A 3-year-old child has acute haematogenous osteomyelitis of the proximal femur for 10 days without treatment. X-ray shows periosteal elevation and a lytic area in the metaphysis. The hip is held in flexion and external rotation. Which complication is MOST immediately threatening?

• A Pathological fracture through the lytic metaphyseal lesion
• B Growth arrest and leg-length discrepancy from physeal involvement
• C Brodie's abscess formation requiring surgical drainage
• D Secondary septic arthritis of the hip joint causing avascular necrosis ✓

Explanation

In children under 18 months (and up to 2–3 years for the proximal femur specifically), the metaphysis is intracapsular. Subperiosteal pus can decompress into the hip joint, causing secondary septic arthritis. Septic arthritis of the hip leads to rapid destruction of the femoral head cartilage and AVN due to tamponade of the retinacular vessels by intra-articular pressure — the most immediately devastating complication. Growth arrest is a later complication; Brodie's abscess represents chronic subacute osteomyelitis (Garre pattern); pathological fracture is possible but less acute than joint destruction.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.