Osteomyelitis
(Background
Infection of a bone.)
Pathophysiology-
• Infection can come from direct/contiguous spread (cellulitis, abscess, trauma, surgery prosthesis), or haematogenous spread, which is commoner in kids, patients with urinary catheters, or TB.
• Once infected, leukocytes enter bone, releasing enzymes which cause bone lysis and leave necrotic areas known as sequestra. New bone often forms around this.
• Chronic osteomyelitis if >6 months of infection.
Pathogens
• Staph. aureus is the commonest cause in most patient groups.
• Less common pathogens include Strep. pyogenes (kids), H. influenzae (kids), Gram negative bacilli (elderly), and Pseudomonas aeruginosa (IV drug users).
• In sickle cell disease, Salmonella is the commonest cause.