Erlenmeyer flask deformity

Last revised by Dr Sonam Vadera on 27 Dec 2021

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 ends of the femora, however it is also seen in the proximal humeri, tibiae, and the distal radii and ulnae 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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Cases and figures

  • Figure 1: photograph - Erlenmeyer flasks
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  • Case 1: osteopetrosis
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  • Case 2: Gaucher disease
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  • Case 3: Pyle disease
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  • Case 4: rickets
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  • Case 5: pure red cell aplasia
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  • Case 6: hereditary multiple exostoses
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  • Case 7: unknown
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  • Case 8: multiple hereditary exostosis
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  • Case 9: osteopetrosis
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