My breasts look joined in the middle. Is that symmastia?

If the cleavage groove is gone standing and the center joins as one mass, and lying down the implants crowd to the center and touch, symmastia is likely. Ultrasound confirming the two pockets communicate makes the diagnosis.

Will a bra or massage fix it?

No. The tissue that held the middle has detached from the sternum, so pressing from outside does not restore it and can push the center wider. It is corrected only by surgery that rebuilds the wall.

Will correction make my breasts smaller?

Often, yes. Reducing the medial space to rebuild the wall usually means a smaller implant. In an 18-case report, 4 had the implant changed again in a second stage for size. Decide before surgery where to weight size versus the groove.

Yes. In an 18-case report, 3 recurred. So it does not rely on one capsule suture: muscle and fascia are rebuilt together, the plane changed, size reduced, and post-op compression layered on.

Is augmentation itself risky with a pigeon chest?

It is a higher-risk body type, but preventable. In a Korean report of 132 patients with pectus excavatum or carinatum tendencies, not one developed symmastia. The chest angle is measured and the plan set to it.

Revision Surgery

Symmastia: Causes, Correction, Prevention

UNE Plastic Surgery · Dr. Kim Uigeon, board-certified plastic surgeon · Published 2026-09-21 · Updated 2026-09-21

After breast augmentation, some find the cleavage gap gone and the center joined into one mass. The implant has crossed over the sternum and met the other side — this is called symmastia. It is rare, but tricky to fix once it occurs. To answer first: symmastia does not resolve on its own over time, and is not fixed by a bra or massage. The tissue that held the middle has detached from the sternum so the two pockets connect, and it is corrected only by surgery that rebuilds that wall — where the design to prevent recurrence matters far more than in a first surgery. This article covers what the condition is, why it occurs, how to correct it without recurrence, and how to prevent it at the first surgery. Every clinical figure is linked to a cited study.

1. The condition called symmastia

A normal breast has skin attached to the bone over the sternum, so there is a groove between the two breasts. In symmastia that attachment is released, and skin and fat bridge across the middle like a bridge, so the two implant pockets communicate as one. Outwardly:

The cleavage groove disappears and the center domes as one mass.
Lying down, the implants crowd to the center, touch each other, or fall to one side.
A bra lifts the central skin forward awkwardly, and cinching to make a groove does not hold.

A congenitally such shape is very rare; most is acquired after breast surgery. It can arise after fillers or fat grafting too, not only implants. In a report of 18 cases, 15 were after implants and 3 after an injectable method such as filler or fat grafting (Liu et al., Annals of Plastic Surgery, 2024).^[2]

2. Why symmastia occurs

Four causes are named: over-dissecting the medial pocket up over the sternum, cutting the fascia over the sternum, an implant larger than the breast base width, and detaching too much of the pectoralis where it attaches to the sternum when placing under the muscle. A study looked at which is most common (Kalaria et al., Aesthetic Surgery Journal, 2019):^[1] all 23 symmastia cases one surgeon corrected over 10 years had had submuscular augmentation. Asked of 91 aesthetic-surgery society members, they had seen a mean of 2.2 acquired-symmastia consultations in the past year, of which 84.9% had had submuscular surgery, and most named over-detaching the pectoralis where it attaches to the sternum as the cause. So the key is how much of the tissue forming the wall between the breasts is left. Detaching the muscle from the sternum removes the wall that would block the implant, and a large implant then pushing medially makes the two pockets meet. Even when using the submuscular plane, this wall is kept by leaving the sternal attachment and releasing only the lower part.

3. Why unusual chest shapes need more care

A pectus excavatum (sunken center) and a pectus carinatum (protruding forward) have a tilted plane over the sternum, so the implant slides to the center easily — making them body types at higher symmastia risk. A Korean report organized how to operate in these shapes (Byun & Park, Aesthetic Plastic Surgery, 2023):^[3] 132 patients with a tendency to pectus excavatum or carinatum were operated over 3 years — 71.21% inframammary and 28.79% axillary incisions, mean implant volume 337 cc, mean follow-up 16 months. The satisfaction-scale score averaged 9.13, and not one developed symmastia — meaning it can be prevented by planning to the chest shape. This is why the chest is palpated and its angle measured on photos at consultation.

4. The principle of correction: rebuilding the wall

Symmastia correction re-divides the two pockets and re-attaches the central skin to the sternum. The principles the study authors organized are four:

Fix the superficial fascia to the sternum — the central skin must reattach to the bone for the groove to return.
Re-attach the detached pectoralis to the sternum — the muscle becomes a wall that stops the implant crossing medially.
Do not place it under the muscle again — the same plane lets the same force act again.
Protect the repair with a fixation device after surgery — keeping the implant from pushing the center while the repair heals.

