Bone and Joint Infection

Question 1

What are the three routes of acquiring osteomyelitis infection?

Answer 1

1. Post-trauma, e.g. surgery
2. Haematogenous (long bones in children, vertebrae in adults)
3. Contiguous with another infection (e.g. diabetic foot infection)

Question 2

What are the steps in the pathogenesis of osteomyelitis

Answer 2

1. Invasive bacteria cause inflammation
2. Leukocytes secrete enzymes that lyse bone
3. Causes oedema, vascular congestion and small vessel thrombosis
4. Areas of devitalised bone form = sequestrum
5. Body forms new bone = involucrum
6. Results in bone sclerosis and deformity

Question 3

Differences in treatment of acute vs chronic osteomyelitis?

Answer 3

Both require high dose antibiotics, usually intravenously

• Flucloxacillin - empirical therpay to cover S.aureus

Acute osteomyelitis may require drainage of sub-periosteal and intra-osseuous abscesses

Chronic osteomyelitis will require debridement of sequestrum, abscesses and necrotic tissue.

Question 4

What is the most common cause of osteomyelitis?

Answer 4

Staphylococcus aureus

Question 5

What are three common causes of osteomyelitis from haematogenous spread or contiguous infection?

Answer 5

• S. aureus
• Beta-haemolytic strep
• Gram negative organisms

Question 6

What are the common causes of haematogenous spread to osteomyelitis in infants?

Answer 6

Staph aureus

Strep agalactiae

E. coli

Question 7

What is a brodie abscess?

What is the most common causative organism?

Answer 7

Subacute osteomyelitis which has been contained by the host immune system

Results in an abscess in the bone, characterised by a circular ‘hole’ shown on CT or X-ray.

Caused by S aureus

Question 8

How is osteomyelitis diagnosed?

Answer 8

• BLood cultures
• Joint aspiration + culture
• Bone biopsy