It's appropriate depending on the type of break and where it is located. My husband broke his wrist and was in a cast up to the shoulder. Then, they replaced that cast with one that was up to his forearm after about 3 weeks. He was in a cast for a total of 7 weeks altogether for the break to heal. It's all about stabilizing the bones and preventing movement that will compromise the healing process. I seriously doubt the full-arm cast will be left on the whole time. They usually cut them down mid-way through the casting plan. I had the same thing but on my foot. I tore the plantar fascia ligament in the arch of the foot and I was casted up to my knee! YIKES! It was all about making sure I did not flex or rotate my foot by way of the calf muscles and ankle. It worked. I'm all better now!