Intraoperative Load-Sensing Variability During Cemented, Posterior-Stabilized Total Knee Arthroplasty

Load-sensing technology during total knee arthroplasty (TKA) provides objective measurements of ligamentous balance. The purpose of this study is to assess its intraoperative validity and reliability during TKA.

Fifty-four patients underwent TKA using the OrthoSensor VERASENSE tibial insert to assist with ligament balance. The transepicondylar axis (TEA) was used to determine femoral component rotation, and the posterior condylar angle (PCA) was measured. Load measurements were documented at 10°, 45°, and 90° of flexion with the trial (TRIAL) components and with the definitive (FINAL) cemented implants. Adequate balance was defined as a load differential ≤15 pounds between compartments.

Adequate balanced with TRIAL and FINAL implants was observed in 89% TKAs. There was a significant linear correlation of the TRIAL and FINAL loads in the medial compartment throughout range of motion. No correlation between the TRIAL and FINAL loads was identified in the lateral compartment. There was no relationship between an increasing PCA and medial compartment loads at 45° (R² = 0.0006, Y = −0.10X + 7.3 ± 2.3; P = .86) and 90° (R² = 0.004, Y = −0.25X + 6.3 ± 2.1; P = .62) of flexion, suggesting that the compartment loads were not significantly altered with femoral rotation parallel to the TEA. A similar finding was observed in the lateral compartment at all poses.

Variability between the TRIAL and FINAL implant measurements was higher in the lateral compartment as compared to the medial compartment. Using the TEA and not the posterior condylar line as a landmark to guide femoral component rotation, the flexion gap is frequently balanced without the need for additional ligament releases.