Several of the most important reasons to go behind the muscle are to add tissue to mask rippling and to blend the edges of the implants so that they are less conspicuous.Since teardrop implants (specifically the Allergan 410) rarely ripple, and since their tapered edges blend well into the natural breast surrounding the implant, it seemed logical to conclude that they would do well in front of the muscle.The implant was first used in Sweden in 1993 and most of the first cases were in front of the muscle. Rippling was not an issue. Early results were great. But after a year or two they were noticing that the tissue over the implant was thinning from the pressure of the implant and that the edges were gradually becoming more obvious.For that reason they soon switched to behind the muscle and that is the standard way that it has been taught since US clinical trials began in 2001. I've done thousands of these over these past 15 years and with few exceptions have placed them behind the muscle.The purported disadvantages of going behind the muscle are illusory: there is not any more pain, cleavage can be created, and any amount of fullness in the upper breast is possible. The only notable trade-off is that when you contract your pectorals muscles you will see some movement of the implant and even some traction on the skin in the lower inner breast in thin patients. You need to be aware of this, but it is well worth the tradeoff in most situations.More specifically the current way to place implants behind the muscle is "dual-plane." That means the surgeon decides exactly where and how much muscle coverage will best suit a particular patient and precisely performs the surgery to control the muscle in that position. "Half over/half under" are commonly used misnomers and have no basis in anatomy.