Except in rare occasions loss of upper pole fullness cannot be restored without an implant. Now you stated that you don't want to be any larger so this can be somewhat difficult to achieve.
When a mastopexy is performed the nipple/areolar complex is elevated by removing excess skin. Sometimes in heavier patients enough breast tissue is moved superiorly to help augment the upper pole. Unfortunately, this is less common than you'd think. So to replace that fullness you'll need an implant.
Now implants are really based on breast base width. If your base width is 12cm than you can get away with an implant that is anywhere from 10.5-13.5cm. Then depending on the style of implant depends on the volume. Yes, it's complicated but that's why Plastic Surgeons have charts etc. to help. In these circumstances I usually use a low profile implant with as little volume as possible for the breast width.
So it's likely you'll get some increase in size but your breasts will look fantastic so be open minded.
