Chin reduction can be done in a variety of dimensions. What those dimensions are determines whether an intraoral or extra oral (submental) technique is used. Besides the bone dimensions consideration must also be given to how the enveloping soft tissues will respond to the reduction in bony support.
One of the most interesting dimensions in chin reduction is the vertical one. In pure isolated vertical chin reduction it can be done by an intraoral wedge of bone removal. (osteotomy and plate/screw fixation) Soft tissue redundancy is not usually an issue as it remains attached on the inferior edge of the bone and is pulled up along with the reattached bone segment…so there is no risk of soft tissue sag. However in the patient who has had previous chin surgery, such as implants and/or a bony genioplasty, this may not be a viable option.
When a submental vertical chin reduction approach is needed it does offer the ability to control all three bony dimensions as well as any soft tissue excess as well. Coming from below a caliper can be used to precisely remove the desired amount of bone at the midline.(obviously tapers in the bone removal as it goes to the sides) Through the small skin incision the bone cut can be safely done with a reciprocating saw by carefully doing half at a time and changing saw position from one side of the chin to the other.
Once the bone cut is complete all the way through the bone it will easily downfracture…but will not so easily come out of the incisional opening. This is because of the attachment of some fibers of the geniohyoid muscle. These robust muscle fibers must be released and then the bone is free to be removed. The remaining superior bone will have some sharp edges which will eventually need to be smoothed.
But before doing so the sides of the chin bone need to be shaved as the chin becomes shorter it will also become wider. A good lateral reduction or narrowing requires good exposure and seeing the mental nerve is the surest way to know that it is out of harm’s way. A reciprocating saw is the best way to make a smooth and aggressive side cut which is what is aways needed. At a 45 degree angle the sides of the chin bone are cut and removed.
Once the bone reduction/shaping is done the overlying soft tissue must be readapted to it. This involves resuspending the geniohyoid muscle to the bone as well as removing any soft tissue redundancy.
Dr. Barry Eppley