Bone and Joint Infection

Question 1

What are the common causative pathogens for septic arthritis?

Answer 1

• MSSA/MRSA
• S. pyrogenes
• Group A Strep
• Pneumococcus (commoner in children)
• H. influenzae
• Kingella
• N. meningitides
• N. gonorrhoea
• E. coli
• P. aeruginosa
• Salmonella species

Question 2

What are the risk factors for prosthetic joint infections?

Answer 2

• Primary arthroplasty (RA, DM, poor nutritional status, obesity, concurrent UTI, steroids and malignancy)
• Revision arthroplasty (prior joint surgery, prolonged operating room time, pre-op infection)

Question 3

What are the common causative pathogens of prosthetic joint infections?

Answer 3

• S. aureus
• Coagulase-negative Staphylococci
• Streptococci
• Gram-neg bacilli
• Anaerobic organisms
• Enterococcus

Question 4

What is the pathogenesis of prosthetic joint infections?

Answer 4

• Local spread (direct contact) is most common and usually manifests immediately post-op
• Haematogenous spread presents later
• Other factors include the avascular surface allowing survival of bacteria and cement inhibiting phagocytosis and lymphocyte/complement function

Question 5

What is osteomyelitis?

Answer 5

• Progressive infection of bone characterised by death of bone and the formation of sequestra

Question 6

What are the clinical features of vertebral discitis?

Answer 6

• Infection of disc space and adjacent vertebral end plates
• Can be very destructive with deformity, spinal instability risking cord compression, paraplegia and disability

Question 7

• How are septic arthritis, prosthetic joint infections and osteomyelitis treated?

Answer 7

• Septic = 2/3 weeks IV then 3 weeks of oral antibiotics
• Prosthetic = antibiotics that can penetrate bone (cephalosporins, tazocin, carbapenems etc.)
• Osteomyelitis = surgery to debulk, stabilise fractures and antibiotics 4-6 weeks IV