A 5-year-old boy presents with 48 hours of fever and severe pain over the distal tibial metaphysis. Plain radiograph of the leg is reported as completely normal. What is the most likely explanation for the normal radiograph?

• A The child most likely has transient synovitis rather than a bone infection
• B The tibia cannot be affected by haematogenous osteomyelitis at this age
• C Osteomyelitis produces only soft tissue changes that are never visible on plain film
• D Radiographic changes of acute osteomyelitis take 10 to 14 days to become visible ✓

Explanation

Plain films require 30 to 50 percent demineralisation or cortical loss before lysis becomes visible, so bony change lags 10 to 14 days behind symptom onset. The earliest detectable signs are soft tissue swelling and loss of deep fascial planes within the first few days. D normal early radiograph therefore does not exclude osteomyelitis, and MRI should be obtained when clinical suspicion persists.

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

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