Osteomyelitis can affect both adults and children. The bacteria or fungus that can cause osteomyelitis, however, differs among age groups. In adults, osteomyelitis often affects the vertebrae and the pelvis. In children, osteomyelitis usually affects the adjacent ends of long bones. Long bones (bones of the limbs) are large, dense bones that provide strength, structure, and mobility. They include the femur and tibia in the legs and the humerus and radius in the arms. In general, osteomyelitis must extend at least 1 cm and compromise 30 to 50% of bone mineral content to produce noticeable changes in plain radiographs.
Early findings may be subtle, and changes may not be obvious until 5 to 7 days in children and 10 to 14 days in adults.
Typical early bony changes include: periosteal thickening, lytic lesions, endosteal scalloping, osteopenia, loss of trabecular architecture, and new bone apposition.The distinguishing feature of chronic osteomyelitis is necrotic bone, which is formed in an average of 10 days, nevertheless plain radiographs are unable to detect sequestra or sclerotic bone for many weeks. Periostitis, involucrum formation, and sinus tracts are due to subperiosteal abscess with lifting of the periosteum, new bone formation, and soft tissue fistulas.