Musculoskeletal ImagingExostosis
a
benign outgrowth of bone projecting from the surface, also termed osteochondroma. An autosomal dominant disorder in which numerous osteochondromas occur with clinical and
radiographic abnormalities is known as
hereditary multiple exostoses. Multiple cartilaginous exostoses are also a feature of
metachondromatosis.
A subungual exostosis arises beneath or adjacent to the nailbed in the distal phalanx of a digit, frequently the great toe (Fig.1). This benign bone tumour may lead to ulceration of the surrounding tissue.
A turret exostosis is a bone excrescence that typically occurs on the dorsal surface of a proximal or middle phalanx of a finger. Often trauma precedes its development. This lesion appears to represent an ossifying subperiosteal haematoma.
DR/RB
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AP (a) and lateral (b) radiographs of the first toe demonstrates a large subungual exostosis arising from the distal phalanx.
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Exostosis, Fig.1 (a) | | Exostosis, Fig.1 (b) | |