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

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

Flashcards in Diseases of the Musculoskeletal System - Bone and Joint Infections (52) Deck (45):
1

Heterogenous disease

Many different pathogens, anatomical sites, and clinical ages

2

Infection of bone

Osteomyelitis

3

Is osteomyelitis easy to treat and diagnose?

No, surgery is often needed

4

Pathogenesis

1. Haematogenous
2. Contiguous-focus
3. Direct inoculation

5

Haematogenous

Bacteria in the blood seed bone

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Examples of haematogenous spread

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

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Contiguous-focus

Spread from adjacent area of infection

8

Examples of contiguous-focus

Foot ulcers in a diabetic foot

9

Direct inoculation

Trauma or surgery

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Mader classification

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

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Stage 1

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

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Stage 2

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

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Stage 3

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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Stage 3 treatment

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

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Stage 4

Diffuse - extensive major reconstruction required, unstable bone

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Clinical presentation

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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Type of pain

Nocturnal, localised, progressive

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Presentation varies with

Age, type of infecting organism and location of infection

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Example

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

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Causative organisms

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

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Examples of Gram negative bacilli

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

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Diagnoses

Culture and histology of bone (biopsy/needle aspirate)

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C-reactive protein

Usually raised

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Therapy

IV antimicrobials +/- surgery (avoid empirical)

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Antibiotics penetrate well in bone

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

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Treatment for S.aureus OM

Flucloxacillin IV

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Septic (infective) arthritis

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

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Classification for direct infection

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

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Native joint infection, how do pathogens enter?

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

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Native joint infection, how does it facilitate seeding

Synovial tissue highly vascular and lacks a basement membrane

31

Native joint infection, what does cartilage erosion cause?

Joint space narrowing, impaired function

32

Native joint infection, predisposing factors

Rheumatoid arthritis, trauma, IVDU, immunosuppressive disease

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Prosthetic joint infection, how do pathogens enter?

Via the blood (haetogenous) during surgery/wound infection

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What provides surface for bacterial attachment in prosthetic joint infection?

Joint prosthesis and cement

35

How does infection occur in prosthetic joint?

Polymorph infiltration > tissue damage instability of the prosthesis

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Prosthetic joint infection, predisposing factors

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

37

Septic arthritis clinical presentation

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

Systemic (fever, chills, night sweats)

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Duration of septic arthritis clinical presentation

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

39

Causative organisms of septic joints

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

40

Native joint causative organisms

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

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Prosthetic joint infection

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

42

Examine joint aspirate

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

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Therapy for native joint infection

- Removal of pus - joint drainage washout
- Empirical IV antimicrobial
- Directed IV antimicrobial
- Duration 2-4 weeks

44

Therapy for prosthetic joint infection

- Removal of implant/replacement of some of elements (wash out)
- Empirical IV antimicrobial
- Directed IV antimicrobial
- Duration 6 weeks

45

Antibiotics for PJI

Flucloxacillin plus rifampicin for S.aureus

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