Musculoskeletal ImagingSequestrum
a fragment of necrotic bone that becomes separated from healthy bone. Sequestra may occur in various conditions, such as
osteomyelitis, tuberculous arthritis, tropical ulcer and non-Hodgkin's
lymphoma (
Fig.1).
In haematogenous osteomyelitis, a sharply marginated bone lesion is seen as radiodense bone spicules caused by osseous necrosis. The sequestrum frequently lies in a space surrounded by granulation tissue. In some cases the sequestrum may break through the cortex and enter the soft tissues, sometimes being discharged through draining sinuses. Sequestra are best visualized using conventional tomography, CT scanning and, in some cases, MR imaging.
A ring sequestrum may develop as a consequence of pin tract infection.
DR/RB
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AP (a) and lateral (b) radiographs of the femur demonstrate a healed fracture of the femoral diaphysis. A large rod-like sequestrum is observed in the medullary canal owing to chronic osteomyelitis.
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Sequestrum, Fig.1 (a) | | Sequestrum, Fig.1 (b) | |