Yes you can grind cinnamon sticks in a Vitamix using the dry blade.
As long as you use the dry blade in the Vitamix you can easily grind the cinnamon sticks using the Vitamix and it will grind the cinnamon sticks in a fine powder.
You could also break up cinnamon sticks and put the cinnamon sticks in a coffee grinder which I've done before.
The coffee grinder also works great at grinding cinnamon sticks but if you have a Vitamix it works great at grinding cinnamon sticks as well.
A blender could also grind cinnamon sticks but the Vitamix or coffee grinder would work better at grinding up cinnamon sticks.