Animation (or "dynamic") deformity is temporary movement or distortion of the breast when the pectoral muscle contracts — for example during exercise. It occurs when implants sit under the muscle.
Why it happens
With sub-muscular and, to a lesser extent, dual-plane placement, flexing the chest muscle squeezes and shifts the implant, momentarily flattening, dimpling or moving the breast. It settles when the muscle relaxes.
Who it affects
It is most noticeable in very active or muscular people. Severity varies, and many patients are not bothered by it.
Reducing it
Options include over-the-muscle or subfascial placement, which avoid the muscle entirely. Significant, bothersome animation can sometimes be improved by converting to a different plane at revision.