Osteitis and osteomyelitis are infections of the bone and bone marrow, respectively. Because these terms are often used interchangeably in clinical settings, both conditions will be referred to as osteomyelitis here. Staphylococcus aureus accounts for the majority of acute osteomyelitis cases; however, there are a number of other pathogens associated with this condition. How the pathogen enters the bone determines the type of osteomyelitis: hematogenous and exogenous forms exist. Hematogenous osteomyelitis is caused by seeding from a remote source and is most common among IV drug users and children. Exogenous osteomyelitis is more common in adults and results from direct inoculation through trauma (posttraumatic osteomyelitis) or contiguous spread from infected adjacent tissue (contiguous osteomyelitis due to, e.g., diabetic foot, contaminated prosthetic device). Osteomyelitis may be either acute or chronic and presents with general signs of local inflammation, including swelling, pain, redness, and warmth. Systemic signs, such as fever and chills, are more indicative of an acute infection. Diagnosis of clinically suspected cases is supported via laboratory tests, biopsy, and/or imaging. The treatment of choice for hematogenous osteomyelitis is IV antibiotics. Surgery may be necessary to remove necrotic bone, abscesses, infected foreign bodies, or fistulae. While osteomyelitis in adults often assumes a chronic course and requires prolonged treatment, children typically make a quick and full recovery.
- Osteitis: a general term for inflammation of the bone
- Osteomyelitis: infection of the bone marrow
- Hematogenous osteomyelitis
- Exogenous osteomyelitis: more common in adults 
Epidemiological data refers to the US, unless otherwise specified.
Routes of infection
- Most commonly due to a single pathogen
- Hematogenous dissemination of pathogen
- Exogenous osteomyelitis: usually due to multiple pathogens
- Microbial: highly virulent pathogens
|Most common pathogens causing osteomyelitis|
|Pathogens||Commonly affected groups|
|Staphylococcus aureus (most common cause)|| |
|Pseudomonas aeruginosa|| |
|Pasteurella multocida|| |
|Fungi (e.g., Candida)|| |
- Onset: usually gradual, over several days
- Chief complaint: pain at the site of infection, possibly related to movement
- Possible localized findings: point tenderness, swelling, redness, warmth
- Possible systemic findings: malaise, fever, chills
- Common localization of hematogenous osteomyelitis
Subtypes and variants
- Definition: osteomyelitis of the vertebrae
- Classification: according to the underlying pathogen
- Clinical features
- Assess patient for clinical features and history suggestive of vertebral osteomyelitis
- Blood cultures
- Inflammatory markers (e.g., CRP)
Imaging (if symptom duration ≥ 2 weeks)
- X-ray (anterior-posterior and lateral views): Diagnosis can be inferred based on radiographic findings consistent with vertebral osteomyelitis and positive blood culture.
Contrast-enhanced MRI: the most sensitive diagnostic study for vertebral osteomyelitis
- Disruption of vertebral structure
- CT scan if MRI is not available
- Gallium scan if MRI is contraindicated (metal foreign body implants) to detect sites of infection
- CT-guided needle aspiration biopsy (confirmatory test): culture and histology
- Bed rest and immobilization of the affected vertebral segment (spinal orthosis is required in severe cases)
- Antibiotic treatment (IV administration, for weeks or months)
- mycobacterium tuberculosis is the underlying pathogen : if
- CT-guided catheter drainage of paravertebral abscess
- Psoas abscess: abscess formation in the psoas muscle, causing pain and swelling in this region
- Prevertebral abscess: manifests with neck pain, difficulty swallowing, difficulty breathing, and possible respiratory failure (formation in the cervical spine can be life-threatening → risk of tracheal compression and airway obstruction)
- Vertebral collapse and spinal instability → cord compression → paraplegia
- Complications of tuberculous spondylitis
- Pott paraplegia is primarily a phenomenon of the past (cases have become very rare as a result of improved treatment regimens.)
- Gibbus deformity
- Abscess formation
- Definition: an intraosseous abscess secondary to chronic hematogenous osteomyelitis that appears in immunocompetent children
- Pathophysiology: Pathogens of low virulence may be contained locally in the form of an abscess.
- Localization: most commonly the metaphysis and epiphysis of long bones (especially in the distal femur and proximal tibia)
- Frequently asymptomatic or only mild symptoms
- Treatment: surgical drainage
- Suspect osteomyelitis in patients with focal symptoms (point tenderness) accompanied by nonspecific signs and symptoms of inflammation.
- Initial work-up includes blood cultures, inflammatory markers, and x-ray imaging.
- Rule out possible primary sources of infection and/or sites of dissemination (e.g., dental infection, furuncle, urinary tract infections).
- Inflammatory markers
- Blood cultures: microbiological testing
- Early stages (< 2 weeks of symptoms onset): typically no pathological findings
- Later stages: bone destruction, sequestrum formation,
- MRI: the most sensitive diagnostic study
- Skeletal scintigraphy: visualizes areas of bone with increased bone turnover
- Radionuclide-labeled leukocyte scintigraphy: detects sites of infection or inflammation
- Sonography: to assess soft tissue involvement
Early stages of osteomyelitis are not visible on x-ray.
- Septic arthritis
- (e.g., , )
- (e.g., bone cyst)
The differential diagnoses listed here are not exhaustive.
- Bed rest and immobilization of the affected extremity
- Antibiotic treatment
|Initial empiric antibiotic treatment|
|In children||< 3 months of age|
|> 3 months of age|
|Pathogen-directed IV antibiotics (according to bone biopsy findings)|
|Methicillin-susceptible S. aureus (MSSA)|
|MRSA or S. epidermidis|| |
|Gram-negative pathogens (including Pseudomonas)|
|Secondary osteomyelitis (e.g., prosthetic joints or foreign bodies)||Rifampicin in addition to the antibiotic regimen|
Treatment of osteomyelitis should not be delayed, especially in children. Osteomyelitis can have detrimental effects on bone development, resulting in severe long-term complications.
- Course: recurring/chronic cases
- In children: growth impairment
We list the most important complications. The selection is not exhaustive.
- Quick, full recovery is common in children receiving appropriate antimicrobial treatment → > 95% of cases resolve completely. 
- Acute osteomyelitis in adults often transforms into chronic osteomyelitis.
- Chronic osteomyelitis