Bone And Joint Infections Flashcards
(36 cards)
Describe the presentation of septic arthritis?
- new onset joint pain (atraumatic)
- hot, red, swollen joint
- reduced ROM
- sepsis
What are the differential diagnoses for a hot, red and swollen joint?
- rheumatoid arthritis
- psoriatic arthritis
- crystal induced arthritis
- trauma
- haemarthrosis
- extra-articular infection: cellulitis/bursitis
Describe the different types of septic arthritis
Haematogenous spread: arising from a distal site (IE/skin infection/RTI/UTI/dental infection) - 80%
Direct inoculation: following surgery/arthroscopy/intra-articular injection/trauma/bite
Contiguous spread: from surrounding structures (osteomyelitis/bursitis/cellulitis/soft-tissue abscess)
What are the diagnostic tests for septic arthritis?
- sepsis/fever >38 degrees (take blood cultures + start antibiotics)
- FBC, CRP, ESR, Us and Es, LFTs
- joint aspirate
What do WCC + synovial fluid results tell you?
High synovial WCC = septic arthritis, crystal-induced arthritis/ inflammatory arthritis
Low synovial WCC = early infections / immunocompromsied / low virulence organisms
What are the possible pathogens that cause septic arthritis?
- S. aureus + enterococci (most common)
- enterobacteriae
- mycobacterium tuberculosis
- neisseria gonorrhoeae
Children:
- streptococcus pneumoniae
- kingella kingae
- haemophilus influenzae type B
What do we consider with a S. aureus positive arthritis?
- source = skin (send swabs for culture), IE
- get blood cultures
- echo (if positive blood cultures)
- IV flucloxacillin/IV vancomycin (MRSA)
What do we consider with a S. viridans arthritis?
- source = mouth, IE
- blood cultures
- echo (if positive blood cultures)
- IV benzylpenicillin/ ceftriaxone/ vancomycin if B-lactam allergy
What do we consider with enterobacteriaceae arthritis?
- source = abdomen/urogenital tract/IE
- urine culture
- imaging of abdomen + pelvis
- IV ceftriaxone/meropenem if ESBL producing/IV gentamicin or ciprofloxacin if B-lactam allergy
Describe the antibiotic management for septic arthritis?
- start empirical antibiotics as per guidelines
- IV
- bactericidal
- spectrum to cover likely pathogens
- consider allergies/toxicities/resistance
- rationalise antibiotics based on culture results and clinical progress
- 4-6 weeks
What antibiotic treatment is given for pseudomonas aeruginosa infection?
IV piperacillin-tazobactam/meropenem/ceftazidime/ ciprofloxacin
What is the effect of periprosthetic joint infections?
- pain
- reduced mobility
- draining sinus
- revision surgery
- prolonged hospital stay
- long antibiotic course
- financial cost
Describe how a biofilm can form in periprosthetic joint infections
- microorganisms can adhere to the surface of the prosthesis and secrete extracellular substances to form a complex glycocalyx matrix
- microorganisms in biofilm communicate through quorum sensing to divide/evade host defence systems/become resistant to microbial therapy
Describe the presentation of acute PJI
- acute = immature biofilm
- red, hot, painful joint
- fever/sepsis
- prolonged leaking wound post-operatively
Describe the presentation of chronic PJI
- chronic = mature biofilm
- pain
- stiffness
- loosening of prosthesis on X-ray
- mildly raised inflammatory markers
- difficult to distinguish from aseptic loosening
Describe the pathogenesis of PJI
Early: within 4 weeks of implantation
- virulent pathogens (eg. S. Aureus/ strep/ aerobic gram-negative rods - E. coli, enterobacter spp., klebsiella spp., pseudomonas aeruginosa)
- acute presentation
Delayed 3 months- 3 years after implantation
- low virulence organisms (eg. Coagulase negative staphylococci/cutibacterium acnes)
How would you diagnose a PJI infection?
Joint aspirate:
- WCC/ % PMN
- microscopy
Blood cultures
Biomarkers (in chronic)
Send multiple samples from separate sites (pus, fluid, synovium, membrane, bone)
Intra-operative samples:
- microbio = at least 2 intraoperative samples with the same microorganisms (unless virulent, then 1 is enough)
- histopatho = at least 5 neutrophils per high power field
Describe how you can disrupt a prosthetic joint biofilm
Beadmill processing: shaking with glass beads to disrupt the biofilm and dissociate bacteria from biofilm
Sonification of explanted prosthesis: low intensity ultrasound to disintegrate biofilm (then culturing the sonicated fluid)
Describe how laboratory antibiotic sensitivity testing occurs
- disc diffusion agar plate with antibiotic impregnated discs
- zone of inhibition forms around the discs to indicate antibiotic activity
- zone measured and colony growth compared to note which antibiotic is effective
Describe the surgical strategies that can be implemented to treat PJI
- debridement, antibiotics and implantation retention (DAIR) - radical debridement/ thorough joint washout/ exchange of polyethylene liners
- complete removal of prosthesis: one/two stage exchange
- amputation
Describe antimicrobial management of PJI
- delay until theatre samples are taken unless patient is septic/clinically unstable
- empirical gram positive and gram negative cover (vancomycin/gentamicin)
- rationalise to pathogen-directed IV/highly bioavailable antimicrobials (after causative organism found)
- 6 weeks following removal / 3-6 months following DAIR
- antibiotic suppressive therapy (long term)
Describe the Cierny-Mader classification
Anatomical type:
* stage 1 = medullary
* stage 2 = superficial
* stage 3 = localised
* stage 4 = diffuse
Host-physiology: A (no systemic/local compromising factors), B (systemic and/or local compromising factors), C (severely compromised/not surgical candidate)
What are the limitations of the Cierny-Mader classification of osteomyelitis?
- does not take duration of symptoms into account
- placing patients in category C is subjective
Describe the Waldvogel classification of osteomyelitis
Duration of symptoms: acute (days/weeks), chronic (months/years/persistent infection/low grade infection/sequestrum/fistulous)
Pathogenesis: haematogenous, contiguous
Presence or absence of vascular insufficiency (diabetic foot infection, poor glycaemic control/ischaemic bone and soft tissue/peripheral neuropathy)