Contraindications

Severe microgenia is a contraindication to augmentation mentoplasty and may suggest the need for orthognathic surgery. Other relative contraindications can include severe malocclusion, labial incompetence, lip protrusion, shortened mandibular height, and periodontal disease.

Preoperative planning

Chin augmentation is frequently done in conjunction with other procedures, such as rhinoplasty or rhytidectomy. Since chin projection is best viewed in profile, many patients are unaware of deficiencies when seeking consultation to improve their submental or nasal appearance. It is important for the astute facial plastic surgeon to always consider chin projection or irregular mandibular contour, and explain the significance to the patient in order to obtain an optimal, balanced result (Figure 3).

Preoperative photography with a minimum of frontal, lateral, and oblique views, ensuring that the patient is placed in the Frankfort plane, is essential for photodocumentation of the patient’s preoperative appearance and for implant sizing. Computer simulation is a useful tool to demonstrate the benefit of chin augmentation, especially for those patients who do not seek improvement in this area during their initial consultation (Figure 4). Preoperatively it is important for the surgeon to identify, document, and discuss with the patient any existing asymmetry, which otherwise may only be noticed by the patient
after surgery. Also mandatory is a preoperative assessment and discussion of occlusion with the patient, since alloplastic implants will not affect the patient’s occlusal status. Any desire by the patient to functionally improve malocclusion would be more appropriately addressed by orthognathic surgery.

Figure 4 This series of images shows (A) preoperative appearance, (B) the potential benefit of a rhinoplasty alone, and (C) a rhinoplasty with a chin implant using computer imaging

Figure 4 This series of images shows (A) preoperative appearance, (B) the potential benefit of a rhinoplasty alone, and (C) a rhinoplasty with a chin implant using computer imaging

It is most important to fully discuss the risks of surgery, especially paresthesia of the chin and lower lip. These are frequently resolved within 6 weeks of surgery, but can persist for months. Rarely, some numbness of a portion of the chin and/or lip may persist permanently.

The authors’ preferred set-up for this operation includes a double hook skin retractor, scalpel, cautery, an 8 mm ribbon retractor, a 6 mm and 8 mm periosteal elevator, two straight clamps, and an antibiotic solution (20 ml of 40 mg/ml Gentamicin in 100 cc normal saline) to bathe the implant and instruments prior to insertion (Figure 5).

Figure 5 Instruments used in chin implant placement are (from left to right): a blunt Senn skin retractor, a 6 mm periosteal elevator, an 8 mm periosteal elevator, two straight Kelly clamps (only one is shown in image), and an 8 mm ribbon retractor

Figure 5 Instruments used in chin implant placement are (from left to right): a blunt Senn skin retractor, a 6 mm periosteal elevator, an 8 mm periosteal elevator, two straight Kelly clamps (only one is shown in image), and an 8 mm ribbon retractor

Implant selection

The implant of choice is a solid but flexible silicone elastic polymer (Silastic, Dow Corning, Midland, MI). A number of additional alloplastic implants and augmentation materials are available and should be considered, but a full discussion of these products is beyond the scope of this article. Within the body, Silastic is non-reactive and is surrounded by a fibrous capsule. Fenestrated Silastic implants are further stabilised by tissue ingrowth. If indicated, the surgeon may further modify Silastic implants by trimming the projection or edges with conventional instruments.

A number of Silastic mandibular implants are available commercially. Most importantly, the physician should choose an extended mandibular implant rather than a central chin implant, as central chin augmentation alone can result in an unnatural, pointed chin and poorly defined jawline. Central chin implants also frequently migrate, creating asymmetry (Figure 6). Properly designed extended mandibular implants have tapered ends that provide a smooth transition from the central mentum to the lateral mandible, preserving the natural jawline.

Some of the most commonly used implants are the extended anatomical mandibular implant, the Mittelman Pre Jowl-Chin™ implants (Implantech Associates Inc., Ventura, CA), the Mittelman Pre Jowl® implants (Implantech Associates Inc.), the Terino Square Chin implants (Implantech Associates Inc.), and the Flowers Mandibular Glove® implants (Implantech Associates Inc.). Each implant is available in a number of sizes and configurations and can all provide excellent results8. The extended anatomical mandibular implant provides uniform augmentation of the prejowl area with varying degrees of central chin augmentation. The Flowers mandibular implants provide a variation in the tilt of the implant at the central mentum with a tapered extension along the mandible. The extended prejowl–chin implant provides four progressive variations in size of central mentum augmentation with a comparable increase in thickness in its lateral extensions, which provide augmentation to the prejowl area, without affecting chin projection (Figure 7). In the author’s hands, this implant has proven invaluable for the facelift patient with adequate chin projection but a significant prejowl sulcus. In another modification, the Terino square chin implant has a more squared anterior projection and can be especially suitable for select male patients.

