Subacute painful limp with limitation of femoral internal rotation

Specialty: Pediatrics.

• Suspected Perthes disease
• avascular necrosis of the femoral head in children

Why it occurs

• Legg-Calvé-Perthes disease or idiopathic avascular necrosis of the head of the femur (transient ischemia of the femoral ossification nucleus causing collapse, fragmentation and subsequent reossification, typical in male children aged 4 to 10 years)
• Juvenile idiopathic arthritis or JIA (chronic immune-based joint inflammation that insidiously affects large joints)
• Chronic reactive or granulomatous synovitis (secondary to chronic inflammatory or infectious pathologies of low virulence such as mycobacteria)
• Benign or malignant bone tumors of the proximal femur (osteoid osteoma, aneurysmal bone cyst or Ewing sarcoma that weaken the femoral bone structure)

Initial workup

Plain x-ray of the AP pelvis and in the frog position (Lauenstein), essential for the diagnosis and staging of Perthes disease (showing collapse, fragmentation, flattening or subluxation of the femoral head according to the Catterall or Herring stage). Hip ultrasound to rule out chronic joint effusion. Magnetic Resonance (MRI) of the hips (the most sensitive study in early or pre-radiological phases to assess perfusion of the femoral head using contrast with gadolinium). Analysis with blood count and acute phase reactants (CRP and ESR, which are typically normal in Perthes unlike systemic infectious or inflammatory processes).

Standard management

• There is no drug that reverses avascular necrosis; Management is based on joint unloading, physiotherapy and, in severe cases, containment surgery. Ibuprofen — used for pain control and secondary synovitis; dose of 10 mg/kg orally every 8 hours, prescribed temporarily during acute painful flares
• Paracetamol — as a rescue analgesic; dose of 15 mg/kg orally
• Calcium and Vitamin D3 supplements (indicated to optimize systemic bone health during the reossification period if nutritional deficiencies are detected).