bone and joint infections Flashcards
osteomyelitis aetiology
- post trauma or surgery eg. orthopaedic device infection, sporting incidents
- haematogenous
- contiguous with another infection
osteomyelitis pathogenesis
invasive bacteria cause inflammatory reaction
leukocytes release enzymes that lyse the bone
oedema, vascular congestion, and small-vessel thrombosis
impaired flow of both medullary and periosteal blood supply
chronic osteomyelitis
produces areas of devitalized infected bone, sequestra
body forms new bone, involucrum
leads to bone sclerosis and deformity
involucrum
new bone that the body forms
sequestra
areas of devitalized bone
acute osteomyelitis treatment
may be curable with antibiotics alone
chornic osteomyelitis treatment
frequently requires surgical debridement
remove sequestrum and nectrotic tissue
haematogenous OM in adults microbiology
staph aureus
haematogenous OM in infants
staph aureus
strep agalactiae
e coli
haematogenous OM in pre school
staph aureus
strep pyogenes
H influenzae
kingella kingae
also S pneumoniae and salmonella
symptoms of OM
general infection symtoms
fever, pain, erythema, swelling,
brodie abscess
subacute osteomyelitis in children host immunity controls infection leg > arm bones, usually tibia usually S aureus also streptococcus, pseudomonas, haemophilus influenzae, and coag negative staphylococcus increase prevelance of kingella kingae
diagnosis of OM
raised inflammatory markers
- CRP
- white cell count
- others: procalcitonin, IL-6
infections is often very localised, so may not cause a systemic response and these markers may be normal
microbiological
- blood cultures
- joint aspiration and culture
- bone biopsy
imaging - x ray
soft tissue swelling
periosteal reaction - lifting
other imaging for OM
CT
MRI
nuclear scans - not useful, may indicate need for further scans
principles of therapy in antibiotics
high dose antibiotics , usually IV initially
empiric therapy must cover staph aureus eg. flucloxacillin, vancomycin if patient is septic or risks of MRSA, add cephallosporin in kids
at least 6 weeks of therapy in adults
3 weeks sufficient in children
targeted therapy
oral therapy may be effective
principles of therapy in surgery
- acute osteomyelitis may require surgery - drainage of sub periosteal and intra osseous collections
- chronic OM usually requires surgery for debridement, sequestrum, abscess, devitalised tissue
- prosthetic or foreign material needs removal eg. biofilm
septic arthritis pathogenesis
bacteria in the synovium
acute inflammation
no basement membrane, therefore bacteria enter synovial fluid
septic arthritis description
purulent inflammation of joint
synovial hyperplasia
cytokine and proteases release
cartilage destruction and growth inhibition
microbioloty of septic arthritis
MSSA and MRSA
strep species
grem negatives in elderly, catheterised and IDU
N. gonorrhoea
septic arthritis clinically
usually one joint - moost commonly the knee
wrists, ankle hip
sacro-iliac and sterno-clavicular joints in IDU
20% are oligoarticular or polyarticular
joint pain, swelling, warmth, and restricted movement
fever common
diagnosis of septic arthritis
raised inflammatory markers - CRP, white cell count
blood cultures, joint aspiration and culture - culture positive in most, high leucocyte count
septic arthritis treatment
antibiotics and joint drainage
antbiotics choice as per OM
septic arthritis prognosis
inflammaton and destruction of joints may continue even in those with sterile joints despite effective antimicrobial therapy
persistance of bacterial antigens within the joint
50% of s aureus infectons have poor outcome at worse, require arthroplasty
gonococcal arthritis
younger patient group multiple joints may be affected cultures may be negative may be co-existing pastular rash not as joint destructive
