Megaprosthesis Total Knee Replacement Following Resection of Extensive Osteoblastic Osteosarcoma in the Distal Femur: A Case Report.

Osteosarcoma is the most common type of primary bone cancer, which usually appears in the distal femur. The diagnosis of this condition typically involves advanced imaging and tissue biopsy, as well as taking into account characteristic clinical and radiographic indicators. The treatment approach for distal femoral osteosarcoma is multidisciplinary and involves initial chemotherapy, followed by limb-sparing surgery, reconstruction of bone and soft tissue, and subsequent adjuvant chemotherapy. We present a case study of a 25-year-old male admitted with a blastic lesion in the distal femur, confirmed via open biopsy to be osteoblastic osteosarcoma. Further evaluation revealed multiple pulmonary nodular lesions, managed with chemotherapy. After four months, regression of the lesion was observed. Due to malignant clinical and imaging features, excision of the lesion and subsequent reconstruction were performed, utilizing a custom-made total knee arthroplasty. The excision encompassed the removal of the distal 14 cm of the femur, with histological examination confirming central osteoblastic osteosarcoma. Satisfactory outcomes were observed during a one-year follow-up, indicating promising results. Vigilance is crucial, especially in young patients with surface-type bone tumors, as this neoplasm requires consideration.