O&T: A 6 Month Old Child With Bone Pain And Fever

Question 1

History taking of 7-month boy with fever + refuse to crawl

Answer 1

1. Limb movement?
   - Upper e.g. change clothes
   - Lower e.g. change diaper
2. Developmental milestone
3. Vaccination history
4. Past medical history
5. Drug, Allergy
6. Family history

DDx:

• Septic arthritis
• Reactive synovitis after Viral URTI
• Trauma
• Tumour (less likely)

Question 2

***Septic arthritis

Answer 2

• Approximately 0.25% of hospitalisations among children
• More common than Osteomyelitis
• Very quick deterioration course

1. ***Haematogenous seeding of synovium during transient bacteraemia
   - Bacteria spread from Nutrient artery
   —> can still cross Physis since not fused yet
   —> spread into Joint space if Physis is within joint
   - e.g. Otitis media, Sinusitis, UTI
2. Contiguous spread of infection
   - e.g. Penetrating injury with direct inoculation into joint, Adjacent osteomyelitis

Question 3

Physical examination of Septic arthritis

Answer 3

1. Look
   - spontaneous movement of baby
   - swelling
   - deformity
   - bruises
   - normal skin
2. Feel
   - warmth
   - fluctuant
   - crepitus
   - swelling
   - tenderness
3. Move
   - distal to proximal

Question 4

***Investigations of Septic arthritis

Answer 4

Blood:

1. ***CBC + D/C
2. ***CRP, ESR
3. ***Blood culture
4. Clotting profile
5. LRFT

Imaging:

1. X-ray
   - First few days: normal (only Soft tissue swelling)
   - **Bone density: Osteopenia
   - **Shenton’s line: Broken
   - **Soft tissue swelling
   - **Widening of joint space
   - ***Slight subluxation
   - Epiphysis
   - Greater / Lesser trochanter (cannot be seen in baby ∵ still cartilage)
   - Late: Narrowing + Irregularity of joint space
2. USG + Arthrocentesis
   - **WBC >=50,000 (Neutrophil predominant)
   - **Gram stain, Smear, Culture
   - ***High protein + Low glucose
   - Turbid appearance
3. MRI

Question 5

***Management of Septic arthritis

Answer 5

1. Joint Aspiration
   - Hip joint: deep structure (cannot aspirate on your own)
2. Joint ***Decompression + Lavage (Emergency)
   - Arthrotomy / Arthroscopy: open up joint to drain joint fluid
   - rinsing with saline 1-2L
3. Immobilise joint
4. Blood tests to monitor CRP
5. Empirical broad spectrum antibiotic —> More specific
   - **3rd gen Cephalosporin (Ceftriaxone, Cefotaxime)
   —> given after appropriate specimens collected
   —> given until definitive microbiological report is available
   - **3 months (Uncomplicated: 4 weeks until normalisation of CRP, ESR)
   - ***IV —> PO
   —> reduce hospital stay, cost, morbidity, inconvenience to families

Question 6

***Complications of Septic arthritis

Answer 6

1. ***Systemic sepsis
2. ***Premature arthritis (OA)
3. Joint stiffness
4. Effusion compress Circumflex femoral artery —> **Avascular necrosis of proximal femur (can lead to total loss of femoral neck), **Physeal closure, growth disturbance
5. ***Chronic infection
6. ***Pathological fracture

Question 7

***Orthopaedic emergencies

Answer 7

1. Septic arthritis
   - can decompensate very quickly —> Septic shock —> destroy joint capsule
2. Cauda equina syndrome
3. Necrotising fasciitis

Question 8

Intra-articular vs Extra-articular Physis

Answer 8

Intra-articular physis (Physeal growth plate within Joint):
- Shoulder
- Elbow
- Hip
- Ankle
—> Can develop into ***Septic arthritis

Extra-articular:
- Develop into ***Subperiosteal abscess (Osteomyelitis) instead

Question 9

Destruction of articular cartilage

Answer 9

1. ***Proteolytic enzymes released from bacteria + polymorphs
   - loss of Proteoglycans by 5 days
   - loss of Collagen by 9 days
2. ***Impairment of intracapsular vascular supply due to elevated intracapsular pressure
   - Thrombosis of vessel + disruption of blood supply

Question 10

Septic Arthritis vs Transient Synovitis

Answer 10

4 predictors:

1. Fever >38.5
2. Inability to bear weight
3. ESR >40
4. WBC >12,000 or 12

Question 11

Fracture

Answer 11

2 types:

• Stress
• Pathological

Question 12

***Osteomyelitis

Answer 12

Cause:
- Collection of bacteria at 90o turn of Nutrient artery (∵ blood slows down)

Pathogenesis:

1. Inflammation
   - acute inflammatory reaction with vascular congestion —> ***↑ Intra-osseous pressure
2. Suppuration
   - Pus forces through Haversian canals to surface —> ***Subperiosteal abscess
3. Necrosis
   - ↑ Intra-osseous pressure, Thrombosis of vessels, Periosteal stripping —> ***Sequestrum
4. New bone formation
   - forms from deep surface of stripped periosteum —> ***Involucrum

Question 13

Causative agents in Osteomyelitis

Answer 13

Infant:

• ***Staphylococcus aureus
• ***Haemophilus influenzae
• Group B Streptococcus (agalactiae)
• E. coli

1-16:

• ***Staphylococcus aureus
• ***Streptococcus pyogenes
• Haemophilus influenzae

Sickle cell anaemia:
- Salmonella

Adults:

• ***Staphylococcus aureus
• ***E. coli
• Serratia Marcescens
• Pseudomonas aeruginosa

Question 14

Investigations of Osteomyelitis

Answer 14

1. X-ray
   - first 10 days:
   —> ***normal (∵ not enough trabeculae broken down)
   —> only soft tissue swelling

• 10-14 days:
  —> demineralisation at infection site with **new bone formation at the surface
  —> **osteolytic changes present with 50-70% bone loss

2. ***CT
   - better image of bone architecture
3. ***MRI
   - better differentiation between soft tissue vs bone infection
4. Bone scan
5. Gallium scan, WBC scan (not used now)

Question 15

Management of Osteomyelitis

Answer 15

1. Confirm diagnosis
2. Confirm microorganism
3. ***Drain pus + remove all dead bone
4. ***Reconstruct bone
   - Langenskiold operation
5. Reconstruct soft tissues
6. ***Give appropriate systemic antibiotics for adequate duration (minimum 6 weeks)

Question 16

Complications of Osteomyelitis

Answer 16

1. ***Brodie’s abscess
   - subacute osteomyelitis
   - wall formed around infection
2. ***Chronic osteomyelitis
3. ***Metastatic infection
4. Suppurative arthritis
5. ***Physeal disruption
   - if lateral Physis destroyed —> grow slower than medial side —> Valgus deformity