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 .