Background: Symmetry of the lower third of the face, and the jawline specifically, is one of the most important components of facial aesthetics. Asymmetry in the jawline can occur in any of its components from the chin, body or ramus of the mandible. Differences in lengths of the ramus due to development is one of the major causes of jaw asymmetry. Since much of jaw growth comes from the condyle, it is not surprising that the adjoining ramus would be most commonly affected.
There are a variety of well known and classic jaw developmental abnormalities. Hemifacial microsoma is when one side of the jaw fails to develop properly and the face deviates towards the shorter side. Hemifacial hypertrophy, which is far more rare, occurs when one side of the jaw develops an overgrowth. The face is still very asymmetric but the face twists less and one side of the face looks more full although not necessarily deviated like that of hemifacial microsomia.
In extremely rare cases, both sides of the jaw are affected asymmetrically. One side of the jaw is demonstrably shorter while the other side is clearly longer. The exact cause of this type of growth disturbance is unclear although it is likely more of a lower jaw hypertrophy compared to a perhaps normal but naturally shorter opposite side.
Case Study: This 20 year old female presented with facial asymmetry that was related to her lower jaw. A panorex and 3D CT scan showed vertical elongation of the right side of her jaw that pulled the inferior alveolar nerve down with it. There was a full 1 cm elongation based on the location of the mental nerve foramens. Computer imaging was done to determine if just one side of the jaw needed to be shortened, the other side just needed to be lengthened or whether a combination of both changes was needed. It was determined that her jaw asymmetry correction would be best done by a right inferior border osteotomy shortening and a vertical elongation of the left side. A custom vertical lengthening jawline implant was made from a 3D CT scan for the left side.
Under general anesthesia and through intraoral incisions, an reciprocating saw was used to reduce 5 to 7mms off the lower end of the chin and jawline back to the angle. On the left side the custom jawline implant was inserted and stabilized by multiple small titanium screws.
Her 6 month results showed a much improved symmetry of the lower face. The inferior edges of the jawline were nearly comparable. There was still a slight asymmetry with the right side being slightly longer although it could not be further shortened without risk of injury to the intraosseous nerve location.
Jaw asymmetry correction requires a 3D scan and computer imaging to determine the optimal surgical methods for both sides. When the procedure should be done through an exclusive intraoral approach.
Highlights:
1) Jawline asymmetry can be caused by a vertical shortening or lengthening of one side of the jawline or a combination of both.
2) In bilateral jawline asymmetry lengthening of the shorter side and shortening of the longer side is needed for jaw asymmetry correction.
3) Jawline lengthening is best done with a custom made implant. Shortening of the longer side must take into account the location of the inferior alveolar nerve.
Dr. Barry Eppley
Indianapolis, Indiana