Rotational alignment of the tibial component in total knee arthroplasty.

This study compares two different methods of aligning the tibial component in a total knee arthroplasty, one by aligning the component with the border between the medial one third and lateral two thirds of the tibial tubercle and the other by allowing the component to seek its own position as the knee is taken through a range of motion. The first technique emphasizes the need to maintain an appropriate quadriceps angle for optimum patellar tracking and the second method optimizes femorotibial kinematics. The two methods suggest different positions for the tibial component, with the tibial component internally rotated an average of 5.6 mm from the border between the medial one third and lateral two thirds of the tibial tubercle when allowed to seek its own rotation. Surgeons must be aware of the choices they are making when selecting a method of aligning the tibial component. The prosthesis used in this study had a relatively high level of rotational constraint. The situation is somewhat different in a less constrained design.