Analysis of the tibial anteroposterior axis and its use in TKA.

Abstract

Objective To investigate the relationship between tibial anteroposterior axis and other anatomic landmarks in determining the rotation of tibial prosthesis in total knee arthroplasty using computed tomography. Methods Transverse CT scans of 40 volunteers' right knee in full extension were made. The anteroposterior axis of the tibia was defined as a line which was perpendicular to the transepicondylar axis and passing through the middle point of the posterior crnciate ligament. At the tibial plateau and optimum re-section level, the mean medial percentage width of intersection point of the patellar tendon anti the antero-posterior axis was measured. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon and the medial 1/3 of the patellar tendon were measured. Results At the tibial plateau level, the mean medial percentage width of intersection point of the patellar tendon was 10.1%±8.3%. At the optimum resection level, the mean medial percentage width of intersection point of the patellar tendon was 0.2%±10.0%. At the optimum resection lev-el, the mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon was 0.1°±2.7°. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament anti the medial 1/3 of the patellar tendon was 10.3°±3.6°. Conclusion There was a tendency to align the tibial component in external rotation relative to the femoral component when the medial 1/3 of the patellar tendon was used. The line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon can be used as a reliable axis for correct rotational orientation of the tibial component. Key words: Arthroplasty; replacement; knee; Tomograph; X-ray computed; Tibia