Yes! Even though I won’t be able to put needles into the injured area if there is a cast, I can place needles into the “healthy” arm and it will still help the broken arm heal faster. This is because almost all acupuncture channels run bilaterally on your body. If an acupuncture channel goes down one arm, it will also go down the other arm.
I have had many patients ask me why I’m putting a needle into their left arm or leg when it is the right arm or leg that hurts. With acupuncture, we often needle the opposite side of body, not always where it hurts or is injured. This technique still works because the right side of the brain controls the left side of the body and vice versa. There’s a neat little article about that here.