balancing or measured resection technique they are most comfortable with for this cementless total knee design and expect stable implant fixation in the longer term.