I do know my doctor debated it aloud for a moment or two before deciding on a cast, and I was still too freaked out over the whole thing to ask him any questions about it.
They did put me in what is called a "Munster cast" - it goes from my elbow to up around the space between my thumb and forefinger, then they cut out a piece at the elbow leaving a "wing" on either side. This allows me to flex my elbow, although not to straighten it fully, and it prevents me from rotating my forearm. I've tried to make a point of flexing and straightening my fingers repeatedly throughout the day, but even with that, I've felt them growing gradually stiffer over the weeks.
I don't even want to think about what my wrist is going to feel like when the cast finally comes off for good!