htaccess rewrite help

I'm using smf forum currently and am in the middle of wrapping Joomla around it using a bridge. However there are 50k posts/urls that are indexed in the search engines and hope to keep them there. So I'm trying to rewrite the new urls to render the old ones... just for the forum section which as you'll see uses the syntax: option=com_smf.

I need to change the url:
index.php?option=com_smf&topic=1.msg2#new

to this:
index.php?topic=1.msg2#new

How would I write this in the htaccess file?

 

Try with this:

RewriteEngine on
RewriteBase /
RewriteRule   ^index\.php\?(option=com_smf&)(.*)       /index\.php\?$2

Code (markup):

 

that didn't work.

I should mention that msg2 is dynamic, msg3, msg43 etc.

 

Search for option or com_smf in the file and edit the link code.