Chin augmentation is the original facial implant procedure and is still the most commonly one performed today. Several different materials of chin implants are available and a wide variety of styles and sizes exist from different manufacturers. Despite the apparent diversity of chin implant options, it is generally viewed as a ‘very simple and safe’ aesthetic facial operation.
But despite this seemingly simplicity, complications from chin implants are not rare. Infection, implant asymmetry/displacement and aesthetic dissatisfaction do occur and are probably more common than plastic surgeons care to know. Part of this is due to the fact that a synthetic material implanted anywhere in the body always has some risk and another reason for complications is also due to surgical technique.
While the chin bone has few vital structures around it, there is the mental nerves to the periphery and the mentalis muscle which drapes directly over the front part of the bone. To clarify the important anatomy that is involved in the placement of chin implants, an article was published in the April 2013 issue of the journal of Plastic and Reconstructive Surgery entitled ‘The Safe Zone for Placement of Chin Implants’. Using fresh cadaver dissections, the location of the exit from the bone of the mental nerves was consistently around 1.5 cms above the lower border of the jaw and located between the first and second premolar (bicuspid) teeth. The origin of the mentalis muscle was at the base of the anterior mandibular sulcus at the incisor roots (the level of the outer labiomental sulcus) and descends downward to insert into the chin soft tissue pad in a fan-shaped manner.
While this article provides no new anatomic information that hasn’t been known for some time, it helps the novice plastic surgeon be aware of the subperiosteal location in which to stay when placing chin implants. (below the muscular origin of the muscle and the mental nerves) Its relevance to the patient is in several issues to ponder when undergoing chin implant augmentation.
While some patients like to avoid a submental scar in placing the implant, one is at greater risk of mentalis muscle problems going from inside the mouth if the muscle is not put back together properly. The submental incisional approach is probably ‘safer’ in many cases and in most surgical hands. In addition, while a 1.5 cm pathway below the mental nerves is fairly generous for the wings of most chin implants, large implants and even custom jawline implants that are bigger are at greater risk of injuring the nerve during dissection and/or have an implant impinge on it afterwards causing lip and chin numbness/pain.
Dr. Barry Eppley
Indianapolis, Indiana