Erlenmeyer

Erlenmeyer flask deformity is an abnormality of the distal femur. Although rare, Erlenmeyer’s flask deformity can also be observed in other long bones, such as, the proximal ends of the humeri and tibiae and in the distal ends of the ulnae and radii. The deformity can occur on both sides of the body or on one side. The name “erlenmeyer flask” is gleaned from German chemist Richard Erlenmeyer’s laboratory flask that has a base shaped like a cone and a narrow, cylindrical neck joined by uncurved edges. Thus, this deformity is so named because the distal femur resembles a glass flask where the metaphysis is flared in a conical manner and the diaphysis is constricted or narrowed. The deformity consists of an absence of modeling of the di-metaphysis

One such study by Faden et al, allowed the researchers to classify Erlenmeyer’s flask deformity into three groups. The first category describes the typical, common shape of the bone associated with EFD where a normal di-metaphyseal is not present. It is named EFD-T and it appears as a relatively normal trabecular (spongy) bone. This type of EFD is seen in frontometaphyseal dysplasia, craniometaphyseal dysplasia, craniodiaphyseal dysplasia, diaphyseal dysplasia-Engelmann type, metaphyseal dysplasia-Pyle type, Melnick–Needles osteodysplasty, and otopalatodigital syndrome type I. The second category describes the atypical type of EFD (EFD-A) as the bone lacks the normal modeling of the di-metaphyseal and an unusual appearance of the trabecular bone. This form of EFD is commonly seen in dysosteosclerosis and osteopetrosis. Lastly, the third category of EFD describes the the deformity as having a marrow expansion (EFD-ME) where the bone marrow becomes packed with blood cells (hyperplasia) or infiltrated with foreign or abnormal tissue which is commonly seen in Gaucher’s disease.
The most common way to diagnosis Erlenmeyer’s flask deformity is by use of radiography an imaging technique that uses electromagnetic radiation, such as X-rays, to look at an internal structure of an object with varying density (ie., the human body).

This means that presence of this deformity progresses during childhood as the skeleton develops. However, another disorder or condition will be present. One such case allowed physicians to use X-ray in order to diagnosis this condition in an eight year-old boy. This boy presented to Dr. Andras Heczey and Dr. Chrystal Louis, at Baylor College of Medicine with new, onset acute pain in his right leg. Upon examination of the radiograph, Erlenmeyer’s flask deformity was observed as well as a fracture. The patient was diagnosed with neuroblastoma at six months old where he was given treatment with cyclophosphamide and monthly intravenous bisphosphonate therapy. The bisphosphonate therapy was discontinued because of the risks associated with developing osteoporosis. After diagnosis of EFD, this patient underwent several tests to rule out potential causes of EFD, such as, bone marrow disorder, metal poisoning, or hereditary bone diseases. Radiographic images confirmed delineation between osteopetrotic and normal bone which suggested a period of increased bone turnover followed by improved bone growth which is consistent with the bisphosphonate exposure the patient had at six months old. As a result, the patient is a risk for fractures in the areas where there was a transition between the osteopetrotic and normal bone. This case study shows that EFD will occur with another condition and that it can also occur