A few months ago, my oldest son injured his two arms while iceskating. Yesterday morning, he fell strongly on hard and icy snow during his snowboard lesson (weather conditions were bad), and broke his left arm. We spent the afternoon in the hospital, where the fracture was set, and the arm nearly fully covered by a big plaster. Fortunately, no surgery was needed although the bone displacement was important.

I think he definitely has to avoid activities where the probability of falling and using the arms to prevent the fall is important. Or we have to find a way for him to learn how use his arms correctly when falling...