Bone & Soft TIssue Infections Flashcards
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)
How might acute OM present in a child?
- Severe pain
- Reluctant to move (neighboring joint flexed, no weight bearing, +/- tenderness)
- fever (swinging pyrexia) and tachycardia
- Systemic Symptoms e.g. fatigue, malaise & N&V
- Toxaemia
How might acute primary OM present in an Adult?
Mostly in the thoracolumbar spine
* backache
* Hx UTI or urological procedure
Esp. in the elderly, diabetic or immunocompromised
Which joint/s does acute primary OM commonly affect in adults?
Thoracolumbar spine
Which of primary or secondary acute OM affects adults more commonly?
Secondary acute OM
How might acute secondary OM present in an adult?
More common
* Post an open fracture or surgery
Mix of organisms
What tests could we do to diagnose OM?
FBC
Differential WCC
U&Es
3x Blood cultures
MRI
X-ray
Bone biopsy
ESR & CRP
Also Aspiration, US, ISotope bone scan and labelled WC scan
And swabs from site during implantation surgery
What would appear on an acute OM Diff. WCC?
Neutrophilic Leucocytosis
What would appear on an Acute OM X-ray?
nothing in first 2 wks
10-20 days you get Early periosteal changes
Then you get late bone necrosis (Sequestrum) and LAte periosteal growth (Involucrum)
DDX for Acute OM?
Acute Septic Arthrits (more common)
Acute Inflammatory Arthritis
Trauma
Transient Synovitis
Soft Tissue Infection (e.g. erysipelas or Cellulitis)
Rarely sickle cell, rheumatic fever, necrotising fasciitis or Gaucher’s Disease
Treatment for Acute OM?
Supportive Care
Rest & Splintage
Abx
Surgery
Whats included in supportive care for acute OM?
Fluids
Analgesia
What Abx are used for Acute OM?
Empircally Flucloxacillin & Benzylpenicillin
4-6 wks on an IV/oral switch at 7-10 days
When would we perform surgery for Acute OM?
Refractory to Abx after 48 hours
Debride dead/infected tissue
Drain abscess
Aspirate abscess for culture
What surgical treatments do we have for Acute OM?
Drainage
Lavage
Infected joint replacement
Complications of Acute OM?
Think spread of infection:
- Septicaemia
- Metastatic infection
- Septic Arthritis
Think damage to bone:
- Pathological fracture
- Growth abnormality
Also Chronic OM
How can Chronic OM originate?
Acute OM
De-novo (IVDA or ops in the elderly, immunosuppressed or diabetic)
repeated breakdown of ‘healed’ wounds
What organisms cause Chronic OM?
1) Staph Aureus
2) E. Coli
3) Strep Pyogenes
4) Proteus
5) TB
Complications of Chronic OM?
Metastatic Infection
Pathological fracture
Abnormal growth and deformity
Chronically discharging sinuses
SCC
Treatment for Chronic OM?
Long Term Abx
Surgery
~Amputation
What is the main causative organisms of Acute OM in adults?
Staph Aureus
Kids can get H influenzae and strep pyogenes
Causative organisms of Acute OM in adults?
Adults can get:
- Coagulase -ve staph from prosthetics
- TB
- Pseudomonas from IVDA & Penetrating foot injury
Staph Aureus is still the main cause
What is the source of acute OM infection in adults?
- UTI
- Arterial lines
