Background: Facial asymmetry is not uncommon and can occur from multiple causes. One of the most common is that from plagiocephaly where the entire craniofacial skeleton rotates or twists around a central axis resulting in a classic pattern of skull and facial bone asymmetries. But most facial asymmetries do not have such well identified causes and are usually idiopathic….it is just the way the face developed.
Jaw or mandibular asymmetries are one of the most common and identifiable anatomic causes of facial asymmetry. The size of the lower jaw and the importance of the chin and jaw angles on facial appearance can make even small jaw asymmetries very noticeable. Jaw asymmetries come in a wide variety of types but most commonly it presents when one side of the jaw has either overgrown or one side has under developed. This results in a twisting of mandible such that the chin is deviated either towards the smaller side or away from the overgrown side.
Many jaw asymmetries are associated with a malocclusion (bite that is off) which is best treated by a combined orthodontic and jaw surgery combination. But when the bite is acceptable or the patient does not want to undergo orthognathic surgery, aesthetic correction of the jaw asymmetry can still be done.
Case Study: This 22 year old male has lower facial asymmetry with a smaller right side, a chin deviation to the right and a more pronounced left jaw side/angle. A 3D CT scan shows that the right mandible was shorter and the left mandible was longer. This created the chin deviation to the right of the facial midline.
Under general anesthesia he had a left jaw angle reduction, a right jaw angle implant placed (width only jaw angle implant) and a leveling chin osteotomy. All jaw procedures were done from an intraoral approach. Reduction of the left jaw angle accounted for a 5mm narrowing of the jaw angle flare. A 7mm wide lateral jaw angle implant was placed on the right. The intraoral chin osteotomy consisted of an asymmetric wedge removal and shifting of the chin bone back towards the midline.
His jaw asymmetry correction surgery showed a good improvement. In an ideal world I wish just reducing the larger jaw on the left side of his face would straighten it but that almost never can happen by itself. The reason is that you can not reduce the larger bone enough to make a big difference. (there are teeth and nerves in the bone so that is a limiting factor as to how much bone can be reduced) For these reasons this is why most jaw asymmetry corrections must employ a ‘three point’ approach. This means all three points of the jaw (chin and two jaw angles) are treated. Reducing the left jawline, straightening the chin and augmenting the right jaw angle in this case provides the most comprehensive approach to jaw asymmetry correction. Even with this approach perfect lower facial symmetry is not usually possible. But it is usually the best approach to mask the lower facial disproportion which now exists.
Highlights:
1) Jaw and lower facial asymmetry is a developmental deformity that usually affects the entire jawbone from angle to angle.
2) It is rare that just treatment of one side of the jaw asymmetry will result in a very good correction.
3) Jaw asymmetry correction is best done by treating the three points along the jawline, the chin and both jaw angles.
Dr. Barry Eppley
Indianapolis, Indiana