Bone and joint infection Flashcards
Is osteomyelitis an infection of the bone or joints?
Osteomyelitis - bones
Septic arthritis - joints
Name some common examples of microbes that cause joint and bone infection.
Staph. aureus (MRSA) Streptococci Enteric bacteria - e.coli/salmonella coagulase -ve staph. cocci Myobacterium TB Lyme, gonorrhoea, brucellosis, fungi, parasites
What factors do you have to consider if bacteria can cause bone and joint infection?
Access, adherence, invasion, multiplication, evasion, resistance, damage, transmission
Describe the host response to infection.
Initially localised to bone cortex
Enlarging abscess, periosteum lifted off bone
sequesterum - avascular necrotic region
Pus escapes through sinus tract
In response to infection, new bone can often form on top of the sequestrum, what is this called?
Involucrum
In response to infection, pus from sequesterum can escape through involucrum (new bone), what is this called?
Cloacae
In chronic osteomyelitis, describe the new bone formed
New brittle bone - darker on x-rays
What can form on prosthetic joints and assist infection?
Biofilm
Clinically, how can you differentiate between osteomyelitis and septic arthritis?
Osteo - fractures/discharging sinuses
Septic arth - damage to articular surfaces
What are the clinical features of osteomyelitis?
Traumaa/penetrating wounds joint replacement abscesses burns pressure ulcers diabetic neuropathy
What investigations would you carry out for infections of joints/bone? (NOT IMAGING)
FBC, CRP
Skin/ulcer swabs
blood cultures (x2)
What imaging techniques could you use for infections of joints/bone? name disadvantages
Radiographs - no early changes
CT - no soft tissue
MRI - no bone
How are joint aspirations carried out and what do they show?
On ward Use local anaesthetic (unless prosthetic) single sample microscopy - WBCs/bacteria/crystals culture, PCR
How are bone biopsies carried out and what do they show?
In theatre
general anaesthetic
multiple samples
culture, PCR, histopathology
What emperical antibiotics would you give to treat infections of the bone/joints initially?
IV flucloxacillin and IV benzylpenicillin (2-6 weeks)
Then 4-6 weeks orally
