I think it is called a premises injury lawsuit. And he's suing both the owner of the premises and the chair manufacturer. If liable, there would have to be some sort of allocation of responsibility. A few years back a Canadian sued a NYC fast food joint for his "member" being severed by a toilet seat shifting and crushing his "manhood."
Tennessee just offered a helping hand.
I'll see myself out.
Don't ask questions that you do not want answered.