I arrived at this conclusion in the negative direction. My arms aren't neither especially large nor especially muscled, but even so my right arm has shrunk noticeably when compared to my left. I noticed it at least two weeks ago, and the orthopedist commented on it at my appointment last week. (I'm not sure if he meant it as a cautionary tale to compel me to go to physical therapy, an attempt to reassure me that physical therapy would improve the situation so i shouldn't worry, or if he was just surprised at the difference.)
However at this point it's been about six weeks since the original injury, and when i first started noticing the difference it was only about four weeks. So on the one hand you can lost muscle mass pretty fast when those muscles are mostly incapacitated. However on the other hand (er, so to speak) it's not like my left arm has actually been doing that much work. Obviously i haven't been going rock climbing, i haven't been going to the gym, and i haven't been going rollerblading (except for that one night at Wumpskate, and even then it wasn't the whole night, and i wasn't wearing my wrist weights.)
So my left arm has maintained its muscle tone (at least compared to the right arm) just through trivial daily tasks. Carrying bags, opening doors, bathing, eating, typing, etc, which is both weird and kind of impressive.
As long as i'm talking about injury stuff though...
I fractured the left side of my wrist, so i expect pain there. The surgery was on the bottom of my wrist, so i expect pain there. Given the locations of tendons and stuff and the lack of use to which they've been put i can even understand pain on the right side of my wrist.
But why have i been getting intermittent deep aches in the center of the top of my hand? It seems to be along or in between the "finger" bones that run the length of your palm, not the cluster of lumpy bones at the base of the hand.
The muscle at the base of my palm, the one that leads into my thumb, has also been rather sore, but that's understandable given how it also saw some shrinkage and is finally getting some exercise again.
I've also started getting pretty strong aches in my wrist and right below it, in the areas where either the bone was broken or spikes for the plate were driven in, so i'm assuming that's a perfectly natural part of the healing process. In a lot of ways it's actually more annoying than the pain from the original fracture was. After the initial bit that just hurt when i moved my wrist wrong, so i could make it stop by just not moving. The ache is a lot less strong but it starts and stops on its own and there's nothing i can do to influence it. (Well, other than take drugs of course =)
On a not-very-different note, i need to come up with some kind of injury icon. Although by the time i get around to doing that it may be irrelevant :)