EMPLOYEE ALLEGES HE WAS JACKHAMMERING ON A CURNER PIPE THAT WAS SITTING ON SAW HORSES. A CASTABLE CAME OFF THE PIPE CAUSING THE BURNER PIPE TO ROLL OFF OF THE HORSES TOWARD HIM. IT FELL STRIKI NG HIS RIGHT SHIN. HE HAD THE HAMMER IN HIS LEFT HAND AND WHEN HE PULLED BACK TO GET OUT OF THE WAY HE FELT A CHARLIE-HORSE IN THE LEFT SIDE OF HIS LOWER BACK.