EE WAS STARTING 50 TON CAT. HE SPRAYED ETHER IN ENGINE AND WALKED AROUND FRONT OF CAB TO START MACHINE. HE PULLED ON DOOR AND IT WAS EITHER STUCK OR FROZEN AND WHEN HE PULLED AGAIN HE LOST HIS FOOTING ON THE CATWALK, DUE TO ICE AND SNOW, FELL TO THE GROUND ABOUT 7' AND LANDED ON HIS SHOULDER.