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MSK > Bone & Soft TIssue Infections > Flashcards

Bone & Soft TIssue Infections Flashcards

1
Q

This deck covers:

A

Acute & Chronic Osteomyelitis
Septic Arthritis
TB

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2
Q

Who suffers from osteomyelitis?

A

Mostly kids, and generally boys with a trauma history

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3
Q

What are the common sources of OM infection [3]

A

Haematogenous:

  • Infected Umbilical Cord in infants
  • Boils/tonsilitis/skin abrasions in kids
  • UTIs & arterial lines in adults

Local: open #

2* to vascular insufficiency

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4
Q

What organisms cause OM in infants <1yr? [3]

A

1) Staph Aureus
2) Group B Strep
3) E. Coli (most common if under <1month old)

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5
Q

What organisms cause OM in Older kids? [3]

A

1) Staph Aureus
2) Strep Pyogenes
3) H. Influenzae

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6
Q

What organisms cause OM in Adults? [4]

A

1) Staph Aureus
2) Coagulase -ve Staph via prosthesis
3) Mycobacterium TB
4) Pseudomonas Aeruginosa via penetrating foot injury or IVDA

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7
Q

What organisms cause OM in diabetics?

A

Pseudomonas

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8
Q

What organisms cause OM in Sickle Cell patients?

A

Salmonella

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9
Q

What organisms cause OM in people with dead fish contact? (Fishermen and filleters)

A

Mycobacterium Marinum

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10
Q

What organisms cause OM in HIV/AIDS patients?

A

Candida

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11
Q

Where in the bone is OM likely to arise? [2]

A

The metaphysis of long bones or joints with an intra-articular metaphysis e.g. hip/elbow (this can lead to septic arthritis or arise from SA)

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12
Q

Describe the pathogenesis of OM [5]

A
  • venous congestion and venous thrombosis
  • active inflammation and increased pressure results in…
  • Suppuration which releases pressure and pus into medulla/joint
  • Sequestrum is bone necrosis
  • Involcrum - bone formation replaces necrosis with
  • either resolution or chronic OM
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13
Q

How might OM present in an infant? [5]

A 
Failure to thrive
~drowsy or irritable
Decreased movement or an odd position
Tenderness &amp; swelling over metaphysis
Mostly in the knee
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14
Q

How might OM present in a child? [4]

A

Severe pain +/- tenderness, fever and tachycardia
Systemic Symptoms e.g. fatigue, malaise & N&V

They won’t move or weight bear on that bone

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15
Q

How might primary OM present in an Adult? [3]

A

Mostly in the thoracolumbar spine
So backache with a h/o UTI or urological procedure
Esp. in the elderly, diabetic or immunocompromised

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16
Q

How might secondary OM present in an adult?

A

Post open fracture or surgery

17
Q

What tests could we do to diagnose OM? [8]

Indicate gold standard with *

A 
Lab work
Bone biopsy
Tissue swabs 
Imaging
USS
Aspiration
Isotope bone scan
MRI*
18
Q

What would appear on an acute OM Diff. WCC?

Describe how blood cultures should be done in acute OM?

In prosthetic infections, how many tissue swabs must be done around implant at debridement?

A

Neutrophilic Leucocytosis

Blood cultures should be done at pyrexial peak as the most bugs are released into circulation at this point
3 must be done

Prostethic infections: Max 5 sites

19
Q

What would appear on an Acute OM X-ray? [4]

Early radiographs of acute OM will show minimal changes. What range of dates is this?

A

Periosteal changes
Medullary changes with lytic areas
Late osteonecrosis
Periosteal new bone - involucrum

10-14days

20
Q

DDX for Acute OM? [5]

Rare causes [4]

A

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

21
Q

Treatment for Acute OM? [4]

A

Supportive Care
Rest & Splintage
Abx
Surgery

22
Q

Whats included in supportive care for acute OM? [2]

A

Fluids

Analgesia

23
Q

What Abx are used for Acute OM? [3]

What antibiotic to use for pseudomonas?

A

6w abx total
Empirical IV FLUCLOXICILLIN then switch to oral after 7-10d (ESR should return to normal in 4-6w)

Pseudomonas: CIPROFLOXACIN

24
Q

When would we perform surgery for Acute OM? [4]

A

Refractory to Abx after 48 hours
Debride dead/infected tissue
Drain abscess
Aspirate abscess for culture

25
Q

What surgical treatments do we have for Acute OM? [3]

A

Drainage
Lavage
Infected joint replacement

26
Q

Complications of Acute OM? [6]

A

Think spread of infection:

  • Septicaemia
  • Metastatic infection
  • Septic Arthritis

Think damage to bone:

  • Pathological fracture
  • Growth abnormality

Also Chronic OM

27
Q

How can Chronic OM originate? [2]

A

Acute OM
De-novo (IVDA or ops in the elderly, immunosuppressed or diabetic)
repeated breakdown of ‘healed’ wounds

28
Q

What organisms cause Chronic OM? [5]

A

1) Staph Aureus
2) E. Coli
3) Strep Pyogenes
4) Proteus
5) TB

29
Q

Complications of Chronic OM? [6]

A 
Amyloid
Metastatic Infection
Pathological fracture
Abnormal growth and deformity
Chronically discharging sinuses
SCC in sinus track
30
Q

Treatment for Chronic OM [4]

A
  • radical excision of sequestra
  • skeletal stabilisation
  • dead space mx (plastics input)
  • abx (as acute) for >12w
31
Q

Septic arthritis
Ep
Ax [5]

A

Ep: neonate, child or immunocompromised adult
Ax: staph aureus, Neisseria gonorrhoea, haemophilus influenza, strep pyogenes, E. coli

32
Q

Septic arthritis

Pathophysiology: source [3], process [4], sequelae [3]

A
  • Source: direct invasion (penetrating wound, arthroscopic), bone abscess eruption, haematogenous
  • Process: acute synovitis with purulent joint effusion and articular cartilage attacked by bacterial toxin and cellular enzymes
  • Sequelae: destruction of articular cartilage causing OA, complete recovery, fibrous or bony ankyloses
33
Q

Septic arthritis

What diagnostic criteria is used, what are the 4 components?

A

• Kocher diagnostic criteria: >38.5oC, NWB, raised ESR and WCC

34
Q

Septic arthritis presentation
Neonate
Child [3]
Adult

A

• Neonate: sepsis
• Child:
- acute pain in single large joint
- reluctance for any large joint movement
- tachycardia, pyrexia, increased tenderness
• Adult: usually infected joint replacement of superficial joint e.g. knee, ankle, wrist

35
Q

SA Ix [6]

A
  • Bloods: RBC (leucocytosis), elevated ESR and CRP, blood cultures
  • Synovial fluid aspiration: MC&S
  • Imaging: XR (few early changes but may show underlying osteomyelitis), CT/MRI if dx doubt
36
Q

SA Mx [3]

What is a complication of SA?

A

• 6-12w abx: FLUCLOXACILLIN
• Surgery:
- repeated needle aspiration for decompression
+/- lavage if deep joint or refractory to medical mx

Complication: secondary OA

37
Q

What can be seen on ultrasound in acute OM

A

Pus collection in periosteum

38
Q

7 reasons for failure of ab

A 
Drug resistance
Bacterial persistence
Poor host defenses
Poor drug absorption
Drug inactivation by host flora
Poor bone penetration
MRSA
39
Q

Acute septic arthritis
Why does SA require shorter course than chronic OM
3-4 weeks vs 4-6 weeks?

A

Joint responds better than bone to antibiotics

MSK (28 decks)

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