EMPLOYEE HAD BEEN DRIVING TRUCK IN THE QUARRY AND DUMPING ROCK INTO THE CRUSHER. WHEN THE CRUSHER PLUGGED, HE ATTEMPTED TO BAR OUT LARGE ROCK. THE ROCK SLIPPED AND PULLED DOEN HARD ON THE BAR. HE HUNG ON TO PICKER HANDLE AND WAS PULLED FORWARD. THE FORCE EXERTED ON THE HANDLE DISLOCATED HIS SHOULDER.