Background: Chin augmentation is the original and the most common area of facial skeletal enhancement. As a projecting edge of bone that is fairly easy to access, placing a chin implant is understandably perceived as a very simple and near error-free facial implant procedure. Despite this commonly-held belief, however, chin implants do have problems and need to be revised, replaced, or even removed.
There are two common chin implant problems, malpositioning and implant selection. Malpositioning of a chin implant can occur in two different ways. Superior or upward migration of the implant usually occurs if it is placed from inside the mouth. While the intraoral approach avoids an external incision, its path of dissection provides an avenue for the implant to slide up along the bone afterwards. Lateral or wing malpositioning is actually the most common problem and is a result of the newer styles having thin and more floppy wing extensions which can easily fold onto themselves. Chin implants can also have size (undersized, oversized) and style (too wide, too narrow) problems which is a preoperative diagnosis and selection issue.
Case Study: This 40 year-old male was unhappy with the result of his chin augmentation. He had two prior chin implant procedures. They were done from an intraoral incisional approach. He felt that his chin was still not defined and prominent enough. He wanted a more masculine chin appearance. He had a record of his indwelling chin implant which was silicone in composition,7mms in projection, with limited lateral wings.
To improve his chin result, two different approaches were discussed for a revisional surgery. First, use a submental skin incision to remove the existing implant and replace a new one at the lowest position on the bone. Secondly, a different implant style would be used that had greater lateral extensions to add more lateral chin fullness and width.
During surgery, the submental incision was done but no implant was found at the inferior border of the chin. Located 14mms above the chin border, an implant was found and removed. There was 2 to 3mms of bone resorption underneath the implant when it was removed. Pockets were dissected out along the lower border of the jaw from the midline about 4.5 cms per side. A new chin implant style, a chin-prejowl design, was then inserted. Pulled down to the lower edge of the bone, the implant was secured with a single 12mm long titanium screw.
The immediate results of this chin implant exchange and repositioning can be seen just one hour after surgery. The chin had more lateral fullness and better horizontal projection, particularly at the low edge of the chin bone which is the most important point of increasing its projection.
Case Highlights:
1) Chin augmentation requires proper placement of the implant on the bone. Intraoral chin augmentation is prone to superior implant migration and malpositioning.
2) Replacement of a highly positioned chin implant is best done from a submental approach with screw fixation.
3) In the male chin augmentation, consideration needs to be given to an implant design that provides more lateral fullness and extends back further towards the body of the mandible.
Dr. Barry Eppley
Indianapolis, Indiana