At what steps in the performance of a TKA do errors occur when manual instrumentation is used?

Computer assisted navigation tools make it possible to measure the accuracy with which each step of a total knee replacement is performed using conventional manual instrumentation. Using these tools, we have shown that the placement of the femoral and tibial cutting blocks using manual instrumentation is inconsistent and often inaccurate. The purpose of this study is to determine when during the performance of each step of a TKR errors occur, and to quantify the magnitude of these errors.