Background: The projecting chin is a three dimensional structure that has both horizontal projection, vertical height and transverse width to it. But within these bony dimensions on both its outer and inner surfaces are small discrete areas of topographic features. Many of these small bony features are known as fossa and tubercles which means small valleys and hills. These bony surface features of the chin are not there by accident, they are a function of the effects of muscle attachments and pulling effects on the bone.
The definition of a tubercle is a small rounded projection or protuberance on the surface of a bone. This is the direct result of muscle traction on the bone through ligamentous attachments. On the front central surface of the chin is the larger mental protuberance. But off to the sides lies the smaller mental tubercle and the larger platysma tubercle. The larger platysma tubercle runs along the side of the chin. Normally the platymal tubercle is not particularly prominent. But when it is it can create undesired chin width.
Case Study: This female has bothered by her wide chin. She could feel a distinct bulge on each side of her chin. She had a small face but a comparatively broad chin. Because of the prominent tubercles their direct reduction was the best approach. The discussion for its reduction was whether it should be done using an intraoral vs a submental skin approach. The prominent points could be easily palpated and were marked. (she was also going to get fat injections to her chin dimple hence the midline markings)
Under general anesthesia a submental skin incision was used to deglove the soft tissues from the end of the chin bone. A prominent ridge of bone was seen along the sides of the chin along the inferior border. (this is a very uncommon chin bone finding) It actually was like a shelf of bone along the sides. Even though it felt like a single prominence it was more elongated than a single point.
Using a reciprocating saw the shelf-like lateral tubercles were removed, exposing the marrow space of the chin. These were bone weed and the incision closed in layers.
When doing any type of shave reduction to the chin one has to be vigilant about how the soft tissues will adapt to less bone support/volume. There is always the risk of chin pad ptosis as well as chin contour irregularities with movement. The intraoral approach is my experience has the higher incidence of these issues than the submental approach. This is simply due to the difference in going through the bony origin attachment of the mentalis muscle superiorly (intraoral incision) vs the soft tissue insertion of the mentalis muscle inferiorly. (submental incision) The patient has to balance out the tradeoffs of a small skin incision scar vs the soft tissue chin pad contour issues.
Case Highlights:
1) One reason a chin can appear wide is the overdevelopment of their lateral tubercles.
2) Prominent lateral tubercles of the chin can be most effectively reduced by a bone shaving technique.
3) The submental approach for chin width tubercle reduction provides direct access with the least risk of soft tissue chin pad contour irregularities.
Dr. Barry Eppley
Indianapolis, Indiana