EMPLOYEE WAS STANDING UNDER KILN TIRE #2 AIR ARCING WELD OFF OF THE KILN SHELL IN ORDER TO REPLACE WITH NEW BLOCKS. HE STEPPED UP ON A BUCKET TO GET CLOSER TO HIS JOB. THE BUCKET SLIPPED OUT F ROM UNDER HIM AND HE FELL ON HIS BACK. EMPLOYEE DID NOT SEEK MEDICAL ATTENTION UNTIL 4/14/03, WHEN HE WAS GIVEN OSTEOPATHIC MANIPULATIVE TREATMENT.