NFL Draft 2011 Traded Pickshttp://www.draftinsiders.com/node/35
The pick for Justin Tyron has been described as conditional. It seems to be between the respective front offices what the conditions of the trade were. There are no clues when searching for Indianapolis or Washington at the above links.
Tryron made 6 starts for the Colts in 2010 and all indications are that he made significant contributions to their team. Perhaps the success of the Colts in the playoffs may be part of the conditions in this trade.