Sientra implants come in both smooth and textured, and if your surgeon had used textured implants, that would be the main reason they would not drop over time. If placement is asymmetric, then they stay that way (assuming tissue adherence). But you had 380cc smooth cohesive silicone implants, and did not specify if they were subglandular (below the breasts) or submammary (below the muscles). The most likely reason you still have somewhat high implant position, as well as residual asymmetry, is that you had pre-operative asymmetry that identical implants can make more visible, and different rates of implant dropping.Another possibility that only breast examination can reveal is early capsular contracture (CC). CC can occur with subglandular AND submuscular implant placement, but the likelihood of early capsular contracture is more likely with above-the-muscle implant placement. However, regardless of position, unilateral or bilateral CC could also be a possible cause of your present appearance.Elastic bandeaus worn above the "high" implant breast and below the "lower" implant breast will help to reduce any residual asymmetry by helping to stretch the still-immature scar in the breast pocket, allowing the implant on the "high" side to continue to soften, settle, and drop. The band's position below the already-dropped implant will help to slow any further drop as healing progresses for its full 6-12 months.Prevention during surgery? Possibly, but we all strive to do the exact operation needed on each breast, which almost always starts out different from the opposite side. Plus, there may be more bruising, swelling, scar tissue, arm use on the dominant side, sleeping more on one side than the other, increasing swelling in the "down" breast, etc. on one side than the other. What happened to you is very common, and very much improvable by appropriate aids during the healing process. Talk to your surgeon, who appears to have done a nice job. Best wishes! Dr. Tholen