A 7-year-old boy presents with a 3-day history of fever, right knee pain, and refusal to weight-bear. MRI demonstrates subperiosteal abscess with periosteal elevation. Blood culture grows Staphylococcus aureus sensitive to flucloxacillin. According to Nade's classification and the Cierny-Mader staging system (paediatric context), which histological type of osteomyelitis best describes this presentation?

• A Cierny-Mader Type II (superficial) — cortical osteomyelitis from contiguous focus
• B Cierny-Mader Type IV (diffuse) — chronic throughout bone requiring bone resection
• C Cierny-Mader Type I (medullary) — haematogenous osteomyelitis confined to the medullary canal ✓
• D Cierny-Mader Type III (localised) — full-thickness cortical involvement with focal sequestrum

Explanation

The Cierny-Mader classification categorises osteomyelitis by anatomical type and host physiological status. Type I (medullary) represents haematogenous osteomyelitis where infection is confined to the medullary canal — the typical acute haematogenous osteomyelitis of childhood. The infection begins in the metaphyseal sinusoids, forms a subperiosteal abscess through perforation of thin metaphyseal cortex, and produces periosteal elevation. MRI with subperiosteal abscess but no sequestrum in a febrile child with haematogenous source is classic Type I. Treatment is systemic antibiotics with surgical drainage if abscess is present.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.