Symmastia is a condition where the two breasts merge together across the midline of the chest, eliminating the natural separation known as the intermammary cleft or cleavage. The term is derived from Greek roots meaning “breasts together.” This anatomical change results in the appearance of a single, continuous breast mound. While not typically a medical risk, the condition often leads to cosmetic concerns and emotional distress for those affected.
Anatomical Description and Appearance
The normal anatomy of the chest wall features a distinct boundary at the sternum, the bone that runs down the center of the chest. Connective tissue and skin adhere firmly to the sternum, creating the defined space between the medial boundaries of the breasts. In symmastia, this natural structure is compromised, allowing breast tissue or, more commonly, breast implants to cross the midline.
The physical manifestation is often described colloquially as a “uniboob” or “bread loaf” appearance. Instead of two distinct breast mounds separated by a defined cleavage line, there is a continuous web of skin, fat, or tissue bridging the space. The severity can vary, from a slight reduction in cleavage to an almost complete fusion.
Symmastia is defined by the loss of the skin’s adherence to the breastbone, not merely the breasts touching due to large size. This loss of definition can lead to an unstable feeling; implants, if present, may visibly shift together when a person lies down or rolls onto their side. The resulting visual distortion is the primary concern for those seeking correction.
Congenital Versus Acquired Causes
Symmastia presents in two main forms: congenital and acquired, also known as iatrogenic. Congenital symmastia is exceedingly rare and occurs naturally from birth due to developmental anomalies. While the exact mechanisms are not fully understood, some evidence suggests a genetic component involving an abnormal arrangement of collagen fibers that causes poor tissue adherence to the chest wall.
Acquired symmastia is the more common form, developing most frequently as a complication following breast augmentation or reconstruction surgery involving implants. This complication arises from the over-dissection of the medial breast pocket, which is the space created to hold the implant. If the surgeon dissects too far toward the midline, they can inadvertently disrupt the attachments of the pectoral muscle and the skin to the sternum.
Over-dissection allows the implant pockets to communicate across the midline, enabling one or both implants to migrate inward and eliminate the cleavage. Another significant contributing factor is the use of implants that are too wide or too large for the patient’s specific chest anatomy. Oversized implants exert excessive pressure on the weakened medial tissue, causing it to detach from the breastbone and allowing the implants to merge.
Options for Correction and Treatment
Established symmastia almost always requires revision surgery to restore the natural cleavage. The primary goal of surgical correction is to reconstruct and reinforce the midline barrier that normally separates the breasts. The surgeon must temporarily remove the existing implants to access and repair the compromised internal tissue.
A common technique is capsulorrhaphy, which involves tightening the internal capsule (the scar tissue surrounding the implant) using internal sutures to create a new, stable medial boundary. Surgeons may also use suture plication, where the soft tissue and capsule are sutured directly to the periosteum, the membrane covering the sternum, to anchor the tissue in place.
In some cases, the repair is reinforced using advanced materials like synthetic mesh or a dermal matrix, which acts as an internal bra to provide long-term stability and prevent recurrence. If the original cause was an implant that was too large, the revision procedure will often involve replacing the implant with one that is appropriately sized for the patient’s chest width. In mild or early cases of acquired symmastia, non-surgical management, such as the consistent use of a specialized compression bra or band, can sometimes be successful by pushing the cleavage skin against the breastbone to promote re-adherence.