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CNSLF Micro - Bone & Joint Infections (i) (Prosthetic joint infections…
CNSLF Micro - Bone & Joint Infections (i)
Acute vs chronic
pathogenesis
organisms
clinical presentation
management
Native bone/joint vs prosthetic material
pathogenesis
organisms
clinical presentation
management
TB of bones + joints
increased incidence recently due to HIV
spine (esp thoracic - T10-11 - Pott's disease), hip, knee (weight-bearing)
clinical features
slow onset chronic mono arthritis
usually no systemic symptoms
swelling may be marked, but signs of acute inflamm absent or mild
spinal TB
collapse of intervertebral disc
psoas abscess may spread to groin
paraplegia secondary to pressure on spinal cord
dx
aspirate
ZN stain
culture
synovial fluid culture +ve in 80-90%
imaging: see joint space narrowing + bone erosions
management
anti-TB drugs usually eradicate, but may need surgery
tx required for up to 12 months
Lyme disease
chronic monoarthritis with large joint effusions 6 months after initial untxed infection
dx confirmed by serology
tx = ceftriaxone
Brucella
B melitensis + B abortus
sacroiliac joints + spine affected
dx by serology
salmonella species
may infect bones via bloodstream in sickle cell disease
Bacteroides actinomyces
trauma
Reactive arthritis
sterile joint inflamm that may be related to infection @ distant site
immunological antigenic cross reaction between synovial membrane + cell wall
consider if recent GIT or GUT infection with acute sterile arthritis
yersinia, campylobacter, salmonella, chlamydia (Rieter's), post-strep
HLA B27 histocompatibility @ increased risk
Viral arthritis
causative pathogens
parvovirus
HBV
HCV
rubella
chikungunya
zika
depends on travel + country or residence
clinical presentation
acute poly arthritis of small + large joints
fever
rash
dx = serology
management = supportive, mostly self-limiting
Prosthetic joint infections
0.5-2% of hip + knee replacements
early = <3 months of joint implant - results from peri/post op wound infection - usually S aureus
delayed = 3-24 months - coag -ve staph, s aureus, strep occasionally, GNB, candida
late = >24 months after implant - note a/w procedure, just bacteraemia that seeded in prosthesis (haematogenous) - S aureus, gram -ves, anaerobes
clinical features
early: pain, erythema, drainage @ wound site
delayed: gradually progressive joint pain
late: haematogenous symptoms e.g. fever
dx
inflamm markers - e.g. CRP useful
radiology: may see loosening which may be mechanical or septic (non-specific)
joint fluid aspiration or tissue
while international guidelines + some consensus exists, management is individual patient-focused
some cases may respond to aspiration/drainage, debridement + antibiotics for 12+ wks
removal of joint often required - 2 stage procedure
removal of prosthesis, insert cement spacer + IV antibiotics for 6 wks
then reinsert new prosthesis
usually combo of antibiotics based on likely pathogens (NB cover cover coag -ve staph with vanc
prevention
avoid introducing bacteria into joints
pre-op MRSA screening + decolonisation
ultra clean theatres for orthopaedic surgery
pre-op skin antisepsis
appropriate preop antibiotic prophylaxis (without this then 50% would become infected)
biofilm protects bacteria + makes eradication difficult