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Osteomyelitis

Last updated: February 16, 2021

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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
    • Acute form: develops within days or weeks
    • Chronic form: develops slowly (over months or years) and is associated with avascular bone necrosis and sequestrum formation (necrotic bone fragment that has become detached from the original bone)
  • Hematogenous osteomyelitis
    • More common in children and adolescents (> 50% of cases occur in children ≤ 5 years) [1]
    • Vertebral osteomyelitis (a form of hematogenous osteomyelitis) occurs mainly in adults aged > 50 years [2]
  • Exogenous osteomyelitis: more common in adults [3]

Epidemiological data refers to the US, unless otherwise specified.

Routes of infection

  • Hematogenous osteomyelitis
    • Most commonly due to a single pathogen
    • Hematogenous dissemination of pathogen
  • Exogenous osteomyelitis: usually due to multiple pathogens
    • Posttraumatic: infection following deep injury (penetrating injury, open fractures, severe soft tissue injury)
    • Contiguous: spread of infection from adjacent tissue
      • Secondary to infected foot ulcer in diabetic patients
      • Iatrogenic (e.g., postoperative infection of a prosthetic joint implant)

Risk factors

Pathogens

Most common pathogens causing osteomyelitis
Pathogens Commonly affected groups
Staphylococcus aureus (most common cause)
  • Children and adults
  • Individuals that recreationally use IV drugs [4]
  • Patients with vertebral lesions
  • Patients with prosthetics [5]
Staphylococcus epidermidis
Streptococci
Pseudomonas aeruginosa
  • IV drug users [6]
  • Plantar puncture wounds (especially if wearing rubber-soled footwear)
Enterobacteriaceae Salmonella
Klebsiella
  • Patients with UTIs
Mycobacterium tuberculosis
Pasteurella multocida
  • Bites from dogs and cats
Fungi (e.g., Candida)

Acute osteomyelitis

Chronic osteomyelitis

  • Onset
    • Usually following a prior episode of osteomyelitis
    • May last for months
  • Chief complaint: recurrent pain
  • Possible findings
    • Swelling, redness
    • Local sinus tract formation, perhaps draining pus

Vertebral osteomyelitis [7]

Brodie abscess

  • Definition: subacute osteomyelitis characterized by an intraosseous abscess; commonly affects the distal femur and proximal tibia
  • Pathophysiology: hematogenous seeding of a distant infectious focus → subacute or chronic pyogenic infection of the bone → fibrous and granulation tissue formation around pyogenic focus → localized abscess
  • Clinical features
    • Frequently asymptomatic or only mild symptoms
    • Localized pain
  • Diagnostics: well-circumscribed, thick-walled cystic lesion in the metaphysis and epiphysis of long bones on x-ray and contrast-enhanced MRI
  • Treatment: surgical drainage

Clinical approach

Laboratory tests

Imaging

Early stages of osteomyelitis are not visible on x-ray.

Biopsy (confirmatory test)

The differential diagnoses listed here are not exhaustive.

Conservative

  • Bed rest and immobilization of the affected extremity
  • Antibiotic treatment
Initial empiric antibiotic treatment
Patient group Regimen
In adults
In children < 3 months of age
> 3 months of age
Pathogen-directed IV antibiotics (according to bone biopsy findings)
Pathogen Regimen
Methicillin-susceptible S. aureus (MSSA)
MRSA or S. epidermidis
Gram-negative pathogens (including Pseudomonas)
Special cases
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.

Surgical

We list the most important complications. The selection is not exhaustive.

  • Acute osteomyelitis
    • Quick, full recovery is common in children receiving appropriate antimicrobial treatment → > 95% of cases resolve completely. [10]
    • Acute osteomyelitis in adults often transforms into chronic osteomyelitis.
  • Chronic osteomyelitis
    • Difficult to cure
    • Often requires repeated surgical and antibiotic treatment (over years to decades)
    • In patients with diabetes or vascular insufficiency, the probability of complete resolution is particularly low.
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  2. Sapico FL, Montgomerie JZ. Pyogenic Vertebral Osteomyelitis: Report of Nine Cases and Review of the Literature. Clinical Infectious Diseases. 1979; 1 (5): p.754-776. doi: 10.1093/clinids/1.5.754 . | Open in Read by QxMD
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  6. Pseudomonas aeruginosa. http://www.antimicrobe.org/new/b112.asp. . Accessed: December 15, 2016.
  7. Berbari EF, Kanj SS, et al. 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. Clin Infect Dis. 2015; 61 (6): p.e26-e46. doi: 10.1093/cid/civ482 . | Open in Read by QxMD
  8. Töpel I, Zorger N, Steinbauer M. Inflammatory diseases of the aorta. Gefässchirurgie. 2016; 21 (S2): p.87-93. doi: 10.1007/s00772-016-0142-x . | Open in Read by QxMD
  9. Fritz JM, McDonald JR. Osteomyelitis: approach to diagnosis and treatment.. Phys Sportsmed. 2008; 36 (1): p.nihpa116823. doi: 10.3810/psm.2008.12.11 . | Open in Read by QxMD
  10. Le Saux N, Howard A, Barrowman NJ, Gaboury I, Sampson M, Moher D. Shorter courses of parenteral antibiotic therapy do not appear to influence response rates for children with acute hematogenous osteomyelitis: a systematic review.. BMC Infect Dis. 2002; 2 : p.16. doi: 10.1186/1471-2334-2-16 . | Open in Read by QxMD