Fig. 3

Measurement of HKA, FFC, FTC, LFC, and LTC. HKA hip-knee-ankle angle, FFC frontal femoral component angle, FTC frontal tibial component angle, LFC lateral femoral component angle, LTC lateral tibial component angle. a Line a was the femoral mechanical axis, and line b was the tibial mechanical axis; the acute angle formed between them was recorded as the preoperative HKA. b Line c was the postoperative femoral mechanical axis, line d was the line across the bottom of the femoral condyles, line e was the line across the bottom of the tibial plateau on the anteroposterior radiograph, and line f was the postoperative tibial mechanical axis; the lateral angle between line c and line d was recorded as frontal femoral component angle (FFC), the medial angle between line e and line f was recorded as frontal tibial component angle (FTC), and the acute angle between line c and line f was recorded as the postoperative HKA. c Line g was the line connecting the center points of the femoral shaft at 0 cm and 5 cm above the implant, line h was the line across the bottom of the femoral implant, line i was the line across the bottom of the tibial plateau on the lateral radiograph, and line j was the line connecting the center points of the tibial shaft at 5 cm and 15 cm below the joint line; the posterolateral angle between line g and line h was recorded as lateral femoral component angle (LFC), and the posterolateral angle between line i and line j was recorded as lateral tibial component angle (LTC)