Metaphyseal diaphyseal angle

The metaphyseal-diaphyseal angle (of Drennan) is an important measurement used to distinguish between tibia vara (Blount disease) and physiological bowleg.

Measurement

This angle is measured by drawing a line along the long axis of the tibia, creating a perpendicular to this line, and drawing another line through axial plane of the proximal tibial metaphysis. The angle created between the perpendicular line shown and the metaphyseal line is the metaphyseal diaphyseal angle.

Interpretation

It is abnormal if >11, indicating Blount disease.