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.
Educate patients regarding disease state and drug therapy.
KEY CONCEPT Osteomyelitis is an infection of the bone that can be an acute or chronic process. The inflammatory response associated with acute osteomyelitis can lead to bone necrosis and subsequently chronic infections.1 Bacterial pathogens, particularly Staphylococcus aureus, are the most common microorganisms implicated in these infections.1,2,3,4,5,6,7,8 Diagnosis and treatment are often difficult due to the heterogeneous nature of osteomyelitis.1,2 Medical management is the mainstay of treatment for acute infections; however, surgical intervention is necessary for chronic infections that involve bone necrosis.1,2 Outcomes may vary based on patient-specific risk factors, duration of disease, and site of infection.1,2
KEY CONCEPT Osteomyelitis is most often classified by duration of disease and route of infection.1,2,9 Historically, osteomyelitis has been classified as acute or chronic based on duration of disease.1,2,9 However, there are no established definitions for acute and chronic infections.1,9,10 Acute infection has been defined as first episode or recent onset of symptoms (within 2 weeks).2,9,10,11 Chronic osteomyelitis is generally defined as relapse of the disease or symptoms persisting beyond 2 months.2,9 Because there is no abrupt demarcation, but rather a gradual shift from acute to chronic infection, others describe chronic osteomyelitis as the presence of necrotic bone.1,2,10,11
In the Waldvogel classification scheme, the route of infection is categorized as either hematogenous or contiguous.9 Osteomyelitis secondary to a contiguous focus is further subdivided into infections with or without vascular insufficiency. Typical bone involvement in osteomyelitis depends on the route of infection.
Hematogenous: long bones (femur, tibia) in children and vertebra in the elderly2,3,4,5,10
Contiguous with vascular insufficiency: lower extremities2,11,12
Contiguous without vascular insufficiency: bones affected by trauma, surgery, or adjacent to soft-tissue infection1,5
A single pathogen is most often isolated in hematogenous osteomyelitis, whereas multiple organisms are often isolated in contiguous osteomyelitis.7,10,11,13
EPIDEMIOLOGY AND ETIOLOGY