get_posts() JOIN another table ?

My site use WooTheme and I want to display popular posts on Popular tab within WooTabs Widget as Most Read Posts in a week, not as Most Comment Count by default.

Here’s the default code of WooTabs’s Popular Tab:

if (!function_exists('woo_tabs_popular')) {
	function woo_tabs_popular( $posts = 5, $size = 35 ) {
		global $post;
		$popular = get_posts('caller_get_posts=1&orderby=comment_count&showposts='.$posts);
		foreach($popular as $post) :
			setup_postdata($post);
	?>
	<li>
		<?php if ($size <> 0) woo_image('height='.$size.'&width='.$size.'&class=thumbnail&single=true'); ?>
		<a title="<?php the_title(); ?>" href="<?php the_permalink() ?>"><?php the_title(); ?></a>
		<span class="meta"><?php the_time( get_option( 'date_format' ) ); ?></span>
		<div class="fix"></div>
	</li>
	<?php endforeach;
	}
}

I try to find a plugin to record post hits and I installed “Most Read in XX Days”.

This Plugin create a table named “most_read_hits”:
(ID, post_ID, hits)
and any post read count within a number of days will be recorded in to “hits” field.

Now I want to use the “hits” field in “most_read_hits” to get and order some posts get from get_post() (Edit the code of “WooTabs Popular Posts” above.

I tried to edit
$popular = get_posts('caller_get_posts=1&orderby=comment_count&showposts='.$posts);
to
$popular = get_posts('caller_get_posts=1&join="JOIN $wpdb->most_read_hits ON $wpdb->posts.ID = $wpdb->most_read_hits.post_ID"&orderby=$wpdb->most_read_hits.hits&showposts='.$posts);
but it only lead to displaying latest posts.

Anyone help me solve this?
Thank you!