Talk to Pediatrician on Erb Palsy

My son aged 6 Month. There was no movement in his left arm when he born, I asked gynecologist she told me it was normal and during delivery there was no problem. Very next days he was diagnosed manengides and immediately admitted in children's hospital, after 15 days treatment he was fit but his arm was dead, we talked to Doctors and they refferes to Physio Therapist, he gave us hope that his hand will recover within 2 or 3 years. Now his arm is moving up to wrist. Still there is no movement in fingers. We r visiting Physio Therapist continuously and consistently.... Any suggestion or recommendations. Thanks.