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==Overview==
Entry of the organism into bone is the first step in the development of osteomyelitis and occurs by three main mechanisms; hematogenous seeding, contiguous spread of infection to bone from adjacent soft tissue, and direct inoculation from trauma or orthopedic surgery (including [[prostheses]]).<ref name="pmid4001933">{{cite journal |vauthors=Gristina AG, Oga M, Webb LX, Hobgood CD |title=Adherent bacterial colonization in the pathogenesis of osteomyelitis |journal=Science |volume=228 |issue=4702 |pages=990–3 |year=1985 |pmid=4001933 |doi= |url=}}</ref><ref name="pmid17010697">{{cite journal |vauthors=Clarke SR, Foster SJ |title=Surface adhesins of Staphylococcus aureus |journal=Adv. Microb. Physiol. |volume=51 |issue= |pages=187–224 |year=2006 |pmid=17010697 |doi=10.1016/S0065-2911(06)51004-5 |url=}}</ref>
 
Microbial and host factors contributing to the pathological process of the disease may vary from one patient to another. In children, the [[long bone]]s are usually affected. Acute osteomyelitis almost invariably occurs in children. In adults, the vertebrae and the [[pelvis]] are most commonly affected, possibly due to the compromised host resistance as a result of debilitation, [[intravenous]] [[substance abuse]], infectious [[root canal|root-canaled]] teeth, or other disease or drugs (e.g., [[Immunosuppressant therapy|immunosuppressive therapy]]).
 
==Pathophysiology==
==Pathophysiology==
*Microbes may infect bone via 3 routes:
Entry of the organism into bone is the first step in osteomyelitis and occurs by three main mechanisms:<ref name="pmid4001933">{{cite journal |vauthors=Gristina AG, Oga M, Webb LX, Hobgood CD |title=Adherent bacterial colonization in the pathogenesis of osteomyelitis |journal=Science |volume=228 |issue=4702 |pages=990–3 |year=1985 |pmid=4001933 |doi= |url=}}</ref><ref name="pmid17010697">{{cite journal |vauthors=Clarke SR, Foster SJ |title=Surface adhesins of Staphylococcus aureus |journal=Adv. Microb. Physiol. |volume=51 |issue= |pages=187–224 |year=2006 |pmid=17010697 |doi=10.1016/S0065-2911(06)51004-5 |url=}}</ref>
#Hematogenous seeding
#Hematogenous seeding
#Contiguous spread of infection to bone from adjacent soft tissue
#Contiguous spread of infection to bone from adjacent soft tissue
#Direct inoculation from trauma or orthopedic surgery (including prosthetics)
#Direct inoculation from trauma or orthopedic surgery (including [[prostheses]]).
 
Mechanism of disease:
Generally, microorganisms may infect bone through one or more of three basic methods: via the [[bloodstream]], contiguously from local areas of infection (as in [[cellulitis]]), or penetrating [[Physical trauma|trauma]], including [[iatrogenic]] causes such as [[joint replacement]]s or internal fixation of [[Bone fracture|fracture]]s or [[endodontic therapy|root-canaled]] teeth. Once the bone is infected, [[leukocyte]]s enter the infected area, and in their attempt to [[phagocytosis|engulf]] the infectious organisms, release [[enzyme]]s that [[Lysis|lyse]] the bone. [[Pus]] spreads into the bone's blood vessels, impairing their flow, and areas of devitalized infected bone, known as sequestra, form the basis of a chronic infection. Often, the body will try to create new bone around the area of [[necrosis]]. The resulting new bone is often called an [[involucrum]]. On [[histology|histologic]] examination, these areas of necrotic bone are the basis for distinguishing between [[Acute (medicine)|acute]] osteomyelitis and [[wikt:chronic|chronic]] osteomyelitis. Osteomyelitis is an infective process which encompasses all of the bone ([[wikt:osseous|osseous]]) components, including the bone marrow. When it is chronic it can lead to bone [[sclerosis]] and deformity.
 
In [[infant]]s, the infection can spread to the [[joint]] and cause [[arthritis]]. In children, large subperiosteal abscesses can form because the [[periosteum]] is loosely attached to the surface of the bone.
 
Because of the particulars of their blood supply, the [[tibia]], [[femur]], [[humerus]], [[vertebra]], the [[maxilla]], and the mandibular bodies are especially susceptible to osteomyelitis. However, abscesses of any bone may be precipitated by trauma to the affected area. Many infections are caused by ''[[Staphylococcus aureus]]'', a member of the normal [[flora (microbiology)|flora]] found on the [[skin]] and [[mucous membrane]]s.
 
