Late-onset Legg-Calvé-Perthes Disease Treated with Varus Derotation Femoral Osteotomy: A Case Report.

Introduction: Legg-Calvé-Perthes disease (LCPD) is categorized as idiopathic avascular necrosis of the femoral head, most common in children between the ages of 5 and 7. Prognosis is strongly influenced by age and lateral pillar classification, with children older than 8 years and those with Herring Group C disease typically experiencing poor outcomes. Delayed diagnosis represents a significant barrier to care, often limiting treatment options and worsening prognosis. This case highlights such a scenario while demonstrating that favorable functional and radiographic results remain achievable through meticulous surgical containment in late-presenting, severe disease. Case Report: An 11-year-old boy with no history of trauma or systemic illness presented with an 8-month history of progressive right hip pain and a severe antalgic gait. On physical examination, he was observed to have severely restricted hip abduction and rotation. Radiographs demonstrated fragmentation, loss of sphericity, and reduced lateral pillar height of the right femoral head, consistent with Herring Group C disease. Magnetic resonance imaging confirmed avascular necrosis. Pre-operative planning targeted correction of a neck-shaft angle of 140-120° with 20° derotation. A varus derotation osteotomy of the proximal femur was performed through a lateral approach, with fixation using a plate and screws. Postoperatively, the patient was immobilized and received routine wound care. At follow-up, the patient demonstrated improved hip range of motion, resolution of the limp, and radiographic evidence of enhanced femoral head containment within the acetabulum. Conclusion: This case shows that varus derotation osteotomy can impart functional and radiographic improvement in an 11-year-old presenting with Herring Group C LCPD. Despite traditionally poor prognostic indicators, advanced age and disease severity should not be considered absolute contraindications to surgical containment. Further research is indicated, considering the idiopathic and multifactorial etiologies associated with LCPD. Patient selection criteria should be refined and incorporate a wide array of presentations.