Distal Femoral Osteosarcoma: Multimodality Imaging Findings and Surgical Correlation with Van Nes Rotationplasty

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Osteosarcoma is the most common primary malignant bone tumor in children and adolescents and most frequently arises in metaphysis of the long bones, particularly around the knee.Imaging has a central role throughout the clinical course, from initial diagnosis and staging to assessment of treatment response, surgical planning, and postoperative surveillance.We present the case of an 11-year-old girl with distal femoral osteosarcoma treated with neoadjuvant chemotherapy, wide surgical resection, and Van Nes rotationplasty.Initial radiographs demonstrated an aggressive mixed lytic and sclerotic metaphyseal lesion with cortical destruction and aggressive periosteal reaction.Magnetic resonance imaging demonstrated extensive intramedullary involvement with cortical breakthrough and a large extraosseous soft-tissue component, without neurovascular encasement or definite intra-articular extension.Whole-body bone scintigraphy and chest imaging demonstrated no evidence of additional disease.Following neoadjuvant chemotherapy, MRI demonstrated decreased soft-tissue enhancement and increased areas of nonenhancing tissue.Histopathologic examination of the resection specimen demonstrated greater than 90% tumor necrosis.Van Nes rotationplasty was selected as a durable limb-salvage reconstruction, with the primary goal of maximizing long-term mobility in this skeletally immature patient.Postoperative radiographs demonstrated satisfactory reconstruction and progressive osseous consolidation.At more than 5 years of follow-up, the patient remains free of local recurrence and distant metastatic disease.This case illustrates the complementary contribution of radiography, bone scintigraphy, MRI, and postoperative imaging in pediatric distal femoral osteosarcoma and demonstrates the role of imaging in following the patient from initial diagnosis through long-term surgical reconstruction.