Bone and joint infections Flashcards Preview

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Flashcards in Bone and joint infections Deck (19):
1

What is osteomyelitis?

Infection of bone

2

What is the pathogenesis of osteomyelitis?

Haematogenous
- bacteria in the blood seed bone (e.g. endocarditis, infants and children)

Contiguous
- focus - spread from adjacent area of infection

Direct inoculation
- trauma or surgery

3

What are the stages of osteomyelitis?

Stage I Medullary – necrosis medullary contents/endosteal surface (haematogenous)

Stage II Superficial – necrosis limited to exposed surface (contiguous)

Stage III Localised – full thickness cortical sequestation, stable before and after debridement (trauma, stage I/II evolving)

Stage IV Diffuse – extensive, unstable bone

4

What is the clinical presentation of osteomylitis?

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

5

What is the most common causative organism in osteomyelitis?

S. aureus

6

What other organisms commonly cause oseomyelitis?

- Streptococci (e.g. group A, group B)
- Enterococci
- Gram negative bacilli e.g Salmonella spp, Klebsiella spp, Pseudomonas aeruginosa – (in premature babies, intravenous drug users, sickle cell disease)
- Anaerobes
- Mycobacterium tuberculosis, Brucella spp.

7

What is the gold standard diagnostic technique in osteomyelitis?

- cultures and histology of bone biopsy / needle aspirate
- blood cultures positive in 50%
- CRP usually raised, monitor in response to therapy
- Leukocytosis - not diagnostic

8

What is the treatment for osteomyelitis?

- Antimicrobials +/- surgery depending on stage/site
- Give directed antimicrobial therapy guided by causative organism
- Intravenous antimicrobials initially to ensure compliance and optimal bone levels - penetration into bone is low
- clindamycin, ciprofloxacin, vancomycin, ß-lactams and gentamicin achieve acceptable levels in bone
- Flucloxacillin IV – agent of choice for S.aureus OM

9

What is septic arthritis?

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

10

What are the two types of septic arthritis?

- Native (natural) joint infection

- Prosthetic (artificial) joint infection (early/late)

11

What is the pathogenesis of a native joint infection?

- Organisms enter a joint via the blood or trauma.
- Synovial tissue is highly vascular and lacks a basement membrane - facilitating “seeding”
- Cartilage erosion causes joint space narrowing/impaired function
- Predisposing factors: rheumatoid arthritis, trauma, intravenous drug use, immunosuppressive disease

12

What is the pathogenesis of prosthetic joint infection?

- Organisms enter a joint via the blood, during surgery or following wound infection
- Joint prosthesis and cement provide a surface for bacterial attachment
- Polymorph infiltration results in tissue damage instability of the prosthesis
- Predisposing factors: prior surgery at the site of the prosthesis, rheumatoid arthritis, corticosteroid therapy, diabetes mellitus, poor nutritional status, obesity, and extremely advanced age

13

What is the clinical presentation of septic arthritis?

- Joint: pain, swelling, tenderness, redness and limitation of movement
- systemic upset: fever, chills, night sweats
- Duration of symptoms is variable and influenced by site of infection, type of joint (native vs prosthetic) and causative organism

14

Which viruses can cause arthritis?

- Parvovirus B19
- Rubella virus
- Mumps virus

Usually self limiting part of systemic illness.

15

Which organisms are commonly the cause of native joint infections?

- Staphylococcus aureus
- streptococci (A,B,C,G)
- Haemophilus influenzae
- Gram negative bacilli
- Neisseria gonorrhoeae
- Neisseria meningitidis
- Anaerobes
- mycobacteria

16

Which organism are commonly the cause of prosthetic joint infections?

- Staphylococcus aureus
- Coagulase negative
- staphylococci (CoNS)
- streptococci (A,B,C,G)
- Anaerobes: peptostreptococci, peptococci
- enterococci
- Gram negative bacilli
- corynebacteria
- propionibacteria
- Bacillus spp.
- mycobacteria

17

What sort of analysis would be performed on a joint aspirate?

Total white cell count
- (>40 000/mm3 during infection)

Differential WCC
- (>75% polymorphs during infection)

Gram stain
- (35-65% positive)

Crystal examination
- (e.g. gout can mimic infection)

Culture

?PCR
- (for slow growing organisms e.g M. tuberculosis)

18

What is the treatment for a native joint infection?

1. Removal of purulent material - joint drainage/washout

2. Empirical iv antimicrobial therapy if required (wait until microbiological samples have been taken before starting)

3. Directed iv antimicrobial therapy depending on causative organism and susceptibility (e.g. Flucloxacillin for S.aureus)

4. Duration: 2-4 weeks (native joint)

19

What is the treatment for a prosthetic joint infection?

1. Removal of implant or replacement of some elements, washout (early vs late)

2. Empirical iv antimicrobial therapy if required

3. Directed iv antimicrobial therapy depending on causative organism and susceptibility (e.g.

4. Flucloxacillin plus rifampicin for S.aureus PJI or vancomycin IV plus rifampicin for CoNS )

5. Duration: 6 weeks NB. oral switch.

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