A 3-week-old neonate presents with fever, swelling over the left humerus, and reduced limb movement. Blood culture grows Group B Streptococcus. Compared with older children, which feature of neonatal acute haematogenous osteomyelitis explains why multiple bones are frequently involved?

• A Group B Streptococcus has a specific tropism for multiple bones
• B Neonatal bone has a thicker cortex that traps infection in multiple sites
• C Neonatal metaphyseal vessels still penetrate the growth plate, allowing spread between epiphysis, joint and adjacent metaphysis ✓
• D Neonates have absent periosteum, so infection spreads freely along the shaft

Explanation

In the neonate the nutrient vessels of the metaphysis traverse the growth plate to reach the epiphysis, so infection crosses the physis into the epiphysis and joint, producing concurrent septic arthritis and allowing seeding of several bones. Transphyseal vessels regress after about 12 to 18 months, which is why this pattern is rare in older children. The organism is irrelevant to the multiplicity, and the periosteum is present but loosely attached in neonates.

Reference: Tachdjian's Pediatric Orthopaedics, 5th ed.

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Written and medically reviewed by the StethoPrep medical team.