Background: The sliding genioplasty is a conceptually straightforward procedure. Cut the bone, move it forward and fix it into the desired new position.. It sounds simple enough but there are a lot of variables in its execution that can lead to an unsatisfactory outcome. The first important step is to determine the patient’s exact aesthetic goals. It doesn’t matter how well you do an aesthetic operation if the specific changes made are not in line with that of what the patient desires.
While the sliding genioplasty is historically aligned with orthographic surgery, and is still often performed as part of jaw repositioning surgery, the determination of the bone movements has little to do with cephalometric points and meaurements. That conceptual approach should be completely ignored. Preoperative imaging of different chin changes using the patient’s pictures, usually in side profile if horizontal augmentation is the primary chin augmentation change. The key element in this imaging is different changes made in reference to a vertical line dropped down from the lower lip. (behind it, at it and past it)
Once the patient’s flavor of change is established the number of millimeters needed to make that change is determined by caliper measurements in the amount of soft tissue pogonion movement to a vertical line (tongue blade) dropped down from the lower lip. This number is then used to determine how much change the patient wants based on their imaging selection. The fixation plates used to set the new position of the chin come in 2mm increments from 2 to 16mms. With 2mm differences in plating options this should allow enough variability to come reasonably close to the patient’s preoperative determined goals.
Case Study: This male desired a strong chin augmentation effect in a pure horizontal movement. He chose the chin advancement that when beyond the lower lip line. With a pogonion to lip measurement of 8mms that meant a 10mm advancement should be adequate to meet his goals.
Under general anesthesia and through a 3cm intraoral vestibular mucosal incision a low oblique horizontal osteotomy was performed with a 10mm plate advancement applied. Due to the large bony step off it was grafted with 5cc of cadaveric bone chips.
The small intraoral incision was closed with resorbable sutures.The length of the incision stays between the canines.
The immediate change in chin projection could be seen intraoperatively although the projection looks less than the preoperative determined as the patient can not fully close his mouth. (due to the endotracheal tube)
Preoperative imaging to determine a patient’s aesthetic goals may not be an exact science but it is a far better approach than using standard cephalometric measurements or just doing what the surgeon thinks look good.
Key Points
1) The sliding genioplasty is a common chin augmentation procedure but determining its dimensional changes require a precise preoperative method for doing so.
2) The flavor of the patient’s desired chin change is determined in reference to a vertical line dropped down from the lower lip.
3) The risks of postoperative lower lip tightness and deepening of the labiomental fold can be reduced by immediate grafting of the bony step off.
Dr. Barry Eppley
World-Renowned Plastic Surgeon