It is active assistive range of motion exercise
Place your hand of your surgical side on a wall, and walk your fingers the wall. Start gentle, then gradually walk up the wall until you feel a stretch.
You can then walk your hand back down a bit, relax, then go back up again. As your tissues warm up, you may be able to get your arm up further. Walk your arm back down.
Do this exercise with your arm straight out in front of you.