How to rewrite URL of the question page to default URL if the user edits keyword manually?

Question

Hello, 

This is my question page.  http://www.mysite.com/q/818/searching-for-some-answer.

If I edit this url to http://www.mysite.com/q/818/something-else, it takes me to same page, because I haven't changed the questionId, but URL remains the new edited one. I want it to rewrite the URL to original one and don't retain edited url tags.

ie, even if I enter http://www.mysite.com/q/818/something-else, it should take me to http://www.mysite.com/q/818/searching-for-some-answer . How can I do it? Stackoverflow is already doing it. How to do it in Q2A? 

Any help would be highly appreciated. 

Thanks.