This is a great question as there is a common misconception that only saline implants can be used for trans-axillary breast augmentations. The vast majority of the time I use silicone implants for my axillary breast augmentations.
I have placed implants as large as 700cc in through the axilla with the use of the Keller funnel. The funnel allows the implant to go in though the axilla easily and smoothly. Patients should not limit what implant they would like to use because of the incision that they want for their breast augmentation.
Many patients that chose to have a axillary breast augmentation want it because it will conceal their scars and give them a very natural appearance. The use of silicone implants aids in giving patients the most natural appearance possible.
If you are interested in an axillary breast augmentation with silicone implants please see a board certified plastic surgeon with experience in the procedure as they will be able to help guide you!