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Pathology > Mi - Wound, Bone & Joint Infections > Flashcards

Mi - Wound, Bone & Joint Infections Flashcards

1
Q

incidence of septic arthritis

A

2 to 10 per 100,000

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2
Q

in whom is septic arthritis more common

A

RA patients (28-38 per 100,000)

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3
Q

mortality and morbidity of septic arthritis

A

mortality = 7-15%
morbidity = 50%

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4
Q

Rfs of septic arthritis

A

RA
osteoarthritis
joint prosthesis
IVDU
DM, chronic renal disease, chronic liver disease
steroids / immunosuppression
trauma - intra-articular or penetrating injury

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5
Q

pathophysiology of septic arthritis

A

organisms adhere to synovium
bacterial proliferation in synovial fluid –> host inflamm response –> joint damage –> exposure of host derived protein (eg fibronectin) to which bacteria adhere

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6
Q

bacterial factors of septic arthritis pathogenesis

A

s.aureus has fibronectin binding protein receptors that recognise slected host proteins
s.aureus (some strains) also produce cytotoxin PVL –> fulminant infection
kingella kingae synovial adherence is via bacterial pilli

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7
Q

host factors for septic arthritis pathogenesis

A

leucocyte derived proteases and cytokines lead to cartilage degradation / bone loss
raised intra articular pressure impedes capillary blood flow –> cartilage and bone ischaemia /necrosis
genetic deletion of macrophage derived cytokines –> reduced host-response in S.aureus sepsis
absence of IL10 increase severity of staph joint disease

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8
Q

common causative organisms of septic arthritis

& less common causes

A

STAPH AUREUS no1
strep - pyogenes, pneumoniae, agalactiae
some gram negatives

less common
- lyme disease
- brucellosis
- mycobacteria
- fungi

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9
Q

clinical features of septic arthritis

A

1-2 wk history of red /swollen joint, restricted movement
monoarticular (90%) - usually knee (50%)

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10
Q

Ix for septic arthritis

A

blood culture if pyrexial
synovial fluid aspiration for MCS - can be USS guided
ESR, CRP
CT / MRI

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11
Q

synovial count cut off for septic arthritis diagnosis

A

> 50,000 WBC/mL

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12
Q

Mx of septic arthritis

A

ABx - IV cephlasporin / fluclox
+/- vancomycin if MRSA
IV for 2 weeks then oral for up to 4 weeks
arthroscopic washout

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13
Q

cause of vertebral osteomyelitis

A

acute haematogenous
exogenous - after disc surgery / implant assoicated

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14
Q

causative organisms of vertebral osteomyelitis

A

s.aureus #1
coagulase neg staphylcoccus
gram neg rods
streptococci

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15
Q

most common site of infection of vertebral osteomyelitis

A

lumbar
cervical

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16
Q

sx of vertebral osteomyelitis

A

back pain
fever
neuro impairment if cord compression

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17
Q

Dx of vertebral osteomyelitis

A

MRI - 90% sensitive
blood cultures
CT / open biopsy

18
Q

Tx of vertebral osteomyelitis

A

6 weeks of ABx
- longer if undrained collections / implant associated
surgery if spinal cord compression

19
Q

Sx of chronic osteomyelitis

A

pain
brodies abscess
sinus tract

20
Q

Dx of chronic osteomyelitis

A

MRI
bone biopsy - culture and histology

21
Q

Tx of chronic osteomyelitis

A

masquelet technique
oral ABx (up to 6 weeks)

22
Q

what is masquelet technique

A
  • radical sequestrectomy
  • removal of foreign bodies, filling the defect with ABx loaded cement spacer and external fixation
  • in 6 to 8 weeks, remove cement, fill defect with autologous bone graft
23
Q

Sx of prosthetic joint infection

A

pain around joint
patient complains joint was never right
early failure
discharging sinus tract

24
Q

causative organisms of prosthetic joint infection

A

gram positive cocci
staph aureus
less common is gram neg

25
Q

Dx of prosthetic joint infection

A

European bone and joint soc criteria
- clinical features: sinus tract with evidence of communication w joint
- aspiration MCS: >3000 WC/ml and >80% are neutrophils
- positive immunoassay for alpha-defesin in synovial fluid
- >2 out of 5 samples positive for same organism taken at surgery
- histology: >5 neutrophils per field

26
Q

3 surgical Tx for prosthetic joint infection

A

single stage revision
two stage revision
DAIR

27
Q

what is single stage revision

A

remove all foreign material and dead bone
chaneg gloves / drapes
re-implant new prostheses with ABx impregnated cement
+ oral ABx

28
Q

what is two stage revision

A

remove prostheses and put in spacer (to take up space of prostheses)
take samples for micro / histo
period of IV ABx (6 weeks) then stop for 2 weeks
re-bride and sample at second stage
re-implant with ABx impregnated cement
no further ABx if sample is clear, but OPAT used if they are

29
Q

what is DAIR

A

debridement, ABx, implant retention
ABx for 6 weeks

30
Q

when is DAIR used

A

if infection is found within 3 weeks after initial operation

31
Q

epidemiology of surgical sight infections (SSIs

A

0.5 to 10% of all surgeries

32
Q

major pathogens causing SSIs

A

staph aureus
e.coli
pseudomonas aeruginosa

33
Q

pathogenesis of SSIs

A
  1. contamination of wound at operation
  2. inocculum by bacteria
  3. immune suppression due to steroids
34
Q

3 levels of SSIs and definition

A

Superficial incisional - skin and sub cut
deep incisional - fascia / muscle
organ / space infection - any other parts

35
Q

how are SSIs prevented pre op

A

consider age & underlying illness
treat all other infections eg CAP,UTI
pre - op showering
hair removal
nasal decontamination
ABx prophylaxis

36
Q

what illnesses can predispose to SSIs pre op

A

DM
malnutrition
low albumin
radiotherapy / steroids
RA
obesity
smoking

37
Q

how does smoking increase risk of SSIs

A

nicotine delays wound healing
leads to PVD

38
Q

how should RA be controlled prior to surgery to decrease risk of SSI

A

stop DMARDs

39
Q

what is used in pre op showering to reduce risk of SSIs

A

chlorhexidine or normal soap on the day of surgery

40
Q

which hair removal technique increases / decreases risk of SSIs

A

shaving increases
electric clipper decreases

41
Q

what is the most powerful risk factor for SSI post cardiothoracic surg

A

s.aureus in nasal canal

42
Q

how is the risk of SSI decreased intra-op

A

limited number of ppl in theatre
ventilation
sterilisation of instruments
skin prep with chlorhexidine
asepsis surgical technique
normothermia mainatined
oxygenation at 95%

Pathology (87 decks)

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