Deep Transdermal Placement
In theory a transdermal implant should be placed essentially no deeper than a piercing. If it is placed deeper, not only will it be far more difficult to remove, but secondary complications can easily occur such as an inward traveling infection.
Because transdermal implants are typically placed using a dermal punch to create the main point of exit for the jewelry, initial damage can be easily done to the muscle and periosteum, or even scratch the skull itself, creating weak points for future infections. In addition, the jewelry itself can erode tissue below it until the transdermal settles on the bone itself and can begin to cause life-threatening complications.
Please understand that the above diagram is not to scale and overly simplified.