Figure 6 Central chin implants frequently migrate, as shown in this patient. The chin implant position has been outlined

Figure 6 Central chin implants frequently migrate, as shown in this patient. The chin implant position has been outlined

Surgical technique

This procedure can be performed under either local or general anaesthesia. If the patient is placed under general anaesthesia, the endotracheal tube should be secured to the central incisors. The submental incision is generally first marked immediately anterior to the submental crease to decrease the risk of a depressed scar and accentuated submental crease. The midline is marked at the pogonion and should line up with the midline of the submental incision, midline of the lips, central incisors, and nasal collumella (Figures 8a and 8b). Approximately 5 ml of local anaesthetic (the author prefers a 1:1 mixture of 1% lidocaine and 0.5% bupivacaine, with 1:100000 adrenaline/epinephrine) is injected into the skin at the planned incision, as well as along the anterior face of the mandible to the mid-mandible body on either side. The instruments and implant are soaked in a solution of gentamicin (20 ml of 40 mg/ml IV gentamicin solution in 300 ml saline) in preparation for use.

A 3–4 cm transverse incision is made at the submentum with a 15-blade scalpel. Dissection then proceeds in the same transverse plane, using either monopolar cautery or a scalpel until reaching the periosteum at the anterior surface of the mandible (Figure 8c). A scalpel is then used to incise the periosteum transversely. A small periosteal elevator is used to

Figure 7 The Mittelman Pre Jowl-Chin™ implant (top) and the Mittelman Pre Jowl® implant (bottom) demonstrate prejowl augmentation with or without central chin augmentation

Figure 7 The Mittelman Pre Jowl-Chin™ implant (top) and the Mittelman Pre Jowl® implant (bottom) demonstrate prejowl augmentation with or without central chin augmentation

raise the periosteum superiorly such that the superior–inferior dimension of the chosen implant can be (approximately 2–3 mm). Some surgeons advocate leaving a central portion of intact periosteum on the mandible, placing the central portion of the implant supraperiosteally with the lateral thirds of the implant placed subperiosteally, in the belief that mandibular resorption in the central area of the implant may be decreased. In the author’s experience, however, any bony resorption that occurs with central periosteal elevation does not appear to be clinically significant.

The right subperiosteal pocket is then created with a small periosteal elevator in the surgeon’s dominant hand, while using the other ‘smart’ hand to grasp the mandible at the borders of dissection (Figure 8e). Care is taken to dissect along the inferior–anterior border of the mandible, raising a precise subperiosteal pocket that is just wide and long enough to accommodate the implant while avoiding the mental foramen. Most extended mandibular implants have a 6–8 mm vertical height and should be able to be placed below the mental foramen without damaging the nerve. Because the neurovascular bundle is encased in a strong, connective tissue sheath and exits the mental foramen in a superior direction, the use of an elevator in this space may at times stretch the sheath to some degree, but is unlikely to penetrate the sheath. Once complete, a small volume of antibiotic-containing saline is poured into the subperiosteal pocket. The same technique is used on the left to create an identical subperiosteal pocket.

Figure 8: (A) This 16-year-old male with a severely hypoplastic mentum is marked for placement of a chin implant. (B) The incision for a chin implant is placed immediately anterior to the submental crease as placement within the crease may actually accentuate it. (C) The anterior soft tissues are retracted cephalically and the dissection proceeds through the subcutaneous tissue and mentalis musculature until reaching the periosteum at a level approximately 3 mm above the inferior border of the mentum. (D) The periosteum of the inferior anterior mandible is incised and elevated inferiorly a few millimeters and superiorly until the height of dissection is adequate for placement of the implant. (E) Subperiosteal pockets are created laterally along the inferior border of the mandible, below the mental nerve and above the muscular attachments along the inferior border of the mandible. The periosteal elevator is held with the right hand and is guided with the left ‘smart hand’ technique to protect the nerve and keep the elevator in the correct orientation. Lateral dissection should extend approximately 6–7 cm from the midline, depending on the implant. (F) After soaking in gentamicin solution, the implant is placed in the subperiosteal pocket using two straight Kelly clamps to guide the implant. During implant insertion, the right-handed surgeon tends to position the implant on the right side first, while the assistant holds the left half of the implant to prevent contact with the patient’s skin. (G) Once the right side of the implant is correctly inserted, the implant is folded acutely on itself and the left half is guided into the left pocket. (H) The blue line of the implant is then lined up with the blue line marking the central mentum in order to ensure midline placement. (I) Prolene is then used to secure the implant and perform a three-layered closure

