Fig. 1

Metaphyseal anteversion measurement at D level: “a” is a line parallel to transepicondylar axis, passing through the point of intersection of “b” and “c” lines; “b” is the line passing through two different points on femoral posterior cortex and represents the posterior cortex axis; “c” is the line passing through two different points on femoral anterior cortex and represents the anterior cortex axis; “d” line is the bisector of the angle formed by anterior and posterior cortex axes and represents the metaphyseal axis. The α angle is equivalent to the angle formed by the anterior cortex axis and the transepicondylar axis, which is defined as anterior cortex anteversion (ACA). The β angle is equivalent to the angle formed by the posterior cortex axis and the transepicondylar axis, and is defined as posterior cortex anteversion (PCA). The θ angle is equivalent to the angle formed between the metaphyseal axis and the transepicondylar axis (metaphyseal axis anteversion: MAA) and, knowing the value of ACA and PCA, could be calculated with the simplified formula shown in the figure