Breast implants migrated to armpit area. How can I fix this? Caused by my anatomy or a poor result? 18 month post op

There are a number of reasons why implants can sit too far apart, or migrate towards the armpit.
A helpful salutation to the problem is modification of the pocket where the implant sits. An internal bra can then be used to support your implants more centrally. This will have the added benefit of increased upper pole fullness when your implants are repositioned.

There are a few features of your anatomy that affect the results from breast augmentation. One is that the nipple-areolas are on the lateral half of the breasts, so if the implants were closer together they would point to the outside more than they do now. Another factor is that your rib cage appears to have a lateral slant. These are completely normal but work against having large implants close together.

Thank you for your question. A large portion of my practice is dedicated to breast revision surgery. It appears that your preoperative anatomy reveals that your breasts sit quite low on your chest. When you place an implant with this particular anatomy, the implant sits low relative to the pectoralis major muscle, and therefore exerts more push inferiorly and to the sides. This is fairly predictable and an experienced breast surgeon should be able to evaluate this with you. In your case, I would perform an internal bra-lateral and inferior capsulorrhaphy, however you also would need a lift-mastopexy. Best wishes to you.