''[[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 streptococcal infection|Group B streptococci]] (most common<ref name="CBC">{{cite encyclopedia|url=http://www.healthline.com/galecontent/streptococcal-infections-1|title=Streptococcal Infections|first=Maureen|last=Haggerty|encyclopedia=Gale Encyclopedia of Medicine|publisher=The Gale Group|year=2002|accessdate=2008-03-14}}</ref>) 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 [[splenectomy|splenectomized]] patients, [[Gram-negative bacteria]], including enteric bacteria, are significant pathogens.<ref name="carek">{{cite journal|last=Carek|first=P.J.|coauthors=L.M. Dickerson; J.L. Sack|title=Diagnosis and management of osteomyelitis.|journal=[[American Family Physician|Am Fam Physician]]|date=2001-06-15|volume=63|issue=12|pages=2413-20}}</ref>
===Pathogenesis===
Several factors contributing to the pathogenesis of osteomyelitis include microbial factors and host factors.


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 [[anaerobe]]s 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.<ref name="carek" />
====Microbial factors====
*Etiologic pathogen possesses numerous cell-wall associated adhesins mediating specific attachment to a wide variety of [[Extracellular matrix protein|extracellular matrix proteins]] found in bone including, [[fibronectin]], [[laminin]], [[osteopontin]], [[bone sialoprotein|bone matrix sialoprotein]], and [[collagen]].<ref name="pmid17010697">{{cite journal |vauthors=Clarke SR, Foster SJ |title=Surface adhesins of Staphylococcus aureus |journal=Adv. Microb. Physiol. |volume=51 |issue= |pages=187–224 |year=2006 |pmid=17010697 |doi=10.1016/S0065-2911(06)51004-5 |url=}}</ref>
*After attachment to the [[bone matrix]], direct toxin effect of pathogen may lead to tissue [[necrosis]].
*Adherent bacterial growth leads to the formation of a [[biofilm]] (an adherent consortium of micro-organisms enmeshed in an exocellular [[polysaccharide]]).<ref name="pmid6472832">{{cite journal |vauthors=Gristina AG, Costerton JW |title=Bacterial adherence and the glycocalyx and their role in musculoskeletal infection |journal=Orthop. Clin. North Am. |volume=15 |issue=3 |pages=517–35 |year=1984 |pmid=6472832 |doi= |url=}}</ref>
*Biofilm pathogens are more resistant to host defense and are able to survive longer than usual.<ref name="pmid6472832">{{cite journal |vauthors=Gristina AG, Costerton JW |title=Bacterial adherence and the glycocalyx and their role in musculoskeletal infection |journal=Orthop. Clin. North Am. |volume=15 |issue=3 |pages=517–35 |year=1984 |pmid=6472832 |doi= |url=}}</ref>


Systemic [[mycotic]] (fungal) infections may also cause osteomyelitis. The two most common pathogens involved in such infections are [[Blastomyces dermatitidis]] and [[Coccidioides immitis]].
====Host factors====
Host factors that may contribute to the pathogenesis of osteomyelitis are subdivided into factors that are involved in hematogenous spread and factors that may contribute to contiguous spread.


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 [[lung]]s). 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. <ref>{{cite journal|url=http://www.jidc.org/issn1972-2680/current-issue/59-vol-2-no-1-february-2008/152-cervical-osteomyelitis-caused-by-burkholderia-cepacia-after-rhinoplasty
=====Hematogenous spread=====
|title=Cervical osteomyelitis caused by Burkholderia cepacia after rhinoplasty|journal=[[Journal of Infection in Developing Countries|J Infect Developing Countries]]|first=Lenny|last=Weinstein|coauthors= Knowlton, Christin A.; Smith, Miriam A.|date=2007-12-16|volume=2|issue=1|pages=76-77|issn=1972-2680}}</ref>
*The pathogen colonizes  the [[metaphysis]] of a large long bone below the growth plate.
*In adults, after closure of the [[growth plate]], the [[Metaphyseal|metaphysea]]<nowiki/>l and [[epiphyseal]] vessels establish reconnections so bacteria entering the nutrient artery are directed to the vascular loops beneath the [[articular cartilage]].
*Accordingly, acute hematogenous osteomyelitis in infants and adults often affects the '''[[epiphysis]]'''.
*In children the growth plate acts as an barrier and the infection is limited to the '''[[metaphysis]]'''.<ref name="pmid19305968">{{cite journal |vauthors=Jansson A, Jansson V, von Liebe A |title=[Pediatric osteomyelitis] |language=German |journal=Orthopade |volume=38 |issue=3 |pages=283–94 |year=2009 |pmid=19305968 |doi=10.1007/s00132-008-1402-6 |url=}}</ref>
*Extension across the growth plate is impeded in children but after closure of growth palate, joint involvement becomes possible.
*In the [[spine]], blood-borne pathogens usually localize to the '''subchondral''' regions of the [[vertebral body]].


