Further to this incident: Z has somewhat more movement in his arm, so that's good news. He worked at home yesterday and managed to slowly get his shoulder moving a little. He has recovered some range of motion, but still needs some assistance with things like socks. He went in to the office for a while today as he has a face-to-face meeting and has some things to bring home before the holidays.
He has an appointment with an orthopedic surgeon tomorrow first thing in the morning, so we'll get further insight into what happened, and what kind of treatment he needs. My guess is that it will likely be physiotherapy of some sort.
The "good thing" is that he has booked off until January 5 so that will give him time to rest and recover. We'll have a nice relaxing holiday.