SEARCH RESULTS FOR: Bacterial-Osteomyelitis

Bacterial-Osteomyelitis

Bacterial Osteomyelitis: Pathogenesis and clinical findings Authors: Mehul Gupta Reviewers: Stephen Vaughan* Yan Yu* * MD at time of publication Iatrogenic: Penetrating medical procedure introduces bacteria directly to bone Systemic immune reaction Macrophages, neutrophils and dendritic cells are activated by recognizing bacterial pathogen associated molecular patterns (PAMPs) Trauma: Penetrating injury or open fracture introduces bacteria directly to bone Hematogenous: Blood carries bacteria from distant site of infection to bone Contiguous: Neighboring site of infection seeds bacteria directly to bone Bacterial Osteomyelitis Innate Immune cells and local mast cells release vasoactive cytokines Capillaries dilate to ↑blood flow to affected area and become more permeable to allow for exit of immune cells and plasma contents Localized Immune response Poorly understood mechanismsàinnate immune systems unable to clear the bacteria in some individualsàchronic infection Immune cells produce pyrogenic intermediates (i.e. PGE2, IL-6, and IL-1) Pyrogenic intermediates travel through the bloodstream to the hypothalamus and alters the body’s thermal setpoint Fever Immune cells produce inflammatory cytokines (i.e. TNFα and IL6) Systemic inflammatory cytokines result in the production of Non-specific acute- phase reactants High Serum CRP and ESR Warmth Erythema Progressive blood vessel occlusion by immune cellular and bacterial debris causing infarct and necrosis of bone More permeable capillaries allow plasma to leak into surrounding periosteal tissue More permeable capillaries allow macrophages and neutrophils to exit the capillaries at the site of infection Immune cells phagocytize bacteria, producing an of opaque off-white fluid Pus Immune cells sequester necrotic bone tissue into a regional abscess within medullary bone Sequestrum seen as localized opacity on CT or late X-ray imaging ↑ Osteoclast activity to remove damaged medullary bone and ↑ Osteoblast activity to reform new bone Osteoclasts and osteoblasts remodel and deposit new bone in area surrounding necrotic tissue Swelling ↑ Periosteal fluid applies ↑ pressure to surrounding nerve endings Bone Pain manifesting as refusal to use limb New layer of bone formed Positive Bone Scan in area of infection Abbreviations: • IL – Interleukin • PGE2 – Prostaglandin E2 • TNFα – Tumor necrosis factor alpha Involucrum / Periosteal Reaction: seen as regional luminance surrounding sequestrum on CT or late X-ray imaging Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published May 21, 2021 on www.thecalgaryguide.com