An anteroposterior axis of the tibia for total knee arthroplasty.

The objective of the current study was to identify a new extraarticular anatomic landmark indicating the anteroposterior orientation of the tibia using computed tomography. In 39 volunteers (20 males, 19 females), computed tomography scans for healthy right knees in extension were done perpendicular to the tibial shaft axis. The anteroposterior axis of the tibia was defined as a line perpendicular to the transepicondylar axis and passing through the middle of the posterior cruciate ligament. At the level of the tibial plateau and the patellar tendon attachment, the mean medial percentage width of intersecting point of the patellar tendon and the anteroposterior axis was 10.8% +/- 9.8% (range, -9.3% - +30.0%) and -0.2% +/- 10.4% (range, -23.6% -+23.0%), respectively. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment was 0.0 degrees +/- 2.8 degrees (range, -6.3 degrees -+5.2 degrees). The medial border of this attachment therefore can serve as a reliable anterior anatomic landmark to determine the anteroposterior axis of the tibia, and the line connecting the middle of the posterior cruciate ligament and the medial border of the attachment may be useful as a reference axis indicating the anteroposterior orientation of the tibia.