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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Radiologically, the earliest sign of osteomyelitis is -
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The correct answer is  Osteomyelitis is the infection of bone by microorganisms. It can be acute or chronic. 
Acute osteomyelitis: This can be primary (haematogenous)or secondary(following open fracture or bone operation). Staphylococcus aureus is the commonest causative organism. C/f: Child presents with an acute onset of pain and swelling at end of a bone, associated with systemic features of infection like a fever. 
Investigations: Blood- polymorphonuclear leucocytosis and an elevated ESR. X-rays - The earliest sign to appear in X-ray is a periosteal new bone deposition at metaphysics. This is called periosteal reaction. It takes about 7-10 days to appear. Bone scan- bone scan using Tc 99 may show increased uptake by bone in the metaphysis.