Osteomyelitis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
- Microbes may infect bone via 3 routes:
- Hematogenous seeding
- Contiguous spread of infection to bone from adjacent soft tissue
- Direct inoculation from trauma or orthopedic surgery (including prosthetics)
Staphylococcus aureus is the organism most commonly isolated from all forms of osteomyelitis.
Bloodstream-sourced osteomyelitis is seen most frequently in children, and nearly 90% of cases are caused by Staphylococcus aureus. In infants, S. aureus, Group B streptococci (most common[1]) and Escherichia coli are commonly isolated; in children from 1 to 16 years of age, S. aureus, Streptococcus pyogenes, and Haemophilus influenzae are common. In some subpopulations, including intravenous drug users and splenectomized patients, Gram-negative bacteria, including enteric bacteria, are significant pathogens.[2]
The most common form of the disease in adults is caused by injury exposing the bone to local infection. Staphylococcus aureus is again the most common organism seen in osteomyelitis seeded from areas of contiguous infection, but anaerobes and Gram-negative organisms, including Pseudomonas aeruginosa, E. coli, and Serratia marcescens, are also common, and mixed infections are the rule rather than the exception.[2]
Systemic mycotic (fungal) infections may also cause osteomyelitis. The two most common pathogens involved in such infections are Blastomyces dermatitidis and Coccidioides immitis.
In osteomyelitis involving the vertebral bodies, about half the cases are due to Staphylococcus aureus, and the other half are due to tuberculosis (spread hematogenously from the lungs). Tubercular osteomyelitis of the spine was so common before the initiation of effective antitubercular therapy that it acquired a special name, Pott's disease, by which it is sometimes still known. The Burkholderia cepacia complex have been implicated in vertebral osteomyelitis in intravenous drug abusers. [3]
Factors that may commonly complicate osteomyelitis are fractures of the bone, amyloidosis, endocarditis, or sepsis.
In children, the long bones are usually affected. In adults, the vertebrae and the pelvis are most commonly affected.
Acute osteomyelitis almost invariably occurs in children. When adults are affected, it may be because of compromised host resistance due to debilitation, intravenous drug abuse, infectious root-canaled teeth, or other disease or drugs (e.g. immunosuppressive therapy).
Osteomyelitis is a secondary complication in 1-3% of patients with pulmonary tuberculosis. In this case, the bacteria generally spread to the bone through the circulatory system, first infecting the synovium (due to its higher oxygen concentration) before spreading to the adjacent bone. In tubercular osteomyelitis, the long bones and vertebrae are the ones which tend to be affected.
Gross Pathology
Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology.
Microscopic Pathology
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References
- ↑ Haggerty, Maureen (2002). "Streptococcal Infections". Gale Encyclopedia of Medicine. The Gale Group. Retrieved 2008-03-14.
- ↑ 2.0 2.1 Carek, P.J. (2001-06-15). "Diagnosis and management of osteomyelitis". Am Fam Physician. 63 (12): 2413–20. Unknown parameter
|coauthors=ignored (help) - ↑ Weinstein, Lenny (2007-12-16). "Cervical osteomyelitis caused by Burkholderia cepacia after rhinoplasty". J Infect Developing Countries. 2 (1): 76–77. ISSN 1972-2680. Unknown parameter
|coauthors=ignored (help)