Good bone structure is a major determinant of human beauty. Individuals with oversized noses often seek surgery to restore harmony among skeletal features and improve facial beauty. After nasal surgery, perhaps the next most commonly performed surgical modification of the facial skeleton is chin augmentation. In fact, large noses and small chins tend to occur in pairs making chin enlargement a frequent tandem surgery with cosmetic rhinoplasty. Because an oversized nose makes a small chin appear smaller (and vice versa), correcting both features simultaneously has a dramatic and synergistic impact upon the cosmetic result.
Chin augmentation can be performed in a variety of ways, depending upon the underlying cause of the deficiency.
For patients with severe developmental bite relationships between the upper and lower jaws, known as malocclusion, a simple chin enlargement will not address dental misalignment issues or potential complications with premature wearing of the teeth and/or temperomandibular joint dysfunction (TMJ). In this case, orthognathic surgery is required to surgically reposition the upper and/or lower jaw bones to restore proper occlusion and bite relationships. Fortunately, these problems are rare and the complexities and risks of orthognathic surgery is seldom required.
For the remaining individuals with a small chin and normal bite relationships, less invasive but equally effective alternatives are available. In these patients, the teeth are straight (often as a result of orthodontics), but the chin bone, also called the mental process or the mentum, is too small, a condition known as microgenia. Patients with microgenia can have chins that are horizontally deficient, vertically deficient, or both. Fortunately, microgenia is not associated with functional abnormalities and represents only a cosmetic concern.
The cosmetic treatment of microgenia involves lengthening the chin, extending the chin forward, or both, depending upon the specific type of microgenia. Although pure horizontal microgenia is the most common, ranging in severity from mild to moderate, severe cases of microgenia usually involve both horizontal and vertical deficiencies. In contrast, severe vertical microgenia is seldom seen in isolation.
While some surgeons prefer to physically lengthen the jaw itself, an operation known as a sliding genioplasty, in my opinion this procedure is unnecessarily invasive and risky. Sliding genioplasty involves sawing off the mental process while avoiding injury to the sensory nerves and tooth roots, then advancing the chin bone forward and securing it in a cosmetically pleasing alignment using plates and screws. In addition to the risk of lip numbness and devitalized teeth, there is also a risk of bone resorption from a disrupted blood supply and/or infection of the plating hardware, particularly since the procedure is performed through a large intra-oral incision with contamination from saliva. Finally, the cosmetic impact of sliding genioplasty is often disappointing unless spacers or plates are used to fill the gap between the jaw and the chin fragment. Although it is often touted as an alternative to synthetic implants, sliding genioplasty is nearly always performed using synthetic or artificial materials.
Augmentation Genioplasty with Synthetic Implants
A popular alternative to sliding genioplasty is augmentation genioplasty, which uses a synthetic chin implant to augment bone contour. Chin implants have been used successfully since the 1960's and are now the most common treatment for microgenia. Early implants fashioned from solid silicone are now giving way to modern porous implant materials with improved safety and performance profiles. Materials such as porous polyethylene (Medpor®), an inert plastic polymer, are engineered to be tissue-friendly with a very low risk of tissue rejection. Available in a wide variety of pre-formed shapes and sizes to accommodate virtually any specific type of microgenia, all Medpor® implants are all manufactured with microporous channels to permit rapid and complete vascular ingrowth. Vascular ingrowth is a major advantage over non-porous implants such as silicone for two reasons. First, penetration of the entire implant by vascularized soft tissue promotes adherence of the implant to the underlying bone. Unlike non-porous implants such as silicone that encapsulate (or form a fibrous sac or capsule around the implant) and move freely with the soft tissues, porous implants adhere to the bone and feel like real bone — both to the patient and to anyone who touches the jaw. The lack of mobility also prevents erosion of the underlying bone, a problem commonly seen in mobile implants. More importantly, vascular ingrowth also permits complete access of the implant to the immune system, thereby greatly reducing the long-term risk of implant infection. However, vascular ingrowth does not preclude safe removal of the implant should that become necessary.
Like all synthetic implant materials, porous chin implants should be exposed to a little contamination as possible. Although inserting the implant through the mouth conceals the incision, intra-oral insertion also bathes the implant in contaminated saliva. Because a small skin incision beneath the chin is unlikely to result in a visible scar, extra-oral insertion is recommended for chin implant placement. In addition to reduced contamination of the implant, extra-oral insertion also results in far less tissue disruption with a corresponding reduction in risk, pain, swelling, and recovery time. Typically, with the extra-oral approach, patients are chewing and speaking normally by the following day. Because chins are seldom perfectly symmetric, synthetic implants can also be modified in surgery to compensate for asymmetries. Medpor® implants are firm yet malleable, and can be carved with a scalpel for a more precise custom fit. For all of these reasons, I use Medpor® implants exclusively.*
* I have no financial interests in Porex (manufacturer of Medpor® facial implants), and I am not a paid consultant for Porex. I received no compensation, monetary or otherwise, for the above unsolicited endorsement.