Background: The sliding genioplasty is a well known chin augmentation technique for horizontal advancement of a short chin. It is used most commonly for the horizontally deficient bony chin. With these forward movements some vertical change can also be affected, either opening it slightly or even vertically shortening it.
A lesser known use of the bony genioplasty is to vertically lengthen the chin. This its actually the simplest movement of the inferior chin segment as it is opened up and elongated using the posterior bony wings as a cantilever. The amount of elongation is based on the vertical width of the bony gap created between the upper and lower segments. The gap is stabilized by a spanning titanium plate with two screws above and below for form fixation. When the bony gap gets to 8mm to 10mms an interpositional bone graft is used to ensure bony healing.
How much one needs to aesthetically lengthen the chin can be determined by preoperatively opening the jaw, find the best chin lengthening effect and then measuring the distance between the upper and lower teeth edges. (minus any upper incised overbite) If the vertical distance exceeds 10mm to 12mms, one will ned to consider a two-stage vertical chin lengthening approach.
Case Study: This young male wanted to vertically lengthen his chin. It was determined that 10mm was a good and maximal distance. The horizontal osteotomy was made and the 10mm opening wedge gap stabilized with an 8mm chin step plate that was flattened out. A cadaveric block bone interpositional bone graft was placed in the gap.
Six months later a panorex x-ray shows complete bony consolidation across the graft site as well as at the end of the original osteotomy bone cuts. The bony spaces between the bone graft and the ends remained incompletely filled.
He wanted an additional 10mms of vertical chin lengthening so a second bony genioplasty was performed. The metal plate and screws were easily removed (non-bony overgrowth) and the chin bone was solid. A horizontal bone cut was made across the original osteotomy line and the chin easily downfractured. It was dropped down another 10mms, fixed with a flattened out 12mm step chin plate and secured with screws. Another interpositional bone graft was placed on both sides of the bony gap.
Interestingly at 20mms of vertical chin lengthening, no lower lip incompetence of strains occurred. Presumably this was because it was a staged bony lengthening approach.
Highlights:
- Vertical lengthening genioplasty lengthens the lower third of the face by an opening wedge osteotomy.
- When the vertical lengthening of the chin is at 8 to 10mms a cadaveric interpositional bone graft is needed for bony healing
- A second vertical lengthening genioplasty can be successfully done after the first one with a final lower third of the face increase of 20mms.
Dr. Barry Eppley
Indianapolis, Indiana