andreaamado on "Other posts pagination inside post"

How can I show in post page, a box with posts from other specific category, with pagination?
I can show a box, but i can’t do a pagination. It doesn’t works.
Ex.:

<?php
        global $wpdb;
        $total = "SELECT post_title AS titulo, ID AS idPost, guid AS url
                  FROM wp_posts
                  WHERE post_status = 'publish'
                  AND post_type = 'post'
                  AND post_author = $getAuthor
                  ORDER BY post_date DESC";
        $totalposts = $wpdb->get_results($total, OBJECT);
        $ppp = intval(get_query_var('posts_per_page'));
        $wp_query->found_posts = count($totalposts);
        $wp_query->max_num_pages = ceil($wp_query->found_posts / $ppp);
        $on_page = intval(get_query_var('page'));
        if ($on_page == 0) {
            $on_page = 1;
        }
        $offset = ($on_page - 1) * $ppp;
        $wp_query->request = "SELECT post_title AS titulo, ID AS idPost, guid AS url
                              FROM wp_posts
                              WHERE post_status = 'publish'
                              AND post_type = 'post'
                              AND post_author = $getAuthor
                              ORDER BY post_date DESC
                              LIMIT $ppp OFFSET $offset";
        $pageposts = $wpdb->get_results($wp_query->request, OBJECT);

        if ($pageposts) {
            global $post;
            foreach ($pageposts as $post) {
                setup_postdata($post);
        ?>
                <div class="catMedicos">
                    <a href="<?php echo get_permalink($post->idPost); ?>"><?php echo $post->titulo; ?></a>
                </div>
        <?php
            }
        }
        ?>
        <?php if (function_exists('wp_pagenavi')) wp_pagenavi(); wp_reset_postdata(); ?>