Dysplasia epiphysealis hemimelica (Trevor's disease)
Publication Date: 2017-06-22
Small T1 hypointense / T2 isointense lesion along the medial dorsal soft tissues of the right mid foot between the navicular and medial cuneiform bones, with peripheral hypointense margin and internal signal intensity which follows cartilage on all sequences. On the GRE sequence, it becomes bright, similar in signal intensity to the other unossified epiphyseal cartilage. In addition, there is a small synchondrosis with the unossified epiphyseal cartilage which protrudes medially from the medial cuneiform and medial aspect of the navicular.
accessory bone of the foot
This disorder affects epiphyses in children, usually in the lower limb, predominantly the knee and ankle. The lesion is characteristically hemimelic, involving either the medial or lateral aspect of the ossification center, with the former site affected twice as frequently as the latter. The general prevalence has been reported as 1 in 1,000,000, and the etiology is unknown. This disease is nonhereditary. Most patients are first seen between the ages of 2 and 14 years, and the condition is three times more common in boys.
TYPES: Cases are classified into localized, classic, or generalized types. The localized form affects a single bone, usually in the hind foot or ankle. The classic form affects more than one area in a single lower extremity, particularly about the knee and ankle, and accounts for more than two-thirds of cases. In the generalized or severe form, the whole lower limb is involved, from pelvis to foot.
The most common sites in order of decreasing frequency are the distal femur, proximal tibia, talus, tarsal navicular, and first cuneiform. Both upper extremity involvement and bilateral involvement by the disease have been reported but are exceedingly rare.
Radiography typically shows an irregular mass with focal ossification arising from one side of the affected epiphysis or sesamoid bone. The lesions may be single or multiple, enlarge with skeletal growth, and may be associated with joint deformity. With maturation, the lesion ossifies and becomes confluent with the underlying bone.
CT helps in definition of the anatomic relations between the mass and the bone, such as cortical and medullary bone continuity; however, in some cases of epiphyseal or sesamoid bone involvement, this continuity may not be readily apparent and rather one may observe expansion of the entire bone.
MR imaging is accurate in identifying the lesion and determining its anatomic relations. MR imaging is also important to reveal the signal intensity of the lesion and its continuity with the primary site, as well as secondary changes in menisci, tendons, ligaments, and muscle. Gadolinium contrast material may play a role in cases of a complication or a rapidly growing osteochondroma.
Normally, biopsy is not necessary because of the diagnostic radiologic features. The treatment options are simple observation or surgical excision. Surgery should be undertaken if the lesion is causing pain or deformity or interfering with function.
- Araujo CR, Montandon S, Montandon C et-al. Best cases from the AFIP: dysplasia epiphysealis hemimelica of the patella. Radiographics. 26 (2): 581-6. doi:10.1148/rg.262055126