Vertical Chin Reduction
You need a sliding genioplasty to allow the chin bon to be moved forward and at the same time become vertically shorter. How much vertical shortening and horizontal increase remains to be determinejd by preoperative computer imaging.
Shortening the long chin
A long chin can be shortened using an osteotomy and by removing a horizontal segment with or without moving the chin forward through an incision inside the mouth. You have a vertical macrogenia according to the classification that I have developed. This could make he entire face long. The surgery is an outpatient procedure under general anesthesia and take about 30 minutes. This surgery would not change your bite. Rarely, depending on the shape of the chin the bone can be shaved down through an incision under the chin. Without a front view picture it would not possible to judge whether the latter operation would be appropriate for you.
your facial development pattern is called 'high angle' and leads to the 'back part' of the jaw being short and the body of the jaw being long. This increases the face height and usually the jaw is 'narrow/slim' looking frontally. You can alter the overall appearance with augmentation of the 'back' area and a sliding genioplasty.