The sliding genioplasty is a well known chin augmentation procedure that is commonly used for horionzontal advancement. But cutting and moving the chin bone can be done for other dimensional changes of which vertical lengthening is also a good indication. Historically vertical lengthening of the chin could only be done with an opening bony genioplasty.
When the chin bone is fractured and moved downward it is held into its new position by a plate and screws. Such fixation devices can increase the vertical length of the chin up to 1 cm or more. This leaves a large bone gap between the two cut bone edges. The question has always been at what amount of opening should the gap be filled and with what material?
There is no exact science that tells us what size bone gap in a vertical lengthening genioplasty can heal in on its own and what size bone gap can not. The chin does have a remarkable capacity to create bone from its two cut bone edges. As a general rule I do not place any interpositional material for bone gaps less than 6mms. But larger amounts of vertical chin expansion merit some graft material to aid bone healing
While a bone graft would be the ideal material to place into a vertical lengthening genioplasty, harvesting a bone graft for an elective aesthetic procedure is not appealing. A wide variety of alloplastic materials have been used instead of which hydroxyapatite granules and blocks are the most common.
An other graft option is that of tissue bank or cadaveric bone. Available from a variety of tissue banks in the U.S., processed solid wedges of corticocancellous bone are available for human implantation. These are excellent interpositional graft choices for a vertical lengthening genioplasty. Placed behind the fixation plate in the central opening of the bone, they not only add to structural stability but provide a scaffold for bone ingrowth. The entire opening wedge of the genioplasty does not need to be grafted, only the largest gap in the center. The wedge shape of the corticocancellous bone makes it an ideal fit for this type of bony opening.
The options for filling the bone gap of a vertical lengthening genioplasty are either hydroxyapatite blocks or tissue back bone. Both can be very effective and their cost differences are not significant.
Dr. Barry Eppley