Perthes disease (Legg-Calvé-Perthes disease) is a paediatric hip disorder characterised by idiopathic avascular necrosis of the femoral head. It typically affects children aged 4–8 years, with a male predominance (4:1).

Pathophysiology:

The blood supply to the capital femoral epiphysis is disrupted, leading to ischaemia and subsequent necrosis of the femoral head. Over time, revascularisation occurs, but the femoral head may become deformed due to mechanical stress during weight-bearing.

Clinical features:

• Insidious onset of limp or antalgic gait
• Hip, thigh or knee pain
• Reduced range of motion, especially abduction and internal rotation
• Mild muscle wasting around the thigh

Diagnosis:

• X-ray pelvis AP and frog-leg lateral views: Early stages show increased density (sclerosis) of the femoral head; later stages reveal fragmentation, collapse, and eventual reossification.
• MRI can detect early changes before X-ray abnormalities.

Classification: The Herring lateral pillar classification assesses severity based on lateral pillar height on X-ray and predicts prognosis.

Perthes disease - both femoral epiphyses show extensive destruction, the acetabula are deformed © Radiopaedia

Perthes disease - bilateral disease. © Radiopaedia

Treatment principles:

• Aim to maintain femoral head sphericity and containment within the acetabulum during healing.
• Conservative management includes activity modification, analgesia, physiotherapy focusing on maintaining hip range of motion.
• Orthoses (e.g., Scottish Rite brace) or surgical containment procedures (varus osteotomy) may be indicated in moderate to severe cases.
• Prognosis depends on age at onset and extent of femoral head involvement; younger children generally have better outcomes.