Chin Alloplastic Implants Treatment & Management

No appropriate medical therapy is available.

The surgical treatment of microgenia includes procedures beyond the purview of this article and can be found elsewhere in Medscape Drugs & Diseases (see Orthognathic Surgery). These techniques include orthognathic advancements of the mandible and/or chin, including the simplest technique, sliding genioplasty; nonalloplastic and/or autogenous implantation; and alloplastic chin implantation. The last of these, discussed in this article, corrects microgenia with the use and insertion of alloplastic implant materials.

Conceptually, a space is created over the surface of chin (mentum), and an implant is placed in this space. The list of types of alloplastic materials available and those that have been used is quite extensive and includes silicone, Proplast, Teflon, Dacron, Gore-Tex, Mersilene mesh, acrylic, porous polyethylene (Medpor), Proplast I and II, methylmethacrylate, and hydroxyapatite. ^[9] The most commonly used alloplastic implant material is silicone. Technically, the procedure for implantation is basically the same regardless of implant material type.

The preoperative regimen varies with physician preference. The author reviews the surgical plan with the patient during the week prior to the scheduled surgical date. At this time, the course of surgery, postoperative instructions, and surgical risks are discussed. The patient has the opportunity to have questions answered, and the surgical consent is signed.

For 2 weeks before and after surgery, patients are asked to eliminate all medications, vitamins, and food supplements that have not been authorized specifically by the surgeon and/or his or her staff. Alcohol, aspirin, aspirin-containing medications, nonsteroidal anti-inflammatory drugs (NSAIDs), and the complete list of drugs that may inhibit platelet aggregation and clotting must be eliminated.

For 2 days prior to surgery, patients are requested to use an antibacterial facial cleanser for face washing when an external incision is planned and mouthwash 3 times daily when an intraoral incision is planned.

Whether a local or general anesthetic is planned, patients must have nothing by mouth for at least 8 hours prior to surgery.

Technically, essentially 2 surgical approaches are available, the intraoral and the external (submental). The author prefers the external or submental approach for a number of reasons. It reduces the incidence of postoperative infection, and the patient's healing process is simpler, shorter, and easier. ^[10] The disadvantage, of course, is the presence of a visible, albeit small, scar in the submental region.

As mentioned earlier, many types of implants and implant materials are available. However, probably the most commonly used alloplastic chin implant is made of pliable solid silicone. These implants are available in a variety of shapes and sizes. In general, the most natural and appropriate of these for routine chin enhancement is in the anatomic shape.

The surgery routinely is performed on an outpatient basis. Either local or general anesthesia is suitable, although the author prefers a general anesthetic because it provides a more controlled and predictable situation.

Following induction of anesthesia, infiltrate the planned incision site and surrounding area of dissection with a local anesthetic agent with epinephrine (usually 0.5% lidocaine with epinephrine 1:200,000). This provides hemostasis, but it also reduces the magnitude and/or depth of general anesthesia necessary. Next, wash the facial region with a mild soap (eg, Castile soap, baby shampoo) and paint the chin region with topical antiseptic solution.

Submental approach

See the list below:

• Place the incision just inferior to the natural submental crease. Placement in the crease leads to a depression and ultimately may produce a witch's chin deformity.

• Placing some traction superiorly, proceed with the dissection through the soft tissue to the inferior surface of the chin (mentum) and at the insertion of the mentalis muscle.

• Incise the periosteum and, using a periosteal elevator, develop a subperiosteal pocket. The pocket's position, whether directly over the leading edge of the chin (as is most often the appropriate location) or slightly above toward the labiomental sulcus on the flat surface, is determined by the desired or needed improvement. Approximating the size and preferred position of the implant by employing sterile implant sizers is useful. Laying a sizer over the chin and outlining it on the skin allows the surgeon initially to dissect a pocket that is not excessively large. Anatomically shaped sizers are meant to be resterilized for repeated use. With the pocket developed, the sizer then can be inserted into this space to obtain a general idea of the best implant size.

• Once a determination is made and an implant is selected, any additional necessary dissection can be performed.

• When performing the dissection, keep the elevator against the surface of the bone at all times. The pocket should extend just to the inferior edge of the mandible.

• Take care to avoid slipping below this edge or into the soft tissue inferiorly or lateral for fear of injury to the marginal mandibular nerve. This nerve, a branch of the facial (seventh cranial) nerve, travels inferior to the edge of the mandible until it crosses the mandible just anterior to the mid point of the horizontal ramus of the mandible. Technically, while dissecting with the periosteal elevator, keeping the index finger of the opposite hand on the inferior border to guide and ensure the elevator's position at all times is helpful.

• The mental nerve emanates from the bone approximately 1 cm above the edge of the mandible and approximately 2.5-3.5 cm from the mid line. It should be visible, with retraction, through the submental incision. Keeping this in mind, avoiding injury to either nerve in the dissection should be possible.

• Position the implant inferior to the mental nerve. Once the pocket is developed and bleeding is controlled, irrigate the space with topical antiseptic solution and insert the sterile implant into the space. Handle the implant minimally.

• Once the implant is in place, any adjustments to pocket dimensions or implant position can be made. The blue marker that delineates the middle on most implants facilitates positioning of the implant in the mid line. Align this point with the central mental tubercle. Close the wound.

• The author prefers to place a central suture that begins the closure of the periosteum through the implant to stabilize it in position. The wound usually is closed in multiple layers with a final intradermal pullout suture for the skin.

• Dress the wound with Steri-Strips; other Steri-Strips or tape can be used to support the area. No other dressing is necessary.

