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LEARNING OBJECTIVES
Upon completion of the chapter, the reader will be able to:
List common risk factors for osteomyelitis.
Discuss the pathophysiology of osteomyelitis.
Compare and contrast the classic signs and symptoms of acute and chronic osteomyelitis.
Evaluate microbiology culture data and other laboratory tests and imaging studies utilized for diagnosis of osteomyelitis.
List the most common pathogens isolated in acute and chronic osteomyelitis.
Develop a treatment plan for osteomyelitis.
Recommend parameters to monitor antimicrobial therapy for effectiveness and toxicity.
Describe how principles of antimicrobial stewardship can be applied to the management of osteomyelitis.
Educate patients regarding lifestyle modifications that may impact disease outcomes.
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Osteomyelitis is an infection of the bone that may be either an acute or chronic process. The inflammatory response associated with acute osteomyelitis can lead to bone necrosis and subsequent chronic infection.1 Bacterial pathogens, such as Staphylococcus aureus, are most commonly responsible for both acute and chronic infections.1-8 Diagnosis and treatment present significant challenges to clinicians due to the complex nature of osteomyelitis.1,2 Medical management is considered the cornerstone of treatment for acute infections; however, surgical intervention in addition to antimicrobial therapy is necessary to achieve cure for chronic infections.1,2
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Osteomyelitis is most often classified by duration of disease and route of infection.1,2,9
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Two major osteomyelitis classification schemes exist. The Cierny–Mader classification focuses on the affected portion of bone, physiologic status of the patient, and factors impacting local vascularity.1 In contrast, the Waldvogel classification scheme categorizes disease based on route of infection (hematogenous or contiguous) and duration of disease (acute versus chronic).9 Using this classification scheme, osteomyelitis secondary to a contiguous focus can be further subdivided into infections with or without vascular insufficiency. Typical bone involvement in osteomyelitis depends on the route of infection.
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Hematogenous: long bones (femur, tibia) in children and vertebra in the elderly2–5,10
Contiguous with vascular insufficiency: lower extremities2,11,12
Contiguous without vascular insufficiency: bones affected by trauma, surgery, or adjacent soft-tissue infection1,5
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A single pathogen is most often isolated in hematogenous osteomyelitis, whereas multiple organisms are often isolated in contiguous infections.7,10,11,13
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While there are no validated definitions delineating acute versus chronic infection,1,9,10 acute infection is often defined as the first episode or onset of symptoms within 2 weeks.2,9-11 In comparison, chronic osteomyelitis is generally defined as disease relapse or symptoms persisting beyond 2 months.2,9 Because there is no abrupt temporal demarcation, but rather a gradual shift from acute to chronic infection, many describe chronic osteomyelitis as the presence of necrotic bone.1,2,10,11