The Erlenmeyer flask bone deformity in the skeletal dysplasias.

Erlenmeyer flask bone deformity (EFD) is a long-standing term used to describe a specific abnormality of the distal femora. The deformity consists of lack of modeling of the di-metaphysis with abnormal cortical thinning and lack of the concave di-metaphyseal curve resulting in an Erlenmeyer flask-like appearance. Utilizing a literature review and cohort study of 12 disorders we found 20 distinct disorders were associated with EFD.