This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Periosteal reaction in a case of acute osteomyelitis can be seen earliest at: March 2012 
Select and explain. 
A. 5 days, B. 10 days, C. 15 days, D. 20 days
B: 10 days
Answer: B: 10 days 
Explanation: Ans: B i.e. 10 days The earliest sign to appear on the X-ray is a periosteal new bone deposition (periosteal reaction) at the metaphysis. It takes about 7-10 days to appear Osteomyelitis Earliest site of involvement: Metaphysis Diagnosis of acute OM: Blood culture (positive in 65% cases) Periosteal reaction seen in acute OM appears after: 10 days MC organism in acute OM: Staph. aureus Brodies abscess: - Equilibrium between host & organism; - Abscess cavity remains without fuher enlargement