Doing a Bankhead in a restraint chair
The Bankhead Bounce is a dance move that originated in the poor neighborhood in Atlanta that southern rappers like T.I., Dem Franchize Boyz, and Shawty Lo call home. A restraint chair is what they tie insane people into when they are a danger to themselves or others (think Hannibal Lecter in Silence of the Lambs). So by saying that he is able to do this dance move even while tied down, Em implies that he is batshit crazy for even attempting this but also incredibly skilled since he can pull it off.
To help improve the meaning of these lyrics, visit "Rhyme or Reason" by Eminem Lyrics and leave a comment on the lyrics box