Congenital symmastia repair, is this a possibility for me?

I have had the opportunity to help several patients with this condition; I often combine liposuction surgery of the pre sternal area with breast augmentation surgery. A second stage operation (capsulorraphy) may be helpful in improving the “definition” of the medial breast border (cleavage) if necessary. You may find the attached link, dedicate to symmastia surgery concerns, helpful to you as you learn more. Best wishes.

Congenital symmastia are a difficult condition to treat. They can fixed by internal stitches to improve the results but it's advisable to go for these if you going for an implant based operation . quite often there is recurrence of the symmastia in post operative period. simple augmentation procedure can make the condition worse at times. It is advisable to see a plastic surgery consultant who can examine and give you honest opinion on further management

There are several techniques to help this prominence of tissue between the breasts.  A picture would really help propt some options.  There are issues with prominent fat deposits over the breast bone that can be addressed with liopsuction.  You already have large breast so a procedure that narrows and lifts the breast can change the cleave area.