Osteomyelitis

Question 1

What is osteomyelitis?

Answer 1

Progressive infection of the bone [or bone marrow] and surrounding soft tissue often caused by pyogenic bacteria

Question 2

What are the different types of bone infection?

Answer 2

• Acute
• Chronic
• Specific (eg TB)
• Or non-specific (most common)

Question 3

Who does acute osteomyelitis commonly affect? And RF?

Answer 3

• Mostly children (different ages)
• Boys > girls
• History of trauma (minor)
• Other disease
  
  • Diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell

Question 4

How does acute osteomyelitis spread?

Answer 4

• haematogenous: children and elderly
• local: from contiguous site of infection
• trauma (open fracture)
• bone surgery (ORIF)
• joint replacement
• secondary to vascular insufficiency

Question 5

What are some of the sources of infection in acute osteomyelitis?

Answer 5

• In infants: infected umbilical cord
• In children: boils, tonsilitis, skin abrasions
• In adults: UTI, arterial line

Question 6

What are the most common infection organisms in acute osteomyelitis?

Answer 6

Staph aureus

Question 7

Which long bones are affected by acute osteomyelitis?

Answer 7

Effects long bones at the metaphysis:

• Distal femur
• Proximal tibia
• Proximal Humerus

Question 8

Which joints are affected by acute osteomyelitis?

Answer 8

Effects joints with intra-articular metaphysis:

• Hip
• Elbow

Question 9

What are 8 steps of pathogenesis of acute osteomyelitis?

Answer 9

1. Starts at metaphysis
2. Vascular stasis (venous congestion and arterial thrombosis)
3. Acute inflammation - increased pressure
4. Suppuration
5. Release of pressure
6. Necrosis of bone (sequestrum)
7. New bone formation (involucrum)
8. Resolution (or not)

Question 10

What are clinical features of acute osteomyelitis in infant?

Answer 10

• Aysmptomatic or very ill
• Failure to thrive
• Drowsy/irritable
• Metaphyseal tenderness and swelling

Question 11

What are clinical features of acute osteomyelitis in children?

Answer 11

• Severe pain
• Reluctancy to move; not weight bearing
• May have swinging pyrexia and tachycardia
• Malaise

Question 12

What are clinical features of acute osteomyelitis in adults?

Answer 12

• Primary OM seen commonly in thoracolumbar spine
• Backache
• History of UTI
• Elderly, DM, immunocompromised
• Secondary OM is far more common: often after open fracture or surgery

Question 13

What do we do to diagnose acute osteomyelitis?

Answer 13

• History and examination
• FBC and diff WBC
• ESR, CRP
• Blood cultures x3 (at peak of temp. 60% will be positive)
• U&Es

Question 14

DDx for acute osteomyelitis?

Answer 14

• Acute septic arthritis
• Acute inflammatory arthritis
• Trauma (fracture, dislocation, etc.)
• Transient synovitis (“irritable hip”)
• Soft tissue infection
  • Cellulitis
  • Necrosing fasciitis
  • Erysipelas

Question 15

What investigations do we run for acute osteomyelitis?

Answer 15

• X-ray (normal in the first 10-14 days)
• Ultrasound
• Aspiration
• Isotope Bone Scan (Tc-99, Gallium-67)
• Labelled white cell scan (Indium-111)
• MRI

Question 16

What can be seen on radiographs as acute osteomyelitis progresses?

Answer 16

• Early radiograph: minimal changes
• 10-20 days early periosteal changes
• medullary changes - lytic areas
• late osteonecrosis - sequestrum
• late periosteal new bone - involucrum

Question 17

What is the Tx for acute osteomyelitis?

Answer 17

supportive treatment for pain and dehydration

• general care and analgesia

rest and splintage

antibiotics

• route (IV/oral switch – 7-10 days?)
• duration (4-6 wks – depends on response, ESR)
• choice - empirical (Fluclox + BenzylPen) while waiting

Question 18

Why will antibiotics sometimes fail as treatment for acute osteomyelitis?

Answer 18

• Drug resistance
• Bacterial persistance
• Poor host defences
• Poor drug absorption
• MRSA etc….

Question 19

When is surgery indicated for acute osteomyelitis?

Answer 19

Once there is dead bone or biofilm established antibs alone cannot cure and thorough surgical debridment is required.

• Aspiration of pus for diagnosis & culture
• Abscess drainage
• Timing, drainage, lavage

Question 20

Complications of acute osteomyelitis?

Answer 20

• Septicaemia, death
• Metastatic infection
• Pathological fracture
• Septic arthritis

Question 21

What causes chronic osteomyelitis?

Answer 21

• May follow on from acute osteomyelitis
• May start de novo: following an operation, following open fracture, immunosuppresed, DM, elderly
• Repeated breakdown of healed wounds

Question 22

What is the causative organism for chronic osteomyelitis?

Answer 22

Mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus

Question 23

What are the 4 steps for pathogenesis of chronic osteomyelitis?

Answer 23

1. Cavities
2. Dead bone (retained sequestra)
3. Involucrum
4. Histological picture is one of chronic inflammation

Question 24

What are the complications of chronic osteomyelitis?

Answer 24

• Chronically discharging sinus + flare-ups
• Ongoing infection
• Pathological fracture

Question 25

What are some of the Tx options for chronic osteomyelitis?

Answer 25

* long-term antibiotics * Eradicate bone infection surgically * Treat soft tissue problems