A 2-year-old child with septic arthritis of the hip is taken for emergency surgical drainage. During the procedure, the surgeon must understand that in this age group, the femoral head blood supply is most likely to be compromised because:

• A Epiphyseal arteries cross the physis and can be torn during traction
• B A transphyseal anastomosis supplies the epiphysis and is the only blood supply at this age
• C The ligamentum teres artery is the dominant blood supply and thromboses with joint sepsis
• D The medial circumflex femoral artery (MCFA) branches run in the retinacular folds and can be compressed by intra-articular pus ✓

Explanation

In neonates and young infants (<18 months), the femoral head is supplied primarily by metaphyseal vessels that cross the physis AND by retinacular vessels (branches of MCFA). Elevated intra-articular pressure in septic arthritis tamponades the retinacular vessels running through the joint capsule, causing avascular necrosis. In children >4 years, transphyseal vessels have disappeared and the MCFA retinacular branches become the dominant supply. The ligamentum teres artery supplies only 20–30% of the femoral head and is insufficient as a sole supply.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.