Unknown option 'where' specified

Currently I have 2 menus, a top and a bottom, set up as separate Category sections so they can be displayed separately. But to avoid confusion, I want to set up only 1 menu section and have a list field named "Position" and be able to select either Top or Bottom.

This is all fine, except the getCategories function doesn't support the 'where' option. I get this error if I use the 'where' option:
Unknown option 'where' specified

This is my code:
list($categoryRecords, $selectedCategory) = getCategories(array(
'tableName' => 'menu',
'categoryFormat' => 'showall',
'where' => 'position="top"',
));

Is this at all possible? My other option would be just to query the entire category section and just do an if statement for the top and bottom menus... for example, for the top menu, I would do something like this.

//top menu
foreach ($categoryRecords as $categoryRecord):
if ($categoryRecord['position'] == "top") {
//display item
}
endforeach;

But I'd really prefer a more graceful solution.

/atomicrabbit