Periarthritis of the shoulder often causes significant stiffness of the shoulder. The pain and spasm initiates a vicious cycle restriction in movements and further increase in pain. Different remedies have been suggested for this but none of them provide complete relief or restoration of the range of movements. Manipulation has been tried but there is always a risk of producing a fracture while the limb is manipulated. Unless it is an experienced surgeon and he/she follows specific precautions to avoid a fracture I would not recommend it as a routine treatment. There are several articles in the medical literature on manipulation under anaesthesia. Different techniques of manipulation are described to avoid a fracture.
I am sure your orthopaedic surgeon would have seen some of these articles and would take adequate precautions while manipulation is being attempted.