When you put an implant under the muscle you benefit from three things. First, there is less scar formation around the implant, this is because the muscle continuously messages the implant and breaks up any large scar depositions. In addition, implants tend to tether the overlying skin which is caused by the implant sticking to the skin; The muscle gives a protective layer that prevents tethering of the skin, especially over the upper pole of the breast mound. In addition, going under the muscle gives you a bigger cushion so that you are less likely to feel the implant. But most importantly, by placing the implant under the muscle, you avoid dissection through the breast tissue and subsequently improve the detection of breast cancer.