6. Bone Infections

6. Bone Infections - Pathogenesis I Infections of the Bones...

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Infections of the Bones and Joints Osteomyelitis Pathogenesis I • Bone is metabolically active-- collagen and and mineral are actively remodeled – Children have growing bones – Elderly can have net loss - > brittle bones Contains: • Afferent arterial loops (no phagocytes) • Efferent loops have functionally inactive lining cells and turbulent flow Pathogenesis II Children: • Infection occurs in rapidly growing bones, primarily in metaphysis of long bones • 85% of infections in children <16yrs • infection contained by epiphyseal growth plate (1yr- puberty), extends to periosteum • infection spreads to epiphysis via perforating capillaries and growth plate destruction results • can lead to septic arthritis in children <1yr • Less damaging in adults Pathogenesis III • Acute suppurative (pussy) infection - > vascular obstruction + pus (enzymes) - > low pH - > pressure±- > edema • results in tissue necrosis, bone trabuculae (fins) break down, dissolving of calcium and matrix, spread via canals to cause vascular compromise • can lead to sequestrum (“floaties”) formation, abscess cortical destruction and pathological failure Types of Osteomyelitis I Hematogenous (spread by blood) • seen in children and adults >50 and occurs in long bones of lower extremities • caused by one of: Staphylococcus aureus, enteric gram negative baccilli , Haemophilus influenzae
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This note was uploaded on 05/09/2010 for the course LMP 232 taught by Professor Crandall during the Spring '10 term at University of Toronto.

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6. Bone Infections - Pathogenesis I Infections of the Bones...

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