Re: acromioclavicular joint
Not sure what impression means unless they mean images. I separated my ac joint which is the joint you mentioned. The joint itself is soft tissue so x-ray probably won't tell the whole story. There are many websites that describe the shoulder anatomy. The clavicular joint is your collar bone and the acromion is the bone it attaches to near the shoulder. If you follow your collar bone towards the shoulder the acromion is where the little bump is on top of your shoulder. If you haven't been to an orthopedic doctor I would see one. He may refer you to physical therapist or ortho surgeon.
I have done a lot of research since my injury as I am still having problems.
I highly recommend to get first hand experienced from former patients of specialists to help selecting a specific doctor. Ask people you trust who either went themselves or have close friends/relatives who had successful treatment. I hope this helps.