Figure 8: (A) This 16-year-old male with a severely hypoplastic mentum is marked for placement of a chin implant. (B) The incision for a chin implant is placed immediately anterior to the submental crease as placement within the crease may actually accentuate it. (C) The anterior soft tissues are retracted cephalically and the dissection proceeds through the subcutaneous tissue and mentalis musculature until reaching the periosteum at a level approximately 3 mm above the inferior border of the mentum. (D) The periosteum of the inferior anterior mandible is incised and elevated inferiorly a few millimeters and superiorly until the height of dissection is adequate for placement of the implant. (E) Subperiosteal pockets are created laterally along the inferior border of the mandible, below the mental nerve and above the muscular attachments along the inferior border of the mandible. The periosteal elevator is held with the right hand and is guided with the left ‘smart hand’ technique to protect the nerve and keep the elevator in the correct orientation. Lateral dissection should extend approximately 6–7 cm from the midline, depending on the implant. (F) After soaking in gentamicin solution, the implant is placed in the subperiosteal pocket using two straight Kelly clamps to guide the implant. During implant insertion, the right-handed surgeon tends to position the implant on the right side first, while the assistant holds the left half of the implant to prevent contact with the patient’s skin. (G) Once the right side of the implant is correctly inserted, the implant is folded acutely on itself and the left half is guided into the left pocket. (H) The blue line of the implant is then lined up with the blue line marking the central mentum in order to ensure midline placement. (I) Prolene is then used to secure the implant and perform a three-layered closure

The surgeon and assistant then bathe their hands in antibiotic-containing solution in preparation for implant placement. The implant is then grasped on its right lateral end with a straight Kelly clamp and placed into the right subperiosteal pocket, while the assistant grasps the left end of the implant with another straight Kelly clamp to prevent its contact with skin and maintain strict sterility (Figure 8f). The implant should slide into place with relative ease. It is then grasped on the left lateral end, folded acutely on itself, and guided into the left subperiosteal ‘smart’ hand over the location of the mental foramen and nerve, which helps prevent insertion along a false passage above the mental foramen (Figure 8g). Proper positioning of the implant is confirmed by palpation of its lateral extensions, and midline positioning of the central portion is confirmed by lining up the blue mark on the implant with the previously marked soft tissue midline (Figure 8h). If difficulty is encountered during insertion of the implant after a pocket was created, the surgeon must identify where the obstruction lies. Most commonly, the obstruction is found immediately lateral to the central dissection zone. This is the location of the anterior mandibular ligament, which is somewhat resistant to elevation in most patients.

The chin–prejowl implant is then secured to the inferior periosteum with 3–0 Prolene (Ethicon Endo‑Surgery, Inc., Blue Ash, OH) suture to prevent migration. The superior periosteum is then re‑approximated with the inferior periosteum and sutured with interrupted 3–0 Prolene sutures. The overlying muscle and soft tissues are then closed with inverting sutures in layered fashion using 3–0 Prolene, and the skin is closed in a meticulous single layer closure with the surgeon’s preferred suture (Figure 8i). When placing a prejowl implant, the procedure is the same but 5–0 Prolene sutures are used.

Postoperative management

Patients receiving alloplastic implants are always placed on intraoperative and postoperative antibiotics. Ideally, intravenous cephazolin 1000 mg is given 30 minutes prior to incision. The patient continues on cephalexin 500 mg twice daily for 5 days postoperatively. A dressing is generally unnecessary when chin augmentation is performed as a standalone procedure, but may be used when performed with other procedures. During the healing period, the patient is instructed to avoid manipulation or pressure to the chin reinforced with steri-strips for 1 week following suture removal.