Jaw angle implants are to the back of the jaw like chin implants are to the front. They have become more popular for facial augmentation as the aesthetic value of the back of the jaw, or the entire jawline, has become recognized as creating a such enhanced lower third of the face. No longer should jaw augmentation be perceived, by patient or the surgeon, as a chin augmentation procedure only.
While the similarity between a chin implant and jaw angle implant is that they augment the same facial bone, that is where their association largely ends. Jaw angle implants are placed exclusively from intraoral incisions, a chin implant can be placed either from an intraoral or extraoral approach. A chin implant involves a single midline device placement, jaw angle implants require the placement of two devices with the goal of symmetry in their bony position. A chin implant is placed under the mentalist muscle which has a role in lower lip movement, a jaw angle implant is placed under the masseter muscle which plays a major role in jaw opening and closing.
On closer inspection of their submuscular placement on the bone, some critical differences exist in that regard between chin and jaw angle implants. No matter how a chin implant is placed, it requires cutting through the mentalist muscle and then putting that muscle back together at closure. For a jaw angle implant it is of critical importance to preserve the muscle integrity at the pterygomassteric sling. The goal is to not cut the muscle or inadvertently separate the pterygomasseteric sling, a technical maneuver that sounds easy but it is not. Failing to do so can result in loss of masseter muscle coverage over the bottom part of the implant.
In cadaveric dissections it can be seen how thin the inferior border attachment is between the outer masseter muscle and the inner pterygoid muscle. While in widening jaw angle implants it is not necessary to elevate along the inferior border, this is a necessity in vertical jaw angle implants. Gentle inferior border elevation to preserve the lower end of the masseter muscle attachment can be successfully done. An appreciation of how thin that attachment is helpful in at that point in the pocket dissection for jaw angle implants.
Dr. Barry Eppley