Osteomyelitis Flashcards
What is osteomyelitis?
An infection of the bone
What bones are principally affected in osteomyelitis?
Long bones, with tiba > fibia > humerus
What can osteomyelitis be divided into?
- Acute
- Subacute (2-3 weeks)
- Chronic
Where in the bone is infection usually seen in osteomyelitis?
In the metaphyseal region of bones
How does infection get to the bone in osteomyelitis?
- Haematogenous route
- Direct inoculation
- Local extension from adjacent sites
Where does the infection come from when it is spread via haematogenous route in osteomyelitis?
Most infections are spread from a site of entry, e.g. respiratory, GI, ENT, or skin sites
What might cause direct inoculation of infection causing osteomyelitis?
- Open fractures
- Penetrating wounds
When can infection spread to the adjacent joint?
In the infant
Why can infection spread to the adjacent joint in the infant?
Because the transphyseal vessels are patent
How does infection tend to spread in adolescents?
Through the medullary canal
Can organisms be isolated on testing in osteomyelitis?
Not always
Why can organisms not always be isolated in osteomyelitis?
The yield for bacterial growth from synovial fluid and bone aspirate is small
What is the most common bacteria causing osteomyelitis in all age groups?
S. Aureus
What other organisms can cause osteomyelitis in neonates?
- Group B streptococcus
- Gram -ve enteric bacilli
What other organisms can cause osteomyelitis in <2 years?
Haemophilus influenzae
What other organisms can cause osteomyelitis in >2 years?
- Gram +ve cocci
- Pseudomonas aeruginosa
What other organisms can cause osteomyelitis in adolescents?
Neisseria gonorrhoeae
What are the risk factors for osteomyelitis?
- Infant
- Male
What % of cases of osteomyelitis occur in the first 2 years?
33%
How does the presentation of osteomyelitis differ in infants compared to older children?
The presentation is more insidious in infants, in whom swelling or reduced limb movement is the initial sign
How does osteomyelitis present in older children?
- Pain
- Limping
- Refusal to walk/weight bear
- Fever
- Malaise
- Flu-like symptoms
- Overlying bone tenderness, with or without swelling
What might occur in the adjacent joint in osteomyelitis?
Sterile effusion
What investigations should be done in osteomyelitis?
- Bloods
- X-ray affected bone
- US-guided aspiration
- MRI
- Open biopsy may be necessary
What bloods should be done in osteomyelitis?
- FBC
- ESR
- CRP
- Blood cultures
In what % of cases of osteomyelitis are blood cultures positive?
50%
What might be found on x-ray of bone in the early stages of osteomyelitis?
May be normal, possibly with soft tissue oedema visible
What might be found on x-ray of bone in late stages of osteomyelitis?
Metaphyseal rarefaction
When do destructive changes in bone appear on x-ray in osteomyelitis?
After 10 days
What is the purpose of US-guided aspiration in osteomyelitis?
For microscopy and culture
What is the purpose of MRI in osteomyelitis?
Soft tissue assessment
What might be found on MRI soft tissue assessment in osteomyelitis?
- Bone marrow involvement
- Abscess formation
- Joint effusion
- Subperisoteal extension
What are the differential diagnoses of osteomyelitis?
- Septic arthritis
- Osteosarcoma
- Trauma or fracture
- Rheumatoid disease
- Toxic synovitis
What is involved in the medical management of osteomyelitis?
IV antibiotics for a minimum of 2 weeks, or until clinical recovery with acute-phase reactants normalising, followed by oral antibiotics for 4 weeks
What is required when deciding on antibiotics for osteomyelitis?
Early liason with microbiologist
What are the surgical options in the management of osteomyelitis?
- Aspiration or surgical decompression of subperiosteal space
- Surgical drainage
When might aspiration or surgical decompression of the subperiosteal space be performed?
If the presentation is atypical, or in immunodeficient children
When is surgical drainage performed in osteomyelitis?
If the condition does not respond rapidly to antibiotic therapy
What is done to the limb in osteomyelitis, in terms of mobilisation?
The affected limb is usually rested in a splint, then mobilised
What are the potential complications of osteomyelitis?
- Sepsis
- Pathological fractures
- Sequesteration
- Growth disturbance