Several methods are reported. Cutting the medial capsule in a crescent and suturing it tightly corrected 10 patients with no recurrence over a mean of 24 months (Zingaretti et al., Annals of Medicine and Surgery, 2018);^[4] a method attaching a negative-pressure device to compress the center after suturing has also been described (Lawrence et al., Journal of Surgical Case Reports, 2025).^[6] Making a new pocket in front of the existing capsule and moving the implant is another: it corrected 29 patients (52 breasts) with malposition, with no complications including symmastia at a mean 7.9-month follow-up (Qiao et al., Aesthetic Plastic Surgery, 2025).^[5] Whatever the method, the common thread is not relying on one suture: a capsule suture alone can reopen, so muscle and fascia are rebuilt together, the implant size reduced, the plane changed, and post-op compression layered on. When tissue is thin, the center is reinforced with acellular dermal matrix.

5. Recurrence and size

Honestly, this is a surgery with recurrence. In a report correcting 18 cases by various methods, 3 recurred, and 4 were dissatisfied with the breast size after correction and had the implant changed again in a second stage (Liu et al., 2024).^[2] The authors concluded that difficulty must be classified and a strategy set before surgery to manage the result. The size issue is stated in advance: rebuilding the wall requires reducing the medial space, so a smaller implant than before often goes in. Keeping a large implant while restoring the central groove pulls in opposite directions — you cannot have both. Deciding this at consultation before starting reduces reopening later for size. Through 3 months after correction, while the central repair sets, a compression band is worn and stomach-sleeping or postures that push the breasts together are avoided.

6. Preventing it at the first surgery

Symmastia is far easier to prevent than to fix. Four things to keep:

Stop the medial border in front of the sternal edge. Digging deeper medially to make a groove removes the wall.
Leave the pectoralis’s sternal attachment. Even using the submuscular plane, release only the lower part and leave the inner upper.
Set the implant diameter within the breast base width. An implant wider than the base pushes medially.
When the chest is tilted, size more conservatively — this covers pectus excavatum and carinatum.

The cleavage groove is set by the original chest width and the seat of the two breasts, so forcing it narrower by surgery leads to this complication. When a request to “bring the cleavage closer” comes up at consultation, the first thing said is how far is safe.

Summary

Symmastia does not resolve on its own. The tissue that held the middle has detached from the sternum so the two pockets communicate, and it is corrected only by surgery that rebuilds the wall.
The most common cause is over-detaching the pectoralis’s sternal attachment in submuscular surgery. All 23 cases were submuscular, and the survey put it at 84.9%.
Correction is layered: re-attaching fascia and muscle to the sternum, changing the plane, reducing size, and post-op compression. Recurrence and size change can happen, so they are decided before surgery.

References

Kalaria SS, Henderson J, Moliver CL. Iatrogenic symmastia: causes and suggested repair technique. Aesthet Surg J. 2019;39(8):863–872. doi:10.1093/asj/sjy307. (23 cases all submuscular; survey of 91, 84.9% submuscular.)
Liu C, Chen Y, Wang Z, Qu Q, Fan Y, Xu Y. Acquired symmastia: classification, causes, and repair strategy. Ann Plast Surg. 2024;92(1):28–33. doi:10.1097/SAP.0000000000003729. (18 cases; 3 recurrences; 4 size-dissatisfied.)
Byun IH, Park SH. Basic strategies of augmentation mammoplasty in patients with tendencies of pectus excavatum and carinatum. Aesthetic Plast Surg. 2023;47(1):54–60. doi:10.1007/s00266-022-03076-2. (132 patients; zero symmastia.)
Zingaretti N, De Biasio F, De Lorenzi F, Massarut S, Parodi PC. An efficient method for the correction of iatrogenic symmastia: a case series. Ann Med Surg (Lond). 2018;29:14–18. doi:10.1016/j.amsu.2018.03.024. (10 cases; no recurrence at 24 months.)
Qiao C, Shi Z, Xu J, et al. Precapsular pocket repositioning: an effective technique for correcting implant malposition in revision breast augmentation. Aesthetic Plast Surg. 2025;49(22):6303–6310. doi:10.1007/s00266-025-04870-4. (29 patients, 52 breasts; mean 7.9 months; no complications.)
Lawrence Z, Stroman JC, Karu H. Novel technique for repair of symmastia using external negative pressure therapy for continuous pre-sternal compression. J Surg Case Rep. 2025;2025(1):rjaf006. doi:10.1093/jscr/rjaf006. (3 cases.)

Medical disclaimer. This article is general information and does not constitute medical diagnosis or treatment advice. Results vary with individual tissue condition and body type; accurate diagnosis and surgical planning are determined through in-person consultation with a board-certified plastic surgeon.

Dr. Kim Uigeon (Board-certified plastic surgeon, Republic of Korea · UNE Plastic Surgery)