Joomla custom app, matching and using alias/try_files

G'day,

Unfortunately I've only got a limited knowledge of what I'm asking, please forgive me if I use the wrong terminology (this might be why I failed to find the answer on Google).

Currently I have a Joomla site working with Search Engine Friendly URLs, using the following Joomla works great:
try_files $uri $uri/ /index.php?$args;

I'm writing a PHP script that is included inside a Joomla article that will reference the URI to generate its queries to the database, for this to work properly I will need to match all child URI's and display the parent URI (not a redirect).

As an example:
Joomla article (Parent): http://mysite.com/catalogue
Child: http://mysite.com/catalogue/shirt/short-sleeve/page1

In the above example, I would like to still see the "Catalogue" in Joomla but maintain the entire child URI... at the moment if I browse to the child url I get a 404 error.

Thanks in advance,

Brad