Chapter 12 The locomotor system/Fig 12.13.jpg

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Osteomyelitis is often due to haematogenous spread from foci elsewhere. The bacteria lodge within metaphyseal (hairpin) blood vessels and set up an inflammatory reaction in the medullary canal, which spreads through the cortex, elevates the periosteum and may spread locally into an adjacent joint, causing septic arthritis, or into blood vessels leading to bacteraemia or septicaemia. Interference with blood supply leads to bone death, with formation of a ‘sequestrum’; meantime, the periosteum lays down a shell of new bone, the involucrum. Pus may track to the skin surface forming a discharging sinus.