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Clinical Pathology > Diseases of the Musculoskeletal System - Bone and Joint Infections (52) > Flashcards

Diseases of the Musculoskeletal System - Bone and Joint Infections (52) Flashcards

1
Q

Heterogenous disease

A

Many different pathogens, anatomical sites, and clinical ages

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2
Q

Infection of bone

A

Osteomyelitis

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3
Q

Is osteomyelitis easy to treat and diagnose?

A

No, surgery is often needed

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4
Q

Pathogenesis

A
  1. Haematogenous
  2. Contiguous-focus
  3. Direct inoculation
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5
Q

Haematogenous

A

Bacteria in the blood seed bone

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6
Q

Examples of haematogenous spread

A

Endocarditis, infection from canular (more common in infants and children)

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7
Q

Contiguous-focus

A

Spread from adjacent area of infection

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8
Q

Examples of contiguous-focus

A

Foot ulcers in a diabetic foot

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9
Q

Direct inoculation

A

Trauma or surgery

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10
Q

Mader classification

A

Stage 1, 2, 3, 4 (not progression)

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11
Q

Stage 1

A

Medullary - confined to medulla, necrosis medullary contents/endosteal surface (haematogenous) caught early

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12
Q

Stage 2

A

Superficial - necrosis limited to exposed surface - periosteum (contiguous)

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13
Q

Stage 3

A

Localised - full thickness destruction of cortical elements, left as an island lacks blood supply - dies, can’t deliver antibiotics (trauma, stage 2/3 evolving)

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14
Q

Stage 3 treatment

A

Surgery to get rid of infected bone, debriding bone of pus and antibiotics

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15
Q

Stage 4

A

Diffuse - extensive major reconstruction required, unstable bone

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16
Q

Clinical presentation

A

Pain, soft tissue swelling, erythema, warmth, localised tenderness, reduced movement of affected limb, systemic upset uncommon (fever, chills, night sweats, rigors)

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17
Q

Type of pain

A

Nocturnal, localised, progressive

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18
Q

Presentation varies with

A

Age, type of infecting organism and location of infection

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19
Q

Example

A

Tibia, superficial, erythema - common in babies, young children

20
Q

Causative organisms

A
  • Staph aureus (60%)
  • Strep A/B
  • Enterococci
  • Gram negative bacilli
  • Anaerobes
  • M. TB, Brucella
21
Q

Examples of Gram negative bacilli

A

Salmonella, Klebsiella, Pseudomonas aeruginosa (premature baresi, IVDU, sick cell)

22
Q

Diagnoses

A

Culture and histology of bone (biopsy/needle aspirate)

23
Q

C-reactive protein

A

Usually raised

24
Q

Therapy

A

IV antimicrobials +/- surgery (avoid empirical)

25
Q

Antibiotics penetrate well in bone

A

Clindamycin (staph cocci/staph aureus), Ciprofloxacin, Vancomycin, B-lactams and Gentamicin

26
Q

Treatment for S.aureus OM

A

Flucloxacillin IV

27
Q

Septic (infective) arthritis

A

Inflammatory reaction in joint space (arthritis) caused by infection, from direct invasion of the joint

28
Q

Classification for direct infection

A

Native (natural) joint infection vs Prosthetic (artificial) joint infection (early/late)

29
Q

Native joint infection, how do pathogens enter?

A

Via blood (haematogenous) or trauma (surgery/injection)

30
Q

Native joint infection, how does it facilitate seeding

A

Synovial tissue highly vascular and lacks a basement membrane

31
Q

Native joint infection, what does cartilage erosion cause?

A

Joint space narrowing, impaired function

32
Q

Native joint infection, predisposing factors

A

Rheumatoid arthritis, trauma, IVDU, immunosuppressive disease

33
Q

Prosthetic joint infection, how do pathogens enter?

A

Via the blood (haetogenous) during surgery/wound infection

34
Q

What provides surface for bacterial attachment in prosthetic joint infection?

A

Joint prosthesis and cement

35
Q

How does infection occur in prosthetic joint?

A

Polymorph infiltration > tissue damage instability of the prosthesis

36
Q

Prosthetic joint infection, predisposing factors

A

Prior surgery at the site of the prosthesis, rheumatoid arthritis, corticosteroid therapy, diabetes mellitus, poor nutritional status, obesity and extremely advanced age

37
Q

Septic arthritis clinical presentation

A

Joint (pain, swelling, tenderness, redness and limitation of movement)

Systemic (fever, chills, night sweats)

38
Q

Duration of septic arthritis clinical presentation

A

Variable, influenced by site of infection, joint type and causative organism

39
Q

Causative organisms of septic joints

A

Bacteria, fungi (Candida), Viruses (Parvovirus B19, Rubella virus, Mumps virus - self limiting)

40
Q

Native joint causative organisms

A

Staph aureus, Strep (A,B,C,G), gram neg bacilli, H.influenzae, N.gonorrhoeae, N.meningitidis, anaerobes, mycobacteria

41
Q

Prosthetic joint infection

A

Staph. aureus, coagulase negative staph, enterococci, strep (A,B,C,G), anaerobes (peptostreptococci, peptococci), enterococci, gram negative bacilli, coryne bacteria, propionibacteria, bacillus, mycobacteria

42
Q

Examine joint aspirate

A

WCC (>40,000), Differential WCC (>75%), gram stain (35-65% positive), crystal examination (gout can mimic infection), culture, PCR (slow growing organisms - M.TB)

43
Q

Therapy for native joint infection

A
  • Removal of pus - joint drainage washout
  • Empirical IV antimicrobial
  • Directed IV antimicrobial
  • Duration 2-4 weeks
44
Q

Therapy for prosthetic joint infection

A
  • Removal of implant/replacement of some of elements (wash out)
  • Empirical IV antimicrobial
  • Directed IV antimicrobial
  • Duration 6 weeks
45
Q

Antibiotics for PJI

A

Flucloxacillin plus rifampicin for S.aureus

Clinical Pathology (60 decks)

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