Comparison of registration procedures of the tibia in robot-assisted total knee arthroplasty

The authors have implemented registration procedures by means of an intramedullary rod and by means of surface matching in their robot-assisted procedure for milling the tibia in TKA. Registration by means of an intramedullary rod is a simple and fast procedure that does not need CT-images. The accuracy is better than 2degrees in the frontal plane. In case of a very deformed tibia or when the tibia is equipped with intramedullary nails from a previous operation however, it is not suitable. Registration using surface matching is an accurate and generally usable procedure. The difference between the predicted and the real orientation is less than 1.1degrees in the frontal plane and less than 0.5degrees in the sagittal plane. These registration procedures need immobilization of the tibia. Rigid immobilization is not necessary in case the registration is performed dynamically.