Impact of pathological fracture on treatment of pediatric bone sarcoma by Anna V. Petrichenko, Kazbek F. Savlaev, Ilya A. Shavyrin, Boris V. Kurdyukov, Pavel A. Romanov, Natalya Yu. Serova, Sergey O. Nikishov, Olga A. Tiganova, Denis V. Kovalev, Alexander A. Ochkurenko, Alexander K. Morozov, Nadezhda M. Ivanova