The default decorator for the Zend_Form_Element_Radio is
i've create a custom view helper named MyLib_View_Helper_FormRadio (so it's called automatically if your bootstraping does so), and overrode and changed the Zend_View_Helper_FormRadio::formRadio() method at Line 160 (Version 1.11), where the radio button is created.
$label = '';
// Wrap the radios in labels
$radio = '_htmlAttribs($attribs)
. $endTag;
if ('prepend' == $labelPlacement) {
$radio = $label . $radio;
}
elseif ('append' == $labelPlacement) {
$radio .= $label;
}