EE WAS ATTEMPTING TO REMOVE A BRASS RIFLE NUT FROM A QUARRY BAR PISTON IN THE SHOP. THE PISTONWAS IN A VICE, EE WAS PULLING WITH A TOOL AND A CHEATER PIPE, NUT CAME LOOSE AND THE EE LOST HIS BALANCE, FELL BACKWARDS ONTO HIS LT. LEG & BROKEBONE IN LOWER LEG.