Bone & Soft TIssue Infections Flashcards
(46 cards)
This deck covers:
Acute & Chronic Osteomyelitis
Septic Arthritis
TB
What are the risk factors for acute osteomyelitis?
Diabetes mellitus
Peripheral vascular disease
Malnutrition
Immunosuppression
Malignancy
Extremes of age
Local factors e.g chronic lymphedema, vasculitis, neuropathy etc.
Who suffers from acute osteomyelitis?
Mostly kids, and generally boys with a trauma history
Others:
Adults with another disease:
* DM
* RA
* Immune compromise
* Long-term steroid treatment
* Sickle cell
What are the different sources for infection in acute OM infection?
- Haematogenous: from bacteremia (commonly affects kids & elderly)
- Non-hematogenous: local spread from trauma (open farcture) & surgery, joint replacement
- 2ndry to vascular insufficiency
- Infants: infected umbilical cord
- Children: boils, tonsilitis, skin abrasions
- Adults: UTI, arterial lines
What is a common source of infection for OM in the elderly and kids?
Haematogenous (bacteremia)
What is the source of acute OM infection in children?
- Boils
- Tonsilitis
- Skin abrasions
What is the source of acute OM infection in adults?
- UTI
- Arterial lines
What is a non-hematogenous source of acute OM infection?
Local spread from the contiguous site of infection:
* Trauma (open farcture)
* Bone surgery (ORIF)
* Joint replacements
What is the source of acute OM infection in infants?
Umbilical cord infection
What organism is the main cause of OM
1) Staph Aureus
It’s the biggest cause in any patient group. However certain groups (e.g. by age, co-morbidity or immunocompromise) are at risk of other specific organisms
What organisms cause acute OM in infants <1yr?
1) Staph Aureus
2) Group B Strep
3) E. Coli (most common if under <1month old)
What organisms cause acute OM in older children?
- Staph aureus
*Strep pyogenes - Haemophilus Influenza (immunization sig. reduced)
What organisms cause acute OM in adults?
- Staph aureus
- Mycobacterium tuberculosis
- Pseudomonas aeroginosa (esp. secondary to penetrating foot injuries, IVDAs)
- Coagulase negative staphylococci (prostheses)
- Propionibacterium spp (prostheses)
What organisms commonly cause acute OM infections in adults, with penetrating foot injuries or IVDAs?
Pseudomonas aeroginosa
What organisms commonly cause acute OM infection in pts with prosthesis?
- Coagulase negative staphylococci (prostheses)
- Propionibacterium spp (prostheses)
What organisms cause OM in diabetics?
Staph Aureus
Mixed infection incl. Anaerobes
What organisms cause OM in Sickle Cell patients?
Staph Aureus
Salmonella
What organisms cause OM in HIV/AIDS patients?
Staph Aureus
Candida
Where in the bone is acute OM likely to arise?
The metaphysis of long bones:
* Distal femur
* Proximal tibia
*Proximal humerus
or
Joints with an intra-articular metaphysis e.g. hip/elbow (this can lead to septic arthritis or arise from SA)
Describe the pathogenesis of acute OM?
The infection starts at the metaphysis of bone
-> Vascular stasis (venous congestion +artehrial thrombosis)
-> Acute inflammation causes an increase in pressure
-> Suppuration
-> Pressure released into joint (medulla, sub-periosteal or into joint)
-> Necrosis of bone (sequestrum)
-> New Bone growth (involucrum)
-> Resolves or Chronic
What do we call necrosed bone?
Sequestrum
What do we call new bone growth?
Involucrum
How might acute OM present in an infant?
- Failure to thrive
- +/-drowsy or irritable
- Decreased range of movement or an odd position
- Tenderness & swelling over metaphysis
Mostly in the knee
What joint does acute OM affect in infants?
Knee joint (often multiple sites)
