This is my write .htaccess file.
Hope it can help you!
[code]
RewriteEngine On
RewriteRule ^(.*)-t([0-9]+)\.html http://forum.cityofsteam.com/index.php?topic=$2.0 [R=301]
RewriteRule ^topic([0-9]+)\.html http://forum.cityofsteam.com/index.php?topic=$1.0 [R=301]
RewriteRule ^topic([0-9]+)-([0-9]+)\.html http://forum.cityofsteam.com/index.php?topic=$1.$2 [R=301]
[/code]