Propagation of errors in two methods for determining tibial contact locations using single-plane fluoroscopy following total knee arthroplasty

Abstract

ABSTRACTAnalysis of anterior–posterior (A–P) tibial contact locations following total knee arthroplasty (TKA) provides an objective assessment of the relative motion of the tibia on the femur during activities of daily living. Determining A–P tibial contact locations using single-plane fluoroscopy requires input in the form of the relative 3D position and orientation of the components. Although errors in the relative 3D position and orientation of the components have been quantified, it is unknown how these errors propagate into errors in the A–P tibial contact locations. To assess the propagation of errors for two methods used to calculate A–P tibial contact locations, 1000-iteration Monte Carlo simulations were performed for different reference relative 3D positions and orientations of the femoral component. For each iteration, random errors were added to each of the six degrees of freedom of the reference relative 3D position and orientation and the A–P tibial contact locations were calculated using the closest point method and the penetration method. The root mean squared errors (RMSEs) for the closest point method and penetration method were 1.2 mm and 2.4 mm, respectively. Errors in the A–P tibial contact location due to errors in the relative 3D position and orientation of the components place a lower bound on the errors in computing A–P tibial contact location for each method. The RMSEs of 1.2 mm and 2.4 mm for the closest point and penetration methods, respectively, were due primarily to random errors and indicate that both methods have the potential to provide objective assessment of A-P tibial contact locations following TKA.