Factors that may commonly complicate osteomyelitis are fractures of the bone, [[amyloidosis]], [[endocarditis]], or [[sepsis]].
=====Contiguous spread=====
*In contiguous spread, bone adjacent to a [[cutaneous]] or [[mucosal]] ulcer or soft tissue abscess are affected.
*It is more commonly observed in the setting of [[periodontal]] and sinus disease, [[cellulitis]] of [[Diabetic foot|diabetic feet]], [[epidural abscess]], [[decubitus ulcer]], or [[septic arthritis]].<ref name="pmid19035067">{{cite journal |vauthors=Bluestein D, Javaheri A |title=Pressure ulcers: prevention, evaluation, and management |journal=Am Fam Physician |volume=78 |issue=10 |pages=1186–94 |year=2008 |pmid=19035067 |doi= |url=}}</ref><ref name="pmid26670675">{{cite journal |vauthors=van Asten SA, La Fontaine J, Peters EJ, Bhavan K, Kim PJ, Lavery LA |title=The microbiome of diabetic foot osteomyelitis |journal=Eur. J. Clin. Microbiol. Infect. Dis. |volume=35 |issue=2 |pages=293–8 |year=2016 |pmid=26670675 |pmc=4724363 |doi=10.1007/s10096-015-2544-1 |url=}}</ref>
*In this setting, the inflammatory process must first destroy the [[periosteum]] or [[articular surface]] before it accesses the [[bone]].
*Unlike hematogenous osteomyelitis, the cortex instead of the [[medullary cavity]] is initially infected, and the site at which this occurs influences the rapidity of spread and extent of disease.


In children, the [[long bone]]s are usually affected. In adults, the vertebrae and the [[pelvis]] are most commonly affected.
===Pathologic process===
*Pathogens trigger inflammation and due to this inflammatory process, intraosseous pressure inside the tight [[bone matrix]] increases and may lead to thrombosis of bone vasculature that finally results in bone death.
*If the infection progresses, pus may track to other areas of the bone along the [[medullary canal]] or through the [[Haversian systems]] in cortical bone from the medulla to the outer surface of the cortex and form a '''subperiosteal abscess'''.
*This may contribute to bacteremia or it may track out into the soft tissues and eventually form abscesses or a sinus tract draining to the outside.
*Dead bone accelerates biofilm formation.
*Both the inflammatory [[cytokines]] and mediators released during infection, and in some cases bacterial products themselves, can trigger bone resorption either by [[osteoclast]] activation or by stimulating [[phagocytic cells]] to take on a bone-resorbing phenotype.<ref name="pmid16651071">{{cite journal |vauthors=Lau YS, Wang W, Sabokbar A, Simpson H, Nair S, Henderson B, Berendt A, Athanasou NA |title=Staphylococcus aureus capsular material promotes osteoclast formation |journal=Injury |volume=37 Suppl 2 |issue= |pages=S41–8 |year=2006 |pmid=16651071 |doi=10.1016/j.injury.2006.04.008 |url=}}</ref>
*Bone loss starts around the dead area, resulting in the separation of the dead area of bone from the surrounding living bone, ultimately, forming the'''[[Sequestrum]]'''.
*When periosteal stripping occurs, the resulting periosteal reaction produces a shell of new bone; the '''[[Involucrum]]''', around the dead bone.  


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).
===Associated conditions===
*Factors that may commonly complicate osteomyelitis are fractures of the bone, [[amyloidosis]], [[endocarditis]], or [[sepsis]].


Osteomyelitis is a secondary [[complication (medicine)|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.
*Osteomyelitis is a secondary [[complication (medicine)|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 often affected.


===Gross Pathology===
===Gross Pathology===
[[Image:Osteomyelitis in cancer.jpg|thumb|left|250px|Osteomyelitis in cancer. <br> [http://www.peir.net Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]. ]]
[[Image:Osteomyelitis in cancer.jpg|thumb|left|250px|Osteomyelitis in cancer. <br> [http://www.peir.net Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]. ]]
<br clear="left"/>
<br clear="left"/>
===Microscopic Pathology===
===Microscopic Pathology===
{{#ev:youtube|KTfOwYS1ykY}}
{{#ev:youtube|KTfOwYS1ykY}}


==References==
==References==
{{Reflist|2}}


{{Reflist|2}}
[[Category:Needs overview]]
[[Category:Orthopedics]]
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[[Category:Bacterial diseases]]
[[Category:Emergency mdicine]]
[[Category:Skeletal disorders]]
[[Category:Disease]]
[[Category:Up-To-Date]]
[[Category:Infectious disease]]
[[Category:Infectious disease]]
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2]

Overview

Entry of the organism into bone is the first step in the development of osteomyelitis and occurs by three main mechanisms; hematogenous seeding, contiguous spread of infection to bone from adjacent soft tissue, and direct inoculation from trauma or orthopedic surgery (including prostheses).[1][2]

Microbial and host factors contributing to the pathological process of the disease may vary from one patient to another. In children, the long bones are usually affected. Acute osteomyelitis almost invariably occurs in children. In adults, the vertebrae and the pelvis are most commonly affected, possibly due to the compromised host resistance as a result of debilitation, intravenous substance abuse, infectious root-canaled teeth, or other disease or drugs (e.g., immunosuppressive therapy).

