Ouch that sucks. Well I also fractured my arm (well actually wrist) about a year ago. You know how when you move your arm in certain ways like twisting it you would feel pain, (thats how you were probably able to tell something was wrong with it and got an X-ray) well I constantly kept moving my arm like that. If the pain got worse, then I lowered the weight assuming I was going too heavy for the fractured arm to handle. I also took a calcium supplement.
I did an entire workout last night and it feels ok, a little soreness but I think that may be from lack of use. Thanks for the tip on the Calcium though.