Antero-posterior axis of tibia in patient undergoing total knee replacement in Indian population.

Aim of this CT- based study was to find out a reliable anatomical axis for proper rotational placement of the tibial component during knee replacement surgery in the Indian population. CT scanning was performed pre-operatively on all the 45 patients (13 men, 32 women, total 68 knees) due to undergo knee replacement for osteo-arthritic knees. The tibial anteroposterior (AP) axis is defined as a line drawn perpendicular to the surgical epicondylar femoral axis and passing through the center of posterior cruciate ligament (PCL) attachment. Angles between various anatomic landmarks and the defined tibial AP axis were identified. The mean angle between line connecting the medial border of patellar tendon and centre of PCL and the defined tibial AP axis was 0.06 (-5 to 7; SD 2.65) and was closest to defined AP axis of tibia. This axis remained the closest irrespective of the varying femoro-tibial angle and severity of tibial bowing. In our patients, the line connecting the medial border of patellar tendon to the centre of the PCL has been found to be an independent, reliable and reproducible rotational axis for placing the tibial trial and definitivite prosthesis. This is particularly helpful for those surgeons, who prepare the femur earlier than the tibial cut and trial. This tibial AP axis along with other anatomical landmarks is a reliable and reproducible landmark for implanting the tibial prosthesis in a proper rotational alignment in the Indian population.