The risk of notching the anterior femoral cortex with the use of navigation systems in total knee arthroplasty

Use of navigation systems has recently been introduced in total knee arthroplasty (TKA) to achieve more reliable prosthetic alignment. In the sagittal plane, there are two important requirements for navigation systems: (1) perpendicular cut to the femoral mechanical axis and (2) prevention of notching of anterior femoral cortex. These two requirements, however, may conflict. The angles between the line of the anterior femoral cortex and four sagittal femoral mechanical axes for navigation systems using radiographs of the entire lower extremity, while standing were measured and compared. These four sagittal axes simulated on the radiographs in navigation systems were in extension relative to the line of the anterior femoral cortex in 40–85% of cases in male and 65–100% in elderly female. The present study showed that navigation systems have the potential risk for notching of anterior femoral cortex.