The anteroposterior axis of the tibia in total knee arthroplasty for chinese knees

The goal of this study was to corroborate the use of Akagi's anteroposterior (AP) axis as a rotation reference axis for the tibial component. Transverse computed tomography (CT) scans of the knees of 20 healthy Chinese men (mean age, 34.2±7.9 years; range, 20-43 years) and 20 healthy Chinese women (mean age, 36.7±5.8 years; range, 25-48 years) were obtained. Measurements taken from CT slices at the level of the tibial plateau revealed a mean percentage of the patellar tendon intersected by the AP axis from its medial border of 8%±8.1% (range, 8.1%-23.5%). When the defined AP axis was superimposed on CT slices at the level of the patellar tendon attachment, mean percentage of the width of the patellar tendon intersected by the AP axis from its medial border was 0.2%±10%. Mean angle measurement of angle α was 0.1°±2.7° (range, -5.1° to 5.8°). Mean angle measurement of angle β, or the angle created by the AP axis and the medial third of the patellar tendon from the middle of the posterior cruciate ligament, was 10.3°±3.6° (range, 2.4°-18.8°). The study confirms that Akagi's AP line is reproducible and reliable. The AP line can be used as a rotation reference axis for the tibial component during preoperative CT scanning of the knee.