Employee was operating a battery ram car. He stated at the end of his shift that he bumped his head on the canopy. He continued to work until 1/16/12 when he went in for surgery to repair L5 b ulged disc. Doctors report indicate that he had inter vertebral disc disorder in 2009 and mild degenerative changes, mild disc desiccation at L4-5 at the time he bumped his head.