Fig. 4

Histologic features of “acute” and “chronic” osteomyelitis exist in the same lesion. Hematoxylin and eosin-stained, paraffin-embedded, decalcified section of an infected metatarsal bone resected from a patient with a diabetic foot ulcer is shown, illustrating salient features of both acute and chronic osteomyelitis in the same bone. a Low power micrograph of the lesion in which most of the trabecular bone in this part of the metatarsus has been destroyed and replaced by an acute inflammatory reaction, consisting of neutrophils (*) and fibrovascular granulation tissue (black arrow) (scale bar = 1 mm). The inflammation extends to the bone beneath the articular cartilage (yellow arrow) and has destroyed much of the cortical bone (white arrow). Reactive new bone has formed in the lower part of the image, along with a chronic inflammatory and fibrovascular reaction. b A region of interest of acute inflammation (white box in a) is shown highlighting a fragment of dead cortical bone surround by neutrophils (black arrow), with an associated fibrinous exudate, which are hallmarks of acute osteomyelitis (scale bar = 25 mm). c A region of interest of chronic inflammation (black box in a) showing new bone formation (black arrow), and replacement of normal bone marrow with fibrovascular inflammatory tissue (boxed region) (scale bar = 50 mm). d This region of interest (boxed area in c) is presented at high power, showing blood vessels, osteoblasts rimming newly formed woven bone (bottom right), and collections of lymphocytes and plasma cells (arrows), which are characteristic of chronic osteomyelitis (scale bar = 25 mm)