Osteomyelitis

Question 1

What is osteomyelitis?

Answer 1

Osteomyelitis is an infection in the bone and bone marrow.

Question 2

Give examples of organisms commonly causing osteomyelitis

Answer 2

Common organisms implicated in acute osteomyelitis are Staphylococcus aureus, streptococci, Enterobacteriaceae and anaerobic bacteria.

Question 3

Which bones are commonly affected in osteomyelitis?

Question 4

What are the risk factors for osteomyelitis?

Answer 4

• Previous osteomyelitis
• Penetrating injury
• Intravenous drug misuse, diabetes
• HIV infection
• Recent surgery
• Distant or local infection
• Sickle cell disease
• Rheumatoid arthritis
• Chronic kidney disease,
• Immunocompromising conditions

Question 5

What are the signs of osteomyelitis?

Answer 5

• Local inflammation, tenderness, erythema and swelling
• Limited range of movement

Question 6

What are the symptoms of osteomyelitis?

Answer 6

• Limp or reluctance to weight bear
• Non-specific pain at the site of infection
• Malaise and fatigue
• Fever
• Local back pain with systemic symptoms
• Paravertebral muscle tenderness and spasm

Question 7

What do the symptoms of local back pain with systemic symptoms and paravertebral muscle tenderness and spasm indicate?

Answer 7

May indicate native vertebral osteomyelitis.

Question 8

What investigations should be ordered for osteomyelitis?

Answer 8

• FBC
• ESR
• CRP
• Blood culture
• X-ray
• MRI
• Bone samples and biopsy

Question 9

Why investigate FBC?

Answer 9

Useful in acute osteomyelitis and early fracture-related infection, when it is usually raised; however white cell count has a low specificity for osteomyelitis.

Usually normal in chronic disease.

Question 10

Why investigate ESR?

Answer 10

Usually raised but may be normal; non-specific, also raised in other inflammatory conditions and in malignancy. Can be used to monitor treatment; if persistently raised after treatment, should trigger further assessment.

Question 11

Why investigate CRP?

Answer 11

Usually raised. May be more helpful than ESR in monitoring response to treatment because it normalises more rapidly. Non-specific.

Question 12

Why investigate using blood culture?

Answer 12

Aim to take blood for culture before starting antibiotics to guide ongoing care.

May be positive, indicating the infecting organism and microbial sensitivities.

Question 13

Why investigate using x-ray of the affected area?

Answer 13

Always request x-rays to look for evidence of peripheral osteomyelitis, as well as other pathologies such as fractures or bone tumours

In acute disease osteopenia appears 6-7 days after infection onset, and evidence of bone destruction, cortical breaches, and periosteal reaction follow quickly.

Question 14

What can be seen on an x-ray of vertebral osteomyelitis?

Answer 14

Initially shows localised rarefication (‘thinning’) of a single vertebral body, and then later, anterior bone destruction.

Question 15

Why investigate using bone samples and biopsy?

Answer 15

Bone marrow aspiration or bone biopsy with histology and culture may be necessary.

May be positive, indicating the infecting organism and microbial sensitivities.

Question 16

Why investigate using MRI?

Answer 16

MRI is usually the most definitive and helpful imaging modality. May show signs of infection in the medullary canal or surrounding soft tissues.

Question 17

Briefly describe the treatment for osteomyelitis

Answer 17

In acute osteomyelitis:

• Follow local protocols for empirical antibiotic choice
  
  • Once the diagnosis has been confirmed and results of cultures and sensitivities are known, modify the antibiotic regimen accordingly
• Offer analgesia
• Immobilise the limb for comfort if required
• Monitor and manage comorbidities during the hospital stay
• Seek specialist advice on the need for surgical management (e.g., debridement or drainage of abscesses), in addition to antibiotic therapy

Question 18

What is the first-line treatment in osteomyelitis?

Answer 18

Flucloxacillin IV 2g for 6 weeks for an acute infection.

Question 19

If the patient has an allergy to penicillin, what antibiotic can be used?

Answer 19

Vancomycin.

Question 20

How long are antibiotics given for in osteomyelitis?

Answer 20

Generally, give antibiotics for 6 weeks in total.

Give a short course of intravenous therapy initially, and then switch to oral antibiotics when clinically indicated.

Question 21

When are surgical procedures used in osteomyelitis?

Answer 21

If any diagnosis is delayed, dead bone or abscesses are present, response to antibiotics is slow, or a septic arthritis is associated with the osteomyelitis, additional treatment, such as drainage or surgery, will often be required.

Question 22

What are the complications of osteomyelitis?

Answer 22

• Amputation
• Growth disturbance in children and adolescents
• Recurrent infection
• Fracture

Question 23

What differentials should be considered in osteomyelitis?

Answer 23

1. Septic arthritis
2. Juvenille idiopathic arthritis
3. Transient synovitis

Question 24

How does osteomyelitis and septic arthritis differ?

Answer 24

Differentiating signs and symptoms:

• More prevalent in children
• Inflammatory signs specifically around the joint
• Pain is worse on movement of the joint in septic arthritis
• Osteomyelitis can co-exist with septic arthritis

Differentiating investigations:

• Analysis of joint aspirate will demonstrate raised white cell count and infecting organisms
• X-ray may show joint effusion

Question 25

How does osteomyelitis and juvenille idiopathic arthritis differ?

Answer 25

Differentiating signs and symptoms:

• Common in children
• Chronic illness > six weeks
• Associated with a rash and morning stiffness

Differentiating investigations:

• Antinuclear antibodies (ANA) are detected in about one third of children
• Analysis of joint aspirate will demonstrate sterile effusion

Question 26

How does osteomyelitis and transient synovitis differ?

Answer 26

Differentiating signs and symptoms:

• A self-limiting inflammatory disorder of the hip that commonly affects young children and is more common in boys
• Presents acutely with mild to moderate hip pain and limp and often follows a viral illness

Differentiating investigations:

• Inflammatory markers may be normal, or slightly raised, whereas in acute osteomyelitis they would be more markedly elevated
• X-ray is typically normal