Fig. 2
Calculation of the adduction moment’s External Frontal-plane Lever arm (EFL) from skeleton dimensions. The relevant straight-line segments (a) are depicted once again in counterclockwise rotated posture (b), which represents the static single-leg-stand situation, with the ground-reaction-force (arrow) acting bottom-up vertically along midline pelvis, and with the tibia-plateau ideally parallel to the ground after osteotomy. The highlighted formulas derived from (b) allow conversion of the MA (in radians) to the EFL and vice versa including further skeleton dimensions, as well as calculation of the lateral distance sTP from the Mikulicz-Line to the knee centre on the tibia plateau. The large-arrow-marked formulas are directly derived from the trigonometric relationships between lengths and angles in (b). Equation (1) results from a usual mathematical approximation of the first, complex formula by a simpler polynomial