EE OPERATING A CAT LOADER PULLED UP TO THE FEEDER BIN & DUMPED. BEHIND HIM GOING TO HIS LEFT WAS A 2ND LOADER, WHICH PULLED IN TO THE BASE COURSE PILE. THE INJURED OPERATOR SAW THE OTHER LOADE R START TO BACK UP & APPLIED HIS HORN.THE OTHER LOADER STOPPED QUICKLY BUT BUMPED THE LOADER AT HIS RIGHT REAR STEPS, BENDING THE BRACKET. INITIALLY DENIED TREATMENT BUT LATER REQ. MED.9/25/0