This study assessed the accuracy of the alignment of the lower extremity and the position of the components in a total knee arthroplasty (TKA), which was performed using a computer-assisted navigation system.

This study reviewed 40 TKA using a manual alignment system (group A) and 36 TKA using the Orthopilot. 4.0 navigation system (group B). The radiographs taken 2 months after surgery were used to measure the femoro-tibial angle, the mechanical axis deviation, and the inclination of the femoral and tibial component. A value within the optimum±3° was defined as an ‘acceptable’ and a value over the optimum±3° was befined as an ‘outlier’.

The coronal inclination of the femoral component to the anatomical femoral axis showed outliers in 13 knees in group A and 1 knee in group B. The coronal inclination of the femoral component to the mechanical axis revealed 17 and 2 outliers in each group, respectively. The coronal inclination of the tibial component and sagittal inclination of femoral component showed no significant differences between two groups, but the sagittal inclination of tibial component showed 16 and no outlier in each group, respectively. Concerning the femoro-tibial angle, there were 9 outliers in group A and 2 outliers in group B. The mechanical axis deviation showed 9 and 2 outliers in groups A and B, respectively.

The navigation system helped to produce more ‘acceptable’ and less ‘outlier’ results than the manual alignment system. The alignment of the lower extremity after a TKA can be achieved more accurately using the navigation system.