A friend of mine used his pinky and ring finger to open the door of his pickup truck. But it was frozen shut and he snapped the tendons (ligaments?) and that was that, he couldn't curl them shut on his hand anymore.
It's way easier to repair a "snap" than a "slice". However, you do have to get to the surgeon before 14 days are up because everything starts shrinking immediately. If you don't, then they have to graft a piece of vestigial tendon from your arm (apparently about 85% of people have it) to make up the length.