Delbet Classification of Paediatric Hip Fractures

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The Delbet classification, originally described in 1907, separates paediatric proximal femoral fractures into four types based on the fracture line's relationship to the proximal femoral physis and the greater trochanter. The type predicts the risk of avascular necrosis, which remains the most important determinant of long-term outcome.

Understanding why the Delbet types differ in AVN risk requires understanding the paediatric femoral head blood supply:

• The primary supply comes from the lateral epiphyseal arteries (posterosuperior retinacular vessels), which are terminal branches of the medial femoral circumflex artery. These enter posterosuperiorly and are at greatest risk in types I and II.
• The secondary supply comes from the ligamentum teres (foveolar artery), a branch of the obturator artery. This vessel is insignificant in young children and does not compensate when retinacular vessels are torn.
• Metaphyseal vessels contribute from below but cannot cross the physis to reach the epiphysis in children with an open growth plate.
• Type I disrupts the lateral epiphyseal vessels at their entry point through the physis — the proximal fragment is almost entirely devascularised.
• Type II passes through the neck, potentially sparing some retinacular vessels posteriorly if the fracture is undisplaced, but displaced type II fractures tear the same vessels.
• Type III is distal to the main retinacular entry, so more vessels are preserved, but displaced fractures can still damage them.
• Type IV is well distal to the femoral head circulation — AVN is essentially not a concern.

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Management is guided by the Delbet type, the age of the child, the degree of displacement, and the status of the physis. The overarching principles are: urgent capsular decompression, anatomic reduction, stable fixation, and protection of the proximal femoral physis.

Paediatric hip fractures carry one of the highest complication rates of any paediatric fracture. Long-term follow-up to skeletal maturity is mandatory.

• Avascular necrosis of the femoral head is the most common and most devastating complication. It presents clinically with progressive pain, limp, and limited hip movement, typically within the first 1 to 2 years but sometimes later. Radiographic findings include sclerosis, collapse of the femoral head, and secondary osteoarthritis changes. Management of established AVN ranges from containment (bracing, orthoses) in early stages to valgus osteotomy, shelf acetabuloplasty, or ultimately hip arthroplasty in young adulthood.
• Coxa vara occurs from growth arrest of the greater trochanteric apophysis or from malunion of the fracture with a valgus collapse pattern. The neck-shaft angle drops below 110 to 120 degrees, producing a Trendelenburg limp and abductor weakness. A valgus subtrochanteric osteotomy corrects the mechanical alignment and improves abductor function.
• Premature physeal closure of the proximal femoral physis causes progressive limb-length discrepancy and coxa vara. The growth plate contributes approximately 15 percent of total limb length; early closure can produce a significant discrepancy.
• Non-union is seen more often in types I and II and in older children. Treatment is with valgus osteotomy combined with internal fixation and bone grafting.
• Chondrolysis (loss of articular cartilage of the hip) is a rare but serious complication that presents with progressive hip stiffness, pain, and radiographic joint-space narrowing. It is associated with internal fixation penetration into the joint and with prolonged immobilisation.
• Infection after surgical fixation is uncommon but catastrophic in the paediatric hip.
• Pathological fractures in children under 2 years — always screen for underlying pathology, including non-accidental injury, osteogenesis imperfecta, and metabolic bone disease. A transphyseal fracture in a non-ambulating child should raise immediate safeguarding concerns.