9.8 Bone & Joint Infections

Question 1

What is the most common causative organism of osteomyelitis in adults?

Answer 1

Staphylococcus aureus

Question 2

What are some ways/circumstances in which bacteria can reach bone and cause osteomyelitis?

Answer 2

• Bloodstream spread
• Trauma (e.g. open fracture)
• Surgery

Question 3

What is the effect of osteomyelitis on the balance of bone remodelling? Why?

Answer 3

• Phagocytic immune cells release proteolytic enzymes in an attempt to kill the pathogen
• In the process, can increase osteolysis in surrounding region

Question 4

Describe 4 complications of osteomyelitis

Answer 4

1. Osteonecrosis (sequestrum formation)
2. Septic arthritis (if spreads to joint)
3. Impaired growth (if epiphyseal lines have not fused)
4. Sepsis

Question 5

Describe treatment of osteomyelitis

Answer 5

• Surgery (pus drainage, removal of necrotic tissue, amputation as a last resort)
• Intravenous antibiotics; targeted based on organism

Question 6

Describe diagnosis of osteomyelitis

Answer 6

• Palpate for tenderness, swelling and warmth
• Bloods (?WBC inc, blood culture, ?CRP/ESR raised)
• Imaging (marrow oedema)

Question 7

How does osteomyelitis lead to bone necrosis?

Answer 7

• Inflammatory exudate leaks into periosteum
• Compresses blood supply
• Leads to ischaemia and necrosis

Question 8

Histological signs of osteomyelitis (acute/chronic)

Answer 8

Acute: neutrophil infiltration

Chronic: necrotic bone (no osteocytes)

Question 9

Other than staph aureus, list two other causative organisms of osteomyelitis.

Answer 9

• Salmonella
• Mycobacterium tuberculosis