4. Infection in Bone and Joints

Question 1

Define osteomyelitis.

Answer 1

Osteomyelitis is an infection of the bone. Can be:

• acute
• chronic
• specific (e.g. TB)
• non-specific (most common)

Question 2

Acute osteomyelitis:

1. T/F: mostly affects children (different ages).
2. T/F: affects more girls.
3. T/F: patients have history of trauma (minor).
4. In adults what other diseases are associated with it?

Answer 2

1. True.
2. False. boys > girls.
3. True.
4. diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell

Question 3

What is the source of infection in acute osteomyelitis?

Answer 3

Children and elderly: haematogenous spread.

Adults: local spread from contiguous (infection spread from one area to adjacent area) site of infection – trauma (open fracture), bone surgery (ORIF), joint replacement
secondary to vascular insufficiency

in infants: infected umbilical cord

in children: boils, tonsilitis, skin abrasions

in adults: UTI, arterial line

Question 4

Which organisms cause acute osteomyelitis?

Answer 4

Infants <1 year: Staph aureus, Group B streptococci, E. coli

Older children: Staph aureus, Strep pyogenes, Haemophilus influenzae (less now due to vaccination)

Adults: Staph aureus (mainly)

• coagulase negative staphylococci (prostheses)
• Propionibacterium spp (prostheses)
• Mycobacterium tuberculosis
• Pseudomonas aeroginosa (esp. secondary to penetrating foot injuries, IVDA

Question 5

Which organisms cause acute osteomyelitis in special cases?

Answer 5

Diabetic foot and Pressure sores - mixed infection including anaerobes

Sickle cell disease – Salmonella spp

Vertebral osteomyelitis – S. aureus, TB

Mycobacterium marinum (fishermen, filleters)

Candida: (debilitating illness, HIV AIDS)
- Long term antibiotic treatment, extensive GI surgery, malignancy

Proteus mirabilis

Brucella (butchers)

Question 6

Acute osteomyelitis is most commonly diagnosed which bones?

Answer 6

Usually can affect any bones but most commonly affects long bones (especially metaphysis) of:

• distal femur
• proximal tibia
• proximal Humerus

Affects joints with intra-articular metaphysis

• hip
• elbow (radial head)

Question 7

Outline pathology of osteomyelitis.

Answer 7

starts at metaphysis – role of trauma?
vascular stasis
(venous congestion + arterial thrombosis)
acute inflammation – increased pressure
suppuration (pus formation)
release of pressure
(medulla, sub-periosteal, into joint)
necrosis of bone (sequestrum)
new bone formation (involucrum)
resolution - or not (chronic osteomyelitis)