Showing Post level info at the thread level

I have a forum where only the person who starts a thread can reply to it. Effectively every thread has one author. So I am trying to streamline the display.

When displaying a thread, I would like to display what would typically be in the postbits templates, once and only once at the top of the page. For instance I would like to have the users title and avatar at the top of the thread... probably in the table header bar. However, if I use variables like $post[joindate] at the showthread template level, it doesn't resolve correctly. Can anyone think of a quick workaround?

Here is a small portion of the showthread template that I want to change. This works:

PHP Code:

<td width="100%"><normalfont color="#EEEEFF"><b>$thread[title]</b><font color="cyan"><br>
by $thread[postusername]</font></normalfont></td> 


this doesn't work (look at the second half of the second line):

PHP Code:

<td width="100%"><normalfont color="#EEEEFF"><b>$thread[title]</b><font color="cyan"><br>
by $thread[postusername]</font><br><br>$post[avatar]</normalfont></td> 


Do people get what I'm trying to do?