Background: Chin implants are the most common form of aesthetic facial augmentation of which a wide variety of styles and sizes exist. Such a large selection of chin implant options would lead one to believe that almost any type of chin reshaping option is possible. But the reality is that the available chin implant options work well under three specific circumstances, 1) the amount of augmentation is not excessive in size (under 10mm), 2) the desired direction of augmentation is horizontal and 3) the desired chin shape is round or somewhat square.
Many surgeons when faced with an atypical chin implant shape request naturally look at standard implants to try and make them work. While there is merit in that approach there are limitations as to how effective that can be. These limits are largely based on the surgeon’s experience with modifying by hand existing chin implants and their experience with screw fixation of them. Trying to take a standard implant shape and put it in an unstable position on the bone are circumstances that have a high rate of aesthetic failure/asymmetries.
One unique circumstance for a chin implant is a secondary augmentation after a prior sliding genioplasty. When improving the shape of the chin after a sliding genioplasty consideration must be given to correction of the bony defects along the back end of the prior osteotomy. This combined with a specific shape request may make it an unobtainable result with a standard chin implant.
Case Study: This female had prior chin surgeries that consisted of a sliding genieplasty followed by the placement of a large anatomic chin implant. Her goal was to have more narrow and tapered chin shape. Instead she got a round and asymmetric chin shape. A 3D CT scan showed a malpositioned chin implant hanging off of the bone that elongated her chin and was shifted to one side.
Using a 3D CT scan a custom chin implant design was done using the positive information from the existing chin implant. (amount of horizontal projection) as well as its negative effects. (vertical elongation, round shape, asymmetry, inadequate posterior jawline coverage)
Comparing the indwelling implant vs the custom design shows the significant differences in the shape and effect. The v-shape may look extreme but to overcome the thick soft tissue chin pad an implant’s design must often need to be exaggerated.
Through her existing submental incision the old chin implant was removed. Comparing the two implant shapes side by side was as significant as seeing it on the design file.
The custom implant was placed with positioning assured by the superior extension of the implant between the inferior legs of the existing genioplasty plate. A single self-tapping screw was used for fixation.
The differences in the chin shape from round to more tapered was immediately apparent.
1) Trying to make s standard chin implant do what it is not designed to do often leads to undesired effects.
2) A vertically inclined chin augmentation that creates a more v-shaped chin can only be effectively accomplished by a custom chin implant design.
3) Most custom chin implants are best secured by at least one point screw fixation.
Dr. Barry Eppley