Limb-salvage surgery in the treatment of osteosarcoma in skeletally immature individuals. Sacrifice of major growth plates during resection and fixed-length reconstruction of a limb in a skeletally immature child with osteosarcoma may result in a significant limb-length inequality as growth progresses. A limb-length discrepancy in the humerus may cause minor cosmetic problems but does not generally result in a significant functional deficit. In the lower extremity, tumors about the knee, including the distal femur and proximal tibia, usually present the dilemma of whether limb salvage by arthrodesis, osteoarticular allograft, or endoprosthetic replacement would result in a significant limb-length inequality and whether amputation of the extremity is a preferable procedure. The techniques of rotationplasty and an expandable endoprosthesis have been successfully used for treating skeletally immature patients with osteosarcoma of the distal femur. With regard to survival and function, the results obtained with these innovative methods are favorable compared with those of a high above-knee amputation. 