Tibial Contact Force and Contact Location Errors of the VERASENSE

The OrthoSensor VERASENSE knee system is a commercially available instrumented tibial insert that provides real-time intraoperative measurements of tibial contact force and contact location to guide surgeons toward improving outcomes in total knee arthroplasty (TKA). However, the device has been used contrary to the manufacturer's instructions in several studies and lacks published information on accuracy. Therefore, the primary objectives of this study were to evaluate the device's error in tibial contact force when used according to and contrary to the manufacturer's instructions, and also to evaluate the device's error in anterior-posterior (A-P) and medial-lateral (M-L) contact locations. The error in tibial contact force in one-compartment distributed loading was evaluated by applying known forces in ranges within and exceeding that instructed by the manufacturer, with rezeroing as instructed by the manufacturer, and without rezeroing. The error in tibial contact location in one-compartment concentrated loading was evaluated by applying known forces at known locations on the articular surface. Exceeding the maximum allowable load and not rezeroing did not adversely affect the bias (i.e., average error) (p > 0.05). The maximum absolute bias without rezeroing was 2.9 lbf. Rezeroing more than doubled the bias. The maximum root-mean-squared error in tibial contact location was 1.5 mm in the A-P direction. The device measures tibial contact force with comparable error well above the maximum allowable load and without rezeroing, contrary to the manufacturer's instructions.