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
