Interobserver and Intra-observer Errors in Obtaining Visually Selected Anatomical Landmarks During Registration Process in Non–Image-Based Navigation-Assisted Total Knee Arthroplasty

This study investigated the errors of obtaining visually selected anatomic landmarks for use in the registration process in a passive optical non–image-based computer-assisted total knee arthroplasty system in 5 fresh frozen cadavers. The projected maximum errors in the femoral mechanical axis (due to registration errors of the center of the distal femur) were 0.7° in the coronal and 1.4° in the sagittal plane. The projected maximum errors in the tibial mechanical axis arising from registration errors of the center of the proximal tibia were 1.3° in the coronal and 2° in the sagittal plane. The projected maximum errors in the transepicondylar axis were 9.1° (registration errors of the medial femoral epicondyle) and 7.2° (registration errors of the lateral femoral epicondyle). It should be noted that the results may be partly related to the use of the particular system in this experiment.