I'm trying to think of what muscle group would be used in rotating your arm up. Maybe the deltoid? Don't know for sure.
It just seems like a muscle issue. You have no strength to rotate that forearm up, but you can easily push it up with your other arm.
Finally, did your Dr. tell you a RSR was possible? That seems like a big decision to make if you didn't know it could be coming.
I have arthritis in both shoulders, one of them produces pain and cortisone shots help a lot. I may get it replaced in the future, and as my rotator cuff is intact, I expect that would be an anatomically-correct TSR, not an RSR. I'm not sure I'd have an RSR, but I certainly would like to know if that might be necessary.
Again, this looks like total loss of the muscle responsible for rotating your arm up.
I'm sorry for what you're going through and hope you can get some answers. All the best to you young man.
Yes it is the deltoids that help to raise your arm,especially if rotator cuff is not good. I am 12 months postoperative after trust and still cannot touch the middle of the back of my head and am not driving. My surgery was done because of fractures and surgeon said outcome is not always as good as it would be for arthritis. I had a nerve test done to make sure that was not the issue,but it was not. I will keep exercising and now am doing light weights ,for deltoids,which was not suggested at the 2 pt places I went to.
I am hoping Fredhas made more progress and never give up .