Background: Correction of chin deformities is based on what dimensions of it need to be changed. The most common chin deficiency is horizontal for which either an implant or a sliding genioplasty is used to treat it. It may or may not be accompanied with a vertical deficiency as well.
One of the least common chin deformities is vertical excess also known as vertical macrogenia.. This is typically seen when the mandibular symphysis has grown too much in the vertical dimension. The chin looks too long and the lower third of the face is out of proportion to the upper two-thirds of the face. It is also seen in the long face where every facial third is increased.
A unique type of vertical macrogenia is when a chin implant is placed too low on its anterior edge. This can occur from either an inadvertent tilt to the implant or that the whole chin implant is too low, hanging off the edge of the inferior border of the chin. When the chin implant has overhang it will create an implant-induced vertical macrogenia. This is obviously correctable by adjustment of the implant back up into the proper position. But of the implant material allows for substantial surrounding tissue adhesion moving the implant may not be as simple as that of a silicone chin implant.
Case Study: This male had a history of a Medpor chin implant being placed through an intraoral incision. While he liked the additional chin projection and width, he felt it made his chin look too long. On examination it could be seen that there was an abnormal ridge below the chin which as well below the anterior projection of the soft tissue chin pad. The cleft of the implant where it is united after being put in as a two-piece unit could be felt and the implant hung below the bone by about 5mms with a very palpable step-off.
Under general anesthesia and through a submental incision, the Medpor chin implant was exposed and the cleft between the two implant pieces seen. The cleft through the implant was taken advantage of and a scalpel used to cut off one side of the implant at the 5mm amount in the horizontal direction.
The other side of the implant was then removed, leaving a sharp anterior edge which was smoothed off with a high speed handpick and burr. This left him with a vertically shorter and slightly more square chin as well as elimination of the submental bulge or ridge below the chin.
The tissue adhesion of the surrounding soft tissue of a Medpor chin implant makes it easier and less traumatic to modify its shape in situ. (without removing it) This would normally be very difficult with the exception of its vertical dimension which can be directly accessed and visually seen through a submental incision. Shaving off the overhang back up to the level of the inferior order provides an effective treatment for implant-induced vertical macrogenia.
1) A long chin (vertical macrogenia) can be surgically induced by the malposition of a chin implant.
2) Implant-Induced vertical macrogenia can be effectively treated by removal of the chin implant overhang.
3) A submental approach provides the most direct and accurate approach to modify/adjust the implant.
Dr. Barry Eppley