Partial palm, 4th, and fifth digit tingling began 10 weeks post rotator cuff surgery. 6 weeks later no change. what is the connection? what to do?

Brachial plexus: The shoulder joint is nearby the brachial plexus, and perhaps some nerve stretching occurred, during rehab, but the problem might be at the elbow instead. Either way sounds in an ulnar nerve location. An EMG might help. See your doctor, as there very likely is some connection.

Let me explain: To tingling in those fingers could be from three sources in your case. From the surgery site or from the neck area and could from the elbow level. It is not from the surgery site because did not happen after the surgery. I believe from the neck area in form a disc problem. Or could pressure on the nerve of the inside the elbow.

Cubital tunnel synd: You were in a sling after rotator cuff surgery and you most likely had swelling in the arm. These two things has caused you to have irritation on the ulnar nerve at the elbow (funny bone). You need to see a hand surgeon before you have permanent damage.