Is the anterior tibial tuberosity a reliable rotational landmark for the tibial component in total knee arthroplasty?

To analyze the morphology of the tibial plateau, we studied 100 computed tomographic scans of arthritic knees and measured the mediolateral (ML) and anteroposterior (AP) dimensions as well as their aspect ratio using 3 reference axes of rotation: transepicondylar axis (TEA), posterior tibial margin (PTM), and anterior tibial tuberosity (ATT) axis. Relative to the TEA, the PTM was internally rotated by 1.6° ± 5.1°, and the ATT externally rotated by 14.8° ± 7.2°. The AP and ML dimensions and aspect ratio differ significantly when the reference axis was ATT compared with PTM or TEA and variations were greater while using ATT axis. Our data demonstrate (1) that design of the tibial component restricts the choice of rotational alignment and (2) that ATT is not a reliable landmark for rotation of the tibial component.