Genioplasty Treatment & Management

Alloplastic implants can be placed as an office procedure or in outpatient surgery. Common implant materials include Supramid, Mersiline, Gore-Tex, and silicone. Other options include autogenous or homologous (cadaveric) cartilage or bone, although these latter materials have a higher infection rate than is observed with autografts.

For patients undergoing sliding genioplasty, complete cephalometric tracings and measurements. Perform bony measurements and soft tissue analyses in the standard fashion. The cephalometric evaluation includes measurements of sella-nasion-subspinale A-point of the maxilla (S-N-A) and sella-nasion-supramentale B-point of the mandible (S-N-B) angles to provide information on the sagittal relationship between the anterior skull base and the maxilla and mandible, respectively.

Obtain soft tissue and lip-profile information by drawing a line perpendicular to the Frankfort horizontal plane (P-porion through O-orbitale) and through the subnasale point (sn). Measure the outline of the vermilion of the upper lip (vu), lower lip (vl), and the soft tissue pogonion (pg) in relationship to this line (reference range values: vu = 0 ± 2 mm, vl = -2 ± 2 mm, pg = -4 ± 2 mm), as depicted in the image below.

Determine the vertical height of the face by employing the method described by Powell and Humphreys.^[3] The middle one third of the face, from nasale (n) to subnasale (sn), should be 43% of the vertical height of the total lower two thirds of the face; whereas the lower one third of the face, from sn to soft tissue menton (m), should be about 57% of the total lower two thirds of the face. Also, to have 0-3 mm of maxillary incisal show in repose is acceptable. Beyond this point, maxillary vertical excess is suspected.

Assess asymmetry in the transverse dimension by using standard photographs on frontal view along with the AP cephalometric radiograph. Asymmetry may exist for various reasons, and appreciating asymmetry preoperatively is crucial. Asymmetry can be easily corrected with an offset (transverse) genioplasty, but employ care to maintain the midline to prevent an iatrogenic asymmetry postoperatively.

Once deficiencies have been measured, plan the movement. The literature shows the ratio of correlation from bone to soft tissue movement is 1:0.6-1. More recent studies show the ratio to be about 1:0.9 for horizontal movements up to 8 mm. Beyond this length, muscular and soft tissue forces are thought to cause resorption. Also, literature reports less predictability in vertical movements. With alloplastic implants, on the other hand, preoperative measurements usually allow an accurate proper size to be implanted.

Local anesthesia is used to block the mental nerves and is also infiltrated locally as a field block.

Alloplastic augmentation

For alloplastic augmentation, surgical approach options include a submental or an intraoral sulcus approach. A submental incision allows for other adjunctive procedures, such as cervical liposuction and effacement of platysmal banding, to be performed through it. On the other hand, an intraoral incision precludes a facial scar.

With either approach, carry the dissection down to the level of the periosteum. Take care to preserve and not traumatize the mental nerves. Mark the midline with a suture and place the lateral third of the implant subperiosteally, as depicted in the 1st two images below. Once the implant is in proper position, close the soft tissue in layers, paying special attention to the reattachment of the mentalis muscle to avoid a ptotic lower lip (ie, witch's chin deformity). Redrape the soft tissue with tape and schedule a follow-up visit with the patient within one week of surgery. The procedure should take around 15 minutes to complete, as depicted in the last two images below.

Sliding genioplasty

For patients undergoing sliding genioplasty, admit to the hospital only if orthognathic surgery is performed. Otherwise, the procedure can be performed in an outpatient setting even when concomitant procedures, such as rhinoplasty or liposuction, are performed. The sliding genioplasty can also be performed under local anesthesia or in an outpatient setting with good results; however, general anesthesia is most commonly used with this procedure. Patients are more comfortable, and the airway is better protected under general anesthesia. Unless a rhinoplasty is performed concurrently, nasotracheal intubation is preferred.

Like many surgeries in the head and neck, preservation of a named nerve along with strict attention to hemostasis is the key to a successful operation. In making the gingivolabial sulcus incision, leaving an adequate cuff of mucosa along with a good part of the mentalis muscle for later resuspension is crucial; this technique leads to avoidance of lower-lip ptosis, as depicted in the image below.

Subperiosteal dissection is carried out laterally to identify the mental nerve, as depicted in the 1st image below. The foramina of the nerve are generally found between the first and second premolar teeth at the level of the origin of the mentalis muscle or 2-4 mm below the level of the bicuspid teeth apices. The foramina are situated deep to the midportion of the depressor anguli oris. Dissect inferolaterally to allow for a longer osteotomy, preventing unsightly mandibular notching. Leave the periosteum at the inferior rim intact. Align the skeletal midline with the overlying soft tissue corollary. Use a sagittal saw with a 30-degree bend to facilitate an even cut while minimizing soft tissue trauma, as depicted in the 2nd image below. Lateral cuts should be 4-5 mm below the foramina to compensate for the path of the inferior alveolar nerve.

