Breast implants often shift outward when lying down, a phenomenon known as lateral displacement. While standing, gravity pulls the implants downward and keeps them centered, but this force changes when you lie on your back. This article explains the mechanical and anatomical reasons for this movement and helps distinguish between normal animation and signs that may require medical attention.
Understanding Why Implants Move
Breast implants are placed within a surgical pocket, which forms a scar tissue capsule around the device. When transitioning from standing to lying down, the gravitational vector shifts. The implant is no longer pulled toward the feet but toward the back and sides of the chest. This change in force allows the implant to slide laterally along the curved rib cage, moving toward the armpit area.
The degree of movement is heavily influenced by the implant’s placement relative to the pectoral muscle. Subglandular placement, above the muscle, typically results in movement that mimics natural breast tissue, flowing laterally when supine. Submuscular placement, beneath the pectoral muscle, restricts downward movement when standing but allows for significant lateral shifting when the muscle relaxes. If the implant pocket is too wide or stretches over time, it provides excess room for the implant to migrate sideways.
When Lateral Movement Is Expected
Lateral movement is a natural consequence of having a device inside a flexible tissue pocket. This shifting is usually a cosmetic preference issue rather than a medical problem. Movement is considered normal implant animation if it stops at the natural outer boundary of the breast or the edge of the chest wall.
Normal lateral displacement should be symmetrical and consistent across both breasts. This movement reflects how gravity acts on the implant and surrounding soft tissues when the body is horizontal. Smooth-shelled implants are designed to move freely within the capsule, which contributes to a natural look when upright but allows for greater movement when lying down.
Identifying Signs of Complication
Excessive lateral movement, resulting in the implant migrating significantly toward the armpit or causing a noticeable gap in the center of the chest when lying down, may indicate implant malposition. This often occurs if the surgical pocket was initially dissected too wide laterally. Over time, the weight of larger implants can also stretch the lateral tissues, enlarging the pocket and allowing for progressive displacement.
Another complication is capsular contracture, where the scar tissue capsule around the implant tightens excessively. While contracture usually restricts movement, a lax capsule that is too large can also cause excessive lateral sliding. A medical evaluation is warranted if the lateral shift is accompanied by pain, noticeable firming of the breast, or significant distortion visible even when standing.
Correcting Excessive Lateral Displacement
If lateral shifting is excessive or due to a complication, surgical revision is required. The common procedure to correct this is a capsulorrhaphy, which involves surgically tightening the stretched scar tissue capsule on the lateral side with internal sutures. This technique reduces the size of the implant pocket, preventing the device from migrating too far outward.
When tissue quality is poor or the capsule is thin, supportive materials may be incorporated to reinforce the repair. These materials, such as Acellular Dermal Matrix (ADM) or surgical mesh, provide extra strength to the newly tightened lateral wall. Surgeons may also consider switching to a more form-stable or textured implant, which adheres better to the surrounding capsule and resists lateral movement.