Wordpress Permalink Structure /post/post_id/anything-goes-here

I'm trying to setup a permalink structure like so 'http://ift.tt/1yFK4Ye'. Which is kinda similar to how SO's permalinks to questions work. If the last part is changed it still loads the right page as long as the first part contains the correct question ID. I'm not sure if it's redirecting or pushing the question title back into the URL when you do that though.

I've tried /post/%post_id%/%postname%/, but that requires the correct post title in the url. I want that portion to not matter, but still have the flexibility in being able to place a title in it.

I'm guessing some server configuration changes may be required. I'm running NGINX.