The problem could be a number of places, in what I call the nueomuscular line that works the arm system. The line got a big shock which will have affected it. I would guees its the upper 4th and 5th vertabrea and muscles that surround the said, have tightened up stopping the messages from the spine communicating with the arm and shoulder as they should. theres a few good stretches that would help. Pins and needles give the game away.