Perform double osteotomies in the same manner. Plan asymmetric cuts well in advance. Fixation can be achieved with wires or plates. Wire fixation may lead to increased resorption because of greater periosteal dissection and a possible drop of the anterior segment from muscle pull. Great success has occurred using a single 4-hole titanium plate with 12-mm screws for males and 10-mm screws for females. Each plate is marked with the amount of movement obtained on the face of the plate, as depicted in the image below. Resorbable plates have also been used by oral and maxillofacial colleagues. Closure is accomplished in multiple layers. Resuspend the mentalis with 3-0 interrupted buried Vicryl sutures and close the mucosa with a running 3-0 chromic suture.

Mentum reduction

This procedure can be performed in a similar manner to which a sliding genioplasty is performed, as described above. However, instead of advancement, the distal segment of bone is retruded and secured. Additionally, through either an intraoral or a submental incision, direct reduction of the prominent chin may be accomplished. Access should be wide enough to allow for an even reduction of the inferior border of the mandible, 1 cm lateral to the mental foramen, as depicted in the image below.

Redrape the skin at the level of the labiomental fold with Mastisol (Ferndale Laboratories, Ferndale, MI) and Steri-Strip tape. Advise patients to stay on a soft diet and to rinse frequently with saline solution until the first postoperative visit. In the experience of the authors, the surgical time for the osseous genioplasty procedure ranges from 15-105 minutes, with an average surgical time of about 45 minutes. The alloplastic implantation is roughly 25% shorter in operative time. Chin reductions are equivalent in time to the genioplasties.

Schedule a follow-up visit with the patient on postoperative days 7 and 14.

Each of the procedures described has unique advantages, disadvantages, and complications.

Alloplastic mentoplasty may cause bone resorption, infection, extrusion, dehiscence, overprojection or underprojection, asymmetry, displacement, capsular contraction, lower-lip retraction, and chin ptosis. Studies show that resorption occurs to some extent in many, if not all, patients. One study showed up to 5 mm of resorption at 48 months after surgery. Resorption has been attributed to subperiosteal placement of the implant. Tension in the soft tissue pocket due to pressure from the overlying skin or mentalis musculature has been thought to cause this pressure resorption. The overall soft tissue profile, however, is not usually affected by this bone resorption. Reporting evidence to the contrary, a 1999 study on adult hounds by Pearson and Sherris showed no significant difference between supraperiosteal and subperiosteal placement of silastic implants.^[4]

Osseous genioplasty has its own set of complications. Mental nerve injury, malunion, nonunion, irregularities, step-type deformities, lip drop, and overcorrection or undercorrection have been reported. Of note, undercorrection is better accepted than overcorrection in which the chin placed forward to the lower lip can yield a disharmonious profile. In a 10-year series, Hoenig reported that in the single sliding osteotomy group, no major branches of the mental nerves were transected. Paresthesia was only transient, usually lasting for only a few weeks. All who had only a single genioplasty recovered totally from a neurosensory deficit.^[2]

Reduction genioplasty has a similar set of complications as those observed in advancement sliding genioplasties.

Strict attention to treatment planning and surgical technique can prevent most of these problems. Augmentation of the chin properly performed, either as a lone procedure or in conjunction with other procedures, yields an aesthetically pleasing result.

Whether an alloplastic implant or an osseous implant is used, more than 90% of the patients are satisfied with their results. Complications observed with genioplasty are minimal, and benefits are readily evident to both patient and surgeon.

In addressing the underprojected chin, alloplastic implants and sliding genioplasty are generally considered equally acceptable. The benefits of the sliding genioplasty include its versatility in correcting chin abnormalities in every dimension and its relative ease of use. For chin reductions, a genioplasty or a direct reduction can result in a better profile. For the mild-to-moderate deficiency of the chin, alloplastic implantation is simple, easy to place, and requires only short operative time. Excellent results are obtainable, surgical time is acceptable, and patient satisfaction can be achieved with both alloplastic implants and sliding genioplasty. Additionally, the protruding chin can be addressed by either the genioplasty or by direct reduction.

The stability and predictability of skeletal surgery has been recently reconfirmed by Proffit and Turvey.^[5] In addition, more advance mandibular skeletal surgeries have been introduced by Puricelli.^[6]

The authors hope that these techniques are widely taught in residency training programs as methods to achieve a desired cosmetic result of the mentum area.