Osteoid osteoma of the femoral neck causes deformity in children: a case report.

Intra-articular osteoid osteoma (IAOO) is rare and non-specific both in clinical and radiographic presentations, thus often associated with delayed diagnosis. Synovitis and muscle atrophy occur in adult IAOO. Bony deformity can occur in children and has been ascribed to muscle contractures. We report a case of a child with IAOO in the femoral neck. There was an absence of muscle contracture during surgery, and therefore the femoral deformity may have been induced directly by IAOO in the early stage of the disease.