Pathophysiology

Entry of the organism into bone is the first step in osteomyelitis and occurs by three main mechanisms:[1][2]

  1. Hematogenous seeding
  2. Contiguous spread of infection to bone from adjacent soft tissue
  3. Direct inoculation from trauma or orthopedic surgery (including prostheses).

Pathogenesis

Several factors contributing to the pathogenesis of osteomyelitis include microbial factors and host factors.

Microbial factors

Host factors

Host factors that may contribute to the pathogenesis of osteomyelitis are subdivided into factors that are involved in hematogenous spread and factors that may contribute to contiguous spread.

Hematogenous spread
  • The pathogen colonizes the metaphysis of a large long bone below the growth plate.
  • In adults, after closure of the growth plate, the metaphyseal and epiphyseal vessels establish reconnections so bacteria entering the nutrient artery are directed to the vascular loops beneath the articular cartilage.
  • Accordingly, acute hematogenous osteomyelitis in infants and adults often affects the epiphysis.
  • In children the growth plate acts as an barrier and the infection is limited to the metaphysis.[4]
  • Extension across the growth plate is impeded in children but after closure of growth palate, joint involvement becomes possible.
  • In the spine, blood-borne pathogens usually localize to the subchondral regions of the vertebral body.
Contiguous spread

Pathologic process

  • Pathogens trigger inflammation and due to this inflammatory process, intraosseous pressure inside the tight bone matrix increases and may lead to thrombosis of bone vasculature that finally results in bone death.
  • If the infection progresses, pus may track to other areas of the bone along the medullary canal or through the Haversian systems in cortical bone from the medulla to the outer surface of the cortex and form a subperiosteal abscess.
  • This may contribute to bacteremia or it may track out into the soft tissues and eventually form abscesses or a sinus tract draining to the outside.
  • Dead bone accelerates biofilm formation.
  • Both the inflammatory cytokines and mediators released during infection, and in some cases bacterial products themselves, can trigger bone resorption either by osteoclast activation or by stimulating phagocytic cells to take on a bone-resorbing phenotype.[7]
  • Bone loss starts around the dead area, resulting in the separation of the dead area of bone from the surrounding living bone, ultimately, forming theSequestrum.
  • When periosteal stripping occurs, the resulting periosteal reaction produces a shell of new bone; the Involucrum, around the dead bone.

Associated conditions

  • 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 often affected.

Gross Pathology

Osteomyelitis in cancer.
Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology.


Microscopic Pathology

{{#ev:youtube|KTfOwYS1ykY}}

References

  1. 1.0 1.1 Gristina AG, Oga M, Webb LX, Hobgood CD (1985). "Adherent bacterial colonization in the pathogenesis of osteomyelitis". Science. 228 (4702): 990–3. PMID 4001933.
  2. 2.0 2.1 2.2 Clarke SR, Foster SJ (2006). "Surface adhesins of Staphylococcus aureus". Adv. Microb. Physiol. 51: 187–224. doi:10.1016/S0065-2911(06)51004-5. PMID 17010697.
  3. 3.0 3.1 Gristina AG, Costerton JW (1984). "Bacterial adherence and the glycocalyx and their role in musculoskeletal infection". Orthop. Clin. North Am. 15 (3): 517–35. PMID 6472832.
  4. Jansson A, Jansson V, von Liebe A (2009). "[Pediatric osteomyelitis]". Orthopade (in German). 38 (3): 283–94. doi:10.1007/s00132-008-1402-6. PMID 19305968.
  5. Bluestein D, Javaheri A (2008). "Pressure ulcers: prevention, evaluation, and management". Am Fam Physician. 78 (10): 1186–94. PMID 19035067.
  6. van Asten SA, La Fontaine J, Peters EJ, Bhavan K, Kim PJ, Lavery LA (2016). "The microbiome of diabetic foot osteomyelitis". Eur. J. Clin. Microbiol. Infect. Dis. 35 (2): 293–8. doi:10.1007/s10096-015-2544-1. PMC 4724363. PMID 26670675.
  7. Lau YS, Wang W, Sabokbar A, Simpson H, Nair S, Henderson B, Berendt A, Athanasou NA (2006). "Staphylococcus aureus capsular material promotes osteoclast formation". Injury. 37 Suppl 2: S41–8. doi:10.1016/j.injury.2006.04.008. PMID 16651071.