Mi - Wound, Bone & Joint Infections Flashcards
incidence of septic arthritis
2 to 10 per 100,000
in whom is septic arthritis more common
RA patients (28-38 per 100,000)
mortality and morbidity of septic arthritis
mortality = 7-15%
morbidity = 50%
Rfs of septic arthritis
RA
osteoarthritis
joint prosthesis
IVDU
DM, chronic renal disease, chronic liver disease
steroids / immunosuppression
trauma - intra-articular or penetrating injury
pathophysiology of septic arthritis
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
bacterial factors of septic arthritis pathogenesis
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
host factors for septic arthritis pathogenesis
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
common causative organisms of septic arthritis
& less common causes
STAPH AUREUS no1
strep - pyogenes, pneumoniae, agalactiae
some gram negatives
less common
- lyme disease
- brucellosis
- mycobacteria
- fungi
clinical features of septic arthritis
1-2 wk history of red /swollen joint, restricted movement
monoarticular (90%) - usually knee (50%)
Ix for septic arthritis
blood culture if pyrexial
synovial fluid aspiration for MCS - can be USS guided
ESR, CRP
CT / MRI
synovial count cut off for septic arthritis diagnosis
> 50,000 WBC/mL
Mx of septic arthritis
ABx - IV cephlasporin / fluclox
+/- vancomycin if MRSA
IV for 2 weeks then oral for up to 4 weeks
arthroscopic washout
cause of vertebral osteomyelitis
acute haematogenous
exogenous - after disc surgery / implant assoicated
causative organisms of vertebral osteomyelitis
s.aureus #1
coagulase neg staphylcoccus
gram neg rods
streptococci
most common site of infection of vertebral osteomyelitis
lumbar
cervical
sx of vertebral osteomyelitis
back pain
fever
neuro impairment if cord compression
Dx of vertebral osteomyelitis
MRI - 90% sensitive
blood cultures
CT / open biopsy
Tx of vertebral osteomyelitis
6 weeks of ABx
- longer if undrained collections / implant associated
surgery if spinal cord compression
Sx of chronic osteomyelitis
pain
brodies abscess
sinus tract
Dx of chronic osteomyelitis
MRI
bone biopsy - culture and histology
Tx of chronic osteomyelitis
masquelet technique
oral ABx (up to 6 weeks)
what is masquelet technique
- 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
Sx of prosthetic joint infection
pain around joint
patient complains joint was never right
early failure
discharging sinus tract
causative organisms of prosthetic joint infection
gram positive cocci
staph aureus
less common is gram neg
Dx of prosthetic joint infection
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
3 surgical Tx for prosthetic joint infection
single stage revision
two stage revision
DAIR
what is single stage revision
remove all foreign material and dead bone
chaneg gloves / drapes
re-implant new prostheses with ABx impregnated cement
+ oral ABx
what is two stage revision
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
what is DAIR
debridement, ABx, implant retention
ABx for 6 weeks
when is DAIR used
if infection is found within 3 weeks after initial operation
epidemiology of surgical sight infections (SSIs
0.5 to 10% of all surgeries
major pathogens causing SSIs
staph aureus
e.coli
pseudomonas aeruginosa
pathogenesis of SSIs
- contamination of wound at operation
- inocculum by bacteria
- immune suppression due to steroids
3 levels of SSIs and definition
Superficial incisional - skin and sub cut
deep incisional - fascia / muscle
organ / space infection - any other parts
how are SSIs prevented pre op
consider age & underlying illness
treat all other infections eg CAP,UTI
pre - op showering
hair removal
nasal decontamination
ABx prophylaxis
what illnesses can predispose to SSIs pre op
DM
malnutrition
low albumin
radiotherapy / steroids
RA
obesity
smoking
how does smoking increase risk of SSIs
nicotine delays wound healing
leads to PVD
how should RA be controlled prior to surgery to decrease risk of SSI
stop DMARDs
what is used in pre op showering to reduce risk of SSIs
chlorhexidine or normal soap on the day of surgery
which hair removal technique increases / decreases risk of SSIs
shaving increases
electric clipper decreases
what is the most powerful risk factor for SSI post cardiothoracic surg
s.aureus in nasal canal
how is the risk of SSI decreased intra-op
limited number of ppl in theatre
ventilation
sterilisation of instruments
skin prep with chlorhexidine
asepsis surgical technique
normothermia mainatined
oxygenation at 95%
