EMPLOYEE WAS HITTING ON TRACK PIN WITH A 16LB SLEDGE HAMMER WHEN A PIECE OF THE PIN BROKE LOOSE. THE BROKEN PIECE HIT HIM JUST ABOVE LEFT KNEE, LODGING NEAR HIS FEMUR BONE. (NOTE: THIS WAS INITIALLY CHARGED AS A FIRST AID CASE, HOWEVER 4 DAYS LATER HIS DOCTOR DETERMINED THAT METAL NEEDED REMOVED)