While much thought goes into the horizontal projection of the chin, and numerous chin augmentation procedures exist to change it, much less interest is in its other dimensions. One often overlooked deficiency of the chin is its vertical length. A short vertical chin is usually associated with a flatter mandibular plane angle where the horizontal position of the chin and jaw angle points are almost on the same line.
While some vertical chin deficiencies are part of an overall underdeveloped chin (both vertical and horizontal shortness) some chins may have an isolated vertical deficiency. The chin may have enough forward projection but just looks short. This is usually very apparent when the classic vertical thirds of the face are considered.
Vertical lengthening of the chin as an isolated change can be done by an opening wedge bony genioplasty. Just like the osteotomy used in the classic sliding genioplasty the same intraoral bone cut is made. But instead of moving the bone forward, the front edge of the bone is dropped downward. With the back wings of the inferior bone segment staying in contact with the bony jawline, the front part of the chin is vertically lengthened by the size of the opening wedge. (bony gap) This gap and the vertical chin lengthening it creates is maintained by plate and screw fixation.
This opening wedge of the chin creates a bony gap. If this bone defect is not too big, bone will naturally fill it in over a period of up to six months after surgery. The exact size of a horizontal bone gap in the chin that can heal on its own is not precisely known. But the general rule that I use is that I don’t graft this gap when it is less than 5 or 6mms. But when the gap is closer to 8 to 10mm it is of benefit to do so.
Interpositional grafting of an opening wedge genioplasty can be one by a variety of materials. The use of allogeneic or cadaveric blocks or granules is an effective. A large solid block placed in the center grafts the biggest part of the defect and the sides can be left alone to heal in on their own.
Vertical chin lengthening helps to put the face in better balance and fixes an uncommon chin deficiency that is best appreciated in the frontal view.
Dr. Barry Eppley
Indianapolis, Indiana