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. 2025 Mar 21;13:1525542. doi: 10.3389/fbioe.2025.1525542

FIGURE 2.

FIGURE 2

Measurement of the lower limb alignment, HKA, MPTA, PTS, anterior opening gap, and posterior opening gaps. (A) The lower limb alignment is considered to be aligned when a vertical line running from the center of the femoral head passes through the center of the articular plane of the talus and links the medial edge and lateral edge of the tibia. The lower limb alignment ratio is B/(A + B). (B) The HKA angle is formed between the first line connecting the center of the femoral head to the center of the tibia and the second line connecting the center of the tibia to the center of the articular plane of the talus. (C) The MPTA angle is formed between the first tibial anatomical axis and the medial and lateral connecting lines of the second tibial plateau. (D) The anterior and posterior tibial cortex points on the distal end of the joint line at 5 cm and 15 cm, respectively, link the line connecting the anterior and posterior cortical points (Line 1, Line 2). Then, the midpoint of the connecting line is established. The proximal anatomical axis connects the two points (Line 3). A vertical line (Line 5) to the proximal tibial extension line (Line 4) is plotted, and a line (Line 6) between the leading edge and the posterior edge of the medial tibial plateau can be defined. The angle between Line 5 and Line 6 is the PTS angle. (E) The anterior opening gap is measured at the medial edge of the coronal osteotomy site, and the posterior opening gap is measured at the tibia’s most prominent posterior medial edge. HKA, hip-knee-ankle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope; FM, femoral mechanical axis; TM, tibial mechanical axis.