Abstract: Fibrous dysplasia of bone is a skeletal disorder,characterized by the replacement of the bone marrow organ with a tissue formed by pre-osteogenic fibroblast-like cells and trabeculae of immature bone.The proximal femur is most commonly affected and prone to hip inversion with proximal femoral curvature,as well as "Coxa Vara" deformity,making surgical correction difficult.This article introduces a case of proximal femoral torsion caused by fibrous structural defects admitted to the Orthopedics Department of Kunming Children's Hospital.Fassier Duval extended intramedullary nail combined with Kirschner wire was used for one-stage osteotomy correction of the deformity.The case was followed up for 24 months after surgery,and the corrective effect remained good.

Key words: fibrous dysplasia, coxa vara deformity, osteotomy, children