Smooth or textured implants for over the muscle BA? How likely is it for smaller implants (300-350cc) to slip out of the pocket?

Hello!  Thank you for your question!  The prepectoral or subfascial approach is certainly a viable one. In terms of the implant type, consideration for a textured implant would be wise as it would significantly reduce the capsular contracture rate vs a smooth a smooth implant in the same position.   Creation of a pocket to fit the implant would minimize rotation and displacement, especially if an anatomically-shaped implant is used. Hope that this helps. Best wishes!

In general I prefer to use a textured implant which seems to
get a grip on the surrounding tissue and is less likely to slip in the pocket.
Additionally going over the muscle prevents problems with a muscle pushing
the implant up or down.

This is a good question for your surgeon. Textured implants have been shown to decrease the risk of capsular contracture when placed above the muscle. However, in my practice I typically use smooth round implants placed below the muscle in a dual plane position. Placing the implant under the muscle provides another layer of camouflage for the implant, and decreases the risk of capsular contracture.