Evaluation of accuracy in ankle center location for tibial mechanical axis identification.

Many surgical computer-assisted systems use mechanical axis identification as a reference for their computations. The goal of this study was to compare three methods to determine the location of the distal point of the tibial mechanical axis, based on percutaneous digitization of definite anatomical landmarks. In particular, we evaluated the accuracy of the identified tibial mechanical axis and the repeatability of the obtained results. Tests performed by four surgeons on cadaveric knees showed that the variability in identifying the ankle center using two out of the three methods presented introduced an inaccuracy in the mechanical axis identification of around 1 degrees. This makes their use suitable for computer-assisted systems.