Explanation:
In children, acute hematogenous osteomyelitis most commonly affects the metaphysis of long bones. The metaphyseal region contains slow-flowing sinusoidal capillary loops that predispose to bacterial seeding. Additionally, the metaphyseal blood supply forms hairpin loops where bacteria can lodge easily. In infants, transphyseal vessels allow infection to spread into the epiphysis and joint space, whereas in older children the physis acts as a barrier preventing spread to the joint. The most commonly involved bones are the distal femur, proximal tibia, and proximal humerus. Staphylococcus aureus remains the most common causative organism. Reference: Trueta J, 'The three types of acute haematogenous osteomyelitis', Journal of Bone and Joint Surgery (1959).