I have never broken a bone anywhere on my body, except when the surgeon broke my breastbone in two to get at my heart. It's really amazing that in 15 years of chimney work and scaffold setup, teardown and working on it 30-50 feet in the air, plus scaling dangerous roofs nearly every day I never had a serious injury. I only fell twice, and only from 10 feet and walked away with my butt and ego bruised but that's it.
I hope your co-worker regains the use of his arm (don't I know how limited use of arms is like), and worker's comp comes through big time for him.