Acute Haematogenous Osteomyelitis

Question 1

Epidemiology

Answer 1

1. Disease of peads (commonly 2-6 years old)
2. In adult if low resistant level
   - DM
   - drug abuse
   - malnutrition
   - immunosuppressive therapy

Question 2

Etiology

Answer 2

1. Staph Aureus (70%)
2. GABHS (Chronic skin infection)
3. GBS (newborn babies)
4. H. Influenza (paeds, pre-vaccine)
5. Pseudomonas, proteus (IVDU)

Question 3

Pathology

Answer 3

1. In children
   - Occurs in bone metaphysis
   - hair-pin arrangement of blood vessels (between nutreint artery and sinusoidal veins)
   - prone to stasis
2. In adults
   - 20% of cases
   - usually affecting vertebrae

Question 4

Stage

Answer 4

1. Inflammation
2. Suppuration
   - after 2-3 days, migrates along volkman canal to form subperiosteal abscess
3. Bone necrosis
   - due to increase interosseus pressure, blood flow disruption, thrombosis
   - form sequestra
4. New bone formation
   - fine streaks on x-ray, encasing sequesterum (involucrum)
   - end of second week
5. Resolve/Chronic
   - if infection persist, perforation of involucrum (cloaca), continue with skin sinus

++ adult, children: limited to metaphysis except intraarticular metaphysis
++ infant: small metaphyseal vessels penetrating plate still exist, can spread to epiphysis

Question 5

Extension of pus

Answer 5

1. Along medullary cavity
2. Subperiosteal via Volkmans
3. Joint if metaphysis is intraarticular (hip, shoulder)

Question 6

Route of Infection

Answer 6

1. Children, infant (haematogenous)
   - usually foci of infection not detected
2. Adult (inoculation)
   - open fracture
   - iatrogenic infection
   - unhealing ulcer

Question 7

Complication

Answer 7

1. General
   - sepsis
   - septic shock
2. Local
   - chronic osteomyelitis
   - acute pyogenic arthritis (hip and shoulder) because metaphysis is intracapsular
   - growth plate disturbance
   - pathological fracture

Question 8

CF

Answer 8

1. Newborn
   - tenderness
   - resistance to joint movement
   - FTT
2. Children
   - fever
   - malaise
   - pseudoparalysis
   - refused to be handled or touch
3. Adult
   - mild fever
   - back pain (commonest is thoracolumbar in adult) if haematogenous

Question 9

Investigation

Answer 9

1. Gram staining (60%)
2. Culture (50%)
3. CRP (24 hours)
4. ESR (48 hours)

Question 10

X-Ray

Answer 10

1. 1st week
   - no abnormality in bone
2. 2nd week
   - faint-extracortical outline
   - patchy mottle-appearance
   - regional osteoporosis

Question 11

US

Answer 11

• to detect subperiosteal collection

- however, cannot differentiate pus or blood

Question 12

MRI

Answer 12

• very sensitive (can differentiate om and other soft tissue infection)
• not specific
• only done if diagnosis is doubtful, or involving axial skeleton

Question 13

How to confirm diagnosis?

Answer 13

Fluid/Pus aspirate from metaphyseal subperiosteal abscess, extraosseus tissue or adjacent joint

How?

• using 16-18G trocar needle to aspirate
• gram stain

Question 14

Radionuclides Scanning

Answer 14

• highly sensitive
• not specific

Features: increase activity in perfusion and bone phase

Question 15

Management

Answer 15

1. supportive
   - analgesic
   - hydration
2. splintage
   - comfort
   - prevent joint contracture
   - can also use skin traction, half cylinder?
3. antibiotic
   - iv cloxacillin
   - fusidic acid>benzylpenicillin (high prevalence pf penicillin resistant)
   - iv 2-4 weeks until pt improve, crp, esr, twbc return to normal
   - oral 3-6 weeks
4. surgical drainage
   - often unnecessary. if sx persist >48 hours despite abx therapy
   - if collection of pus seen in us
   - take swab for c/s
   - put suction drain
5. Monitor temperature, vitals chart 4-hourly
6. Aftercare/Discharge
   - restrict weight bearing 6- 8 weeks
   - oral antibiotics for 6 weeks
   - allow partial weight
   bearing with crutches after ifx subsides
   - full weightbearing after 3-4 weeks (children)