De or het routineoperatie?

The correct Dutch article is:

de routineoperatie

Rule Words ending in -tie and -sie: almost always de. See the rule

How to use routineoperatie

the routineoperatiede routineoperatie
this routineoperatiedeze routineoperatie
that routineoperatiedie routineoperatie
our routineoperatieonze routineoperatie
your routineoperatiejouw routineoperatie
every routineoperatieelke routineoperatie
which routineoperatie?welke routineoperatie?
a big routineoperatie / the big routineoperatieeen grote routineoperatie, de grote routineoperatie