ON SUB MAINS #9 HDG #12 BLOCK, AN EMPLOYEE WAS ATTEMPTING TO PICK UP THE MINER CABLE FROM THE MINE FLOOR TO MOVE IT, WHEN A ROCK FELL FROM THE MINE ROOF HITTING THE EMPLOYEE IN HIS LOWER BACK CAUSING A BROKEN VERTEBRA. THE EMPLOYEE HAD VISUALLY EXAMINED THE AREA BEFORE ENTERING AND NO BAD TOP WAS NOTICED.