No one injured Cena (who I'm guessing is this Captain Retard who puts his health on the line that you are WISHING SERIOUS HARM upon) - Cena did his goofy little hiptoss and screwed his arm up. Kennedy might've sandbagged him on it (something he loves to do), but it's impossible to tell if that was the case looking at the footage.
Anyway, that was an absolutely insane move, and I'm glad that WWE not only showed A TON OF REPLAYS (take note, TNA), but drove home how dangerous it was (again, take note TNA), and showed both men being injured by the move (again, take note TNA). Should they have saved it for PPV? Possibly, but it was a memorable live moment, something that will likely be replayed many times, and something that added even more fuel to what has so far been a fantastically built WWE title match at the Rumble.