Osteomyelitis

Question 1

Define the term osteomyelitis

Answer 1

Inflammation of bone, usually caused by bacteria but occasionally by mycobacteria or fungi

Question 2

How do pathogens reach bones?

Answer 2

• Haematogenous
• Traumatic spread
• Diabetes
• Contiguous spread (cutaneous, dental, sinus, aural)

Question 3

What are the main sources of bacteria in haematogenous osteomyelitis?

Answer 3

• Staphylococcus Aureus (primary unknown source)

cutaneous, dental, aural, sinus

Question 4

Discuss the pathogenesis of haematogenous osteomyelitis in children and in adults

Answer 4

1. Begins with subclinical haematogenous spread of staph aureus
2. An acute inflammatory focus develops in a bone
   - children = metaphysis of long bones
   - adults = diaphysis of small bones, vertebrae, pelvis
3. Bone necrosis
   - inflammation and oedema of the bone = compression of adjacent vessels??
   - the infection causes death of bone leading to sequestrum (separation of death bone from living bone)
4. Reactive bone growth
   - In children the inflammatory exudate may extend to the bone surface = oedema and abscess formation which leads to periosteal elevation
   - the lifting of the periosteum also stimulates osteoblasts leading to the formation of an involucrum (bone surrounding infection)
5. Sinus formation
   - In children the pus and necrotic tissue can drain towards the skin creating a superficial drainage site = cloaca

In adults
it is rare for stage 4 and 5 to occur

Question 5

Discuss the typical clinical picture of acute haematogenous osteomyelitis in children and adults

Answer 5

Children

• sudden onset high fever with chills and malaise
• progressively increasing local pain
• oedema and warmth over affected bone
• local mm spasm

Adults

• insidious onset of fever with vague ssx malaise, anorexia
• recent Hx of infection (UTI) or instrumentation

Vertebral Osteomyelitis:
- back pain (intermittent, worse with ROM, =/- radicular)
- spinal tenderness/rigidity 
- hip contracture (psoas irritation)
Sacroiliac Osteomyelitis:
- severe ssx 
- limp
- local pain/tenderness 
- radiation of pain into abdo/buttocks