EE WAS OPERATING MACK TRUCK #12 PULLING AN ALUMINUM DUMP TRAILER. THE TAIL GATE ON THE DUMP TRAILER WAS STUCK SO EE STRUCK HIS HAND INSIDE OF BOTTOM OF GATE AND PULLED. THE BOTTOM PART OF GATE INITIALLY OPENED THEN JERKED BACK, CATCHING EE 'S HAND BETWEEN GATE AND TRAILER. EE S RIGHT LITTLE FINGER WAS DIAGNOSED WITH A FRACTURE AND A LACERATION.