Intraoral approach

Coburn states, "Since Converse (1950) demonstrated the safety and feasibility of introducing autogenous bone grafts through intraoral incisions, this approach has been widely used." ^[1]

• Prepare the mouth with mouthwash for several days.

• Following induction of anesthesia, instill local lidocaine with adrenaline into oral mucosa in the buccal-gingival sulcus and for approximately 1.5 cm above the sulcus on the labial side and into the adjacent gumline. Then, reprep the mouth with topical antiseptic solution.

• Make an incision on the labial side of the sulcus, leaving a cuff of labial mucosa to create a secure closure. The mucosal incision should be transverse.

• While many surgeons perform the rest of the dissection via a transverse incision through muscle to bone, consider making the muscular incision and/or dissection vertically and then dividing the midline raphe of the mentalis muscles vertically.

• Rapidly proceed with the dissection to the bone and create a subperiosteal pocket. The dissection is similar to the external approach. Be careful to dissect inferiorly enough to make the pocket extend along the inferior edge of the mandible.

• It must be clear that the soft tissue and musculature are released sufficiently so that the implant is seated properly in the desired position along the inferior border of the chin.

• With bleeding meticulously controlled, irrigate the space with topical antiseptic solution and insert the selected implant.

• Close the space in a multilayer fashion including periosteum. For the mucosal closure, select a suture that is soft, pliable (eg, silk, Vicryl), and nonirritating to the gums.

Postoperative instructions include the following:

• Eat a soft diet.

• Elevate the head of the bed or use 2-3 pillows.

• Limit touching or manipulating the chin area.

• Practice good oral hygiene (for patients with intraoral approach).

  • Gentle irrigation with antiseptic mouthwash and lukewarm water 2-3 times daily

  • No use of toothbrush around lower central incisors

  • Keep tongue away from incision

• Take prescribed antibiotics for 1 week.

• Tale pain medication as needed.

• Continue normal (but not strenuous) exercise for 2 weeks.

Remove sutures 5-7 days postsurgery for external sutures and 7-10 days postsurgery for intraoral sutures.

Provide follow-up care as appropriate for any aesthetic surgical patient. Generally, barring any unforeseen circumstances or complications, see the patient weekly for the first month, then at 3 months, 6 months, and 1 year postsurgery. Subsequent follow-up care or recall is on an as-needed basis.

Complications of this surgery can be divided into those that are immediate and those that occur weeks or years later.

Immediate complications

See the list below:

• Bleeding: Bleeding can occur within hours to several days postoperatively with the formation of a tense or expanding hematoma that threatens the integrity of the skin overlying the implant. This necessitates surgical exploration with evacuation of hematoma and control of bleeding.

• Nerve injury with either paralysis or loss of sensation: Injury to one or both mental nerves causes alteration or loss of sensation of the chin and lower lip on the injured side(s). Realistically, no other action can be taken but to wait and observe whether sensation returns. This may take days to several months. However, one cause of anesthesia is malposition of the implant with pressure on the mental nerve. If the end of the implant on the anesthetic side is not palpable in the correct position, surgical exploration may be indicated after several weeks of persistent anesthesia.

• Paralysis: Injury to one or both marginal mandibular branches of the facial nerve results in paralysis. To cause such an injury, dissection would have had to be inferior to the lower mandibular border and off the surface of the bone. Even then, the injury is likely to cause only transient neurapraxia. Obviously, if a nerve transsection may have occurred, initiate immediate microsurgical nerve repair.

• Malposition of implant: This problem should be infrequent as an immediate complication, since the implant has sufficient landmarks and markers so that with direct vision placement of the implant, the exact placement of the implant should be clear.

Delayed complications

See the list below:

• Infection: Infection following mentoplasty, especially using the external incision, is quite unusual (< 1%). As expected, infection is more common when the intraoral route is used. Incidence also is higher with certain implant materials than with others; it is lowest with commercially produced solid silicone implants. Solid silicone implants that have been carved by the surgeon from a block of silicone have a higher incidence of infection, as do porous implants such as those made of Teflon, Dacron, Mersilene, Gore-Tex, and similar materials. Infection around implants is not eliminated by antibiotic therapy; thus, remove the implant. Reimplantation can be performed at a later date once all evidence of infection is gone. This may be several weeks to 3 months later.

• Postinfection deformity: Chin deformity following implant removal has been reported. Therefore, planning reimplantation following resolution of infection or subsequent osseous genioplasty (sliding genioplasty) may be important. ^[11]

• Malposition: Besides malposition immediately following surgery caused by technical error, the forces of scar capsule formation around the implant can cause movement leading to malposition.

• Implant extrusion: This is an unusual complication of inadequate soft-tissue coverage; it is more likely to occur with an intraoral incision, especially if inadequate dissection of the pocket along the lower border of the chin occurred.

• Implant mobility: Together with the natural formation of a periprosthetic capsule, subperiosteal dissection should keep the implant immobile.

• Bone resorption: This phenomenon probably occurs with all types of chin implants. However, according to Terino, "… studies have failed to reveal pathologic, functional, or even aesthetic consequences."

The aesthetic results of mentoplasty with alloplastic implants are almost universally good. This includes objective improvements in appearance and patient satisfaction.

A retrospective study by Lutz et al reported that among 24 high-density, porous polyethylene facial implants (including three chin implants) placed for augmentation in 14 patients, no hematomas, infections, migrations, or hypoesthesia was observed. Although two implants were removed because the aesthetic results were not satisfactory, of 11 patients surveyed, 82% were strongly satisfied with their overall outcome. Mean follow-up was 41 months. ^[12]