Gracias @jaziel matoso,
El siguiente código funciona:
global $wp_query;
$query = "
SELECT wposts.*
FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
WHERE wposts.ID = wpostmeta.post_id
AND wpostmeta.meta_key = 'votes'
AND wposts.post_status = 'publish'
AND wposts.post_type = 'post'
ORDER BY CAST(wpostmeta.meta_value AS SIGNED) DESC";
$total_record = count($wpdb->get_results($query, ARRAY_A));
$paged = get_query_var('paged') ? get_query_var('paged') : 1;
$post_per_page = get_option('posts_per_page');
$offset = ($paged - 1)*$post_per_page;
$max_num_pages = ceil($total_record/ $post_per_page);
$wp_query->found_posts = $total_record;
// number of pages
$wp_query->max_num_pages = $max_num_pages;
$limit_query = " LIMIT ".$post_per_page." OFFSET ".$offset;
$result = $wpdb->get_results($query.$limit_query,OBJECT);// return OBJECT
if($result):
foreach ($result as $post):
setup_postdata($post); ?>
<h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
<p><?php the_content(); ?></p>
<?php endforeach; ?>
<div class="navigation"><?php wp_pagenavi(); ?></div>
<?php
endif;
¡Listo!