Accuracy of Balancing at Total Knee Surgery Using an Instrumented Tibial Trial

Abstract

Background: Balancing is an important part of a total knee procedure, and in recent years, more emphasis has been given to quantifying the process.

Methods: During 101 total knee surgeries, initial bone cuts were made using navigation. Lateral and medial contact forces were determined throughout flexion using an instrumented tibial trial. Balancing was defined as a ratio of the medial and total force, the target being 0.5 (equal lateral and medial forces). Based on the initial values, surgical corrections were selected to achieve balancing. The most common corrections were soft tissue releases (63 incidences), including MCL, posterolateral corner, posteromedial corner, and changing tibial insert thicknesses (34 incidences).

Results: After final balancing, the mean ratio was 0.52 ± 0.14, between 0.35 and 0.65 being achieved in 80% of cases. In 84% of cases, only 0-2 corrections were required. The average total force on the condyles was 215 ± 86 N.

Conclusion: Our study provides data to surgeons on the results to expect when balancing a knee, which can enhance both accuracy and consistency of the procedure.

Keywords: contact forces; instrumented tibial trial; ligament balancing; soft tissue balancing; total knee.