Erlenmeyer flask deformity

Last revised by Calum Worsley on 21 Jul 2022

Erlenmeyer flask deformity (EFD), also known as metaphyseal flaring, refers to a radiographic appearance typically on a femoral radiograph demonstrating relatively reduced constriction of the diaphysis and flaring of the metaphysis as a result of undertubulation

The name refers to the resemblance to a flat bottomed titration flask used by chemists (known as a conical flask in British English).

It has been classically used with reference to the distal end of the femur, however it is also seen in the proximal humerus, tibia, and the distal radius and ulna 4

The causes can also be remembered with the mnemonics AP OF DR GHLNCHONG or Lead GNOME.

The conically-shaped flask with a wide base and short narrow neck was created by the German chemist Emil Erlenmeyer (1825-1909) in 1860 3.

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