Express app.get() creates new virtual directory - I don't want that

I just changed my routing from query-strings to a kind of restful API.

Before:

http://www.server.de/?item=1234

After:

http://www.server.de/item/1234

I route these requests with Express as follows:

app.get('/item/:itemID', function(req, res){
    var itemID = req.param('itemID');
    res.sendfile(__dirname + '/public/application.html');
});

Every file, that application.html wants load (like styles, images, javascripts ...) is saved in a subdirectory assets/... After the routing-change, they are being searched in the "virtual" directory item/assets/... which of course returns 404 (until I change the paths in the .hmtl-file).

How can I route such URLs without changing the whole context of paths?

Edit:

Watch Tim Coopers comment. Redefining the paths in the .html-file as absolute did the trick.