Fracture case A 9 months old male Great Dane Dog sustained multiple fractures including a fracture of the humerus - an immediate post-op lateral radiograph was made of the humerus that showed poor stabilization with marked over-riding of the fragments.Post-operative radiograph The dog failed to use the affected limb as expected following treatment - a follow-up radiograph was made 12 days after surgery - what is your explanation for the dog not using the forelimb - the arrow will assist you in making your diagnosis. Radiograph 12 days post-op Radiographic diagnosis The arrow points to a sequestrum which has formed from the distal fragment - the sequestrum retains its original density and there is an absence of any new bone on its surface - a lucent zone has formed around the sequestrum - note that the periosteal new bone involves the entire shaft of the humerus suggesting that it is not the healing response of callus formation expected around the fracture site but is a response to a probable infected soft tissue environment - the bony response is marked considering the length of time following the injury - the nature of the response is influenced by the young age of the patient - the dog developed a generalized infection and was euthanized - the sequestrum is unique in that it forms from a portion of the distal bone fragment instead of from a totally separated bone fragment - this response represents the result of the infarcts within the bone that destroy the blood supply from the distal part of the fragment plus the failure of any new capillary bed to gain entrance to the developing sequestrum from the surrounding infected soft tissue. The general health of the dog was thought to be good at the time of the injury and there was nothing about the patient that suggested the possibiity of a generalized infection especially the development of the sequestrum. Both radiographs are shown for comparison
