SHUTTLE CAR OPERATOR WAS LEAVING THE MINER WITH HIS BUGGY LOADED WITH COAL. AS HE MADE A LEFT TURN, THE WHEEL UNIT ON THE DUMPING END, REEL SIDE OF SHUTTLE CAR BROKE OFF. THE BUGGY STOPPED ABRUPTLY CAUSING THE OPERATOR TO PITCH FORWARD & TO THE LEFT. THIS CAUSED HIM TO STRIKE THE LEFT SIDE OF HIS HEAD INTO THE CONTROL AREA OF THE SHUTTLE CAR.