Measurement and resection of tumor region. A) The distance between the proximal end of the tumor located in the medullary cavity of the left distal femur and the femoral intercondylar notch was about 66.4 mm. The orange-red area represents the 3D morphology of the tumor region. The distance from the proximal end of the tumor (yellow dotted line) to the planed excision point (orange dotted line) was 50 mm. Thus, a total of 116.4 mm of the distal femur was to be removed. B) Auxiliary template to guide tumor resection.