Chin reduction can be done by a variety of surgical techniques which fundamentally separate into two basic approaches. The superior intraoral approach offers either an outer cortical burring technique (2D) or an inverted t-shaped osteotomy (3D) for chin size reduction. The inferior submental approach provides access to do bone shaving/removal in all three dimensions of width, height and projection. And it also offers the ability to do some limited soft tissue reduction as well.
Once of the main advantages of the submental chin reduction method is the ability to perform significant vertical bone shortening. A straight osteotomy cut across the bottom of the chin can be done with typical removals of 5 to 7mms. The bone comes out in the shape of a horseshoe which is the inferior cortical bone.
In removing the inferior portion of the chin bone it is necessary to detach a portion of the genioglossus muscle. This is a fan-shaped that has its origin on the back side of the chin bone (mental spinous process) and moves posteriorly to become part of the tongue superiorly and attaches to the hyoid bone inferiorly. Because if it being the only anterior attachment of the tongue it has been called the safety muscle of the tongue. Its relevance to the upper airway is seen in the genioglossus advancement procedure that is one of the procedures to treat obstructive sleep apnea.
While the entire insertion of the genioglossus muscle is not detached in a vertical chin reduction it is still a good idea to resuspend the muscle fibers put up in place. This is most easily done by placing transosseous holes through the outer cortex of the front edge of the chin. The released muscle fibers are then sutured up to the bone as the resuspension point.
The main reason to resuspend whatever genioglossus muscle has been released from the back side of the removed bone segment is aesthetic. Not stretching the muscle back out will create a submental fullness under the vertically reduced chin through potential hyoid contraction and submental soft tissue thickness.
Dr. Barry Eppley