Practical Plastic Surgery

muscle strain from the forces needed to close the interlabial gap. The treatment for this type of facial anomaly may be to reposition the maxilla superiorly, particularly in the posterior area.

Maxillary sagittal hyperplasia is extremely rare. Patients may complain of a small chin as well. Once again, this is most likely a case of pseudomicrogenia, where the chin appears relatively small due to the prominence of the maxilla in the sagittal plane. These patients will have a convex facial profile associated with maxillary protrusion and an acute nasolabial angle. This form of microgenia can be corrected with repositioning of the maxilla, after which a decision can be made on the need for an adjunct genioplasty.

Evaluation of the Mandible

After a thorough investigation to rule out any maxillary discrepancies, the next step is to evaluate the mandible. For a patient with mandibular hypoplasia with either gross malocclusion or severe hypoplasia (greater than 4 mm), a formal orthognathic work-up is necessary. The risks of advancing or augmenting a chin greater than 5-6 mm include an unnatural appearance, a deep labiomental angle, and the risk of advancing the chin point past the lower central incisor. Severe mandibular sagittal hypoplasia is corrected with a BSSO, and genioplasty should be viewed as an adjunct procedure. Prognathia in the setting of class 3 malocclusion should be corrected by a setback with a BSSO. Isolated true macrogenia in the presence of a normal class 1 occlusion can easily be treated with a genioplasty, setting the chin point back and even reducing chin height if needed.

Indications for Isolated Genioplasty

After careful scrutiny of the skeletal, dental and soft tissue structures, there exist certain cases that are amenable to isolated genioplasty. An isolated genioplasty can be considered if functional occlusion is present and the lower third profile has mild hypoplasia or hyperplasia in the sagittal or vertical plane. A sagittal hypoplasia (3-4 mm) in the setting of functional normo-occlusion with acceptable facial proportions is an ideal candidate for AHMO with advancement. A variation of the standard sliding genioplasty is the “jumping” genioplasty. The “jumping” genioplasty is ideal for sagittal advancement when vertical reduction is needed.

Patients who are considered for isolated genioplasty should have a good overall profile and occlusion. The surgical goals for these patients include creating an aesthetically pleasing facial contour and establishing proportionate facial height. Ideal candidates for a genioplasty are: (1) retrogenia, i.e., recessed chin point with class I occlusion; (2) mild retrognathia (≤4 mm) with a functional occlusion; and (3) macrogenia.

For example, in a patient that may have a long lower third of the face, a reduction genioplasty is performed to reduce the vertical dimension of the chin. Verti-

65cal reduction is done by performing a second horizontal osteotomy that is parallel to the first osteotomy, and a segment of bone is removed. Another indication for an isolated genioplasty may be a mild asymmetry, when the chin does not coincide with facial midline. An oblique triangular wedge of bone can be removed from one side and transplanted to the other side to correct chin asymmetry. In all cases, the chin has to be rigidly fixed by miniplates, wire or screws. A variety of genioplasty is the “jumping” genioplasty. This type of procedure allows the surgeon to both increase the chin projection and shorten the vertical dimension of

the chin simultaneously. After the osteotomy is completed, the basilar segment is elevated on top of the upper symphysis.

Surgical Technique

Genioplasty can be performed under local anesthesia with IV sedation or under general anesthesia. General anesthesia is more commonly used with this procedure. Lidocaine with epinephrine is infiltrated along the depth of the buccal vestibule. An incision is made in the buccal vestibule, initially perpendicular to the mucosa then perpendicularly to the muscle and bone. The dissection is continued in the subperiosteal plane to identify the mental foramen on both sides. After identification of the mental foramen, the mental nerves should be protected from both direct and traction injury. The osteotomy is done under the apices of the teeth and the mental nerve. Upon completion of the osteotomy, the chin is then rigidly fixated. A step-off (sharp edge) at the posterior part of the genioplasty should be avoided. The contour of the mandible should be smooth. There are a variety of techniques used for fixation of the chin including wires, resorbable or titanium bone plates. Closure should be done in multiple layers. The mentalis muscle must be reapproximated. The muscle layer can also be reattached to the chin using Mitek anchors. We prefer using two Mitek anchors to secure the mentalis muscle to bone. Alternatively, simple reapproximation with two horizontal mattress sutures is acceptable. This prevents ptosis of the mentalis muscle. Nonfixation may result in a “witches chin.” A compressive chin dressing is worn for 5 days postoperatively. The oral mucosa is closed with a running 3-0 chromic suture. The advantage of this procedure is its versatility, reliability and reproducible correction of chin point discrepencies. The disadvantages, when compared to alloplastic augmentation, include increased operative time, bleeding and incidence of mental nerve hypoesthesia.

Chin Augmentation Using an Alloplastic Implant

An alternative to genioplasty in correcting chin hypoplasia is the use of a chin implant. The use of implantable biomaterials and devices plays a potential role in most forms of reconstructive surgery. The common locations for alloplastic augmentation are the chin and malar regions. There are numerous synthetic implantable materials that can be classified as carbon based polymers, noncarbon-based polymers, metals and ceramics. This wide selection allows the surgeon to choose a material tailored to the individual needs of the patient. Silicone (silastic), a noncarbon-based polymer, was one of the first materials used in facial implants. Silicone is resistant to degradation and when fixed against a bony surface its long term stability is very high. Carbon-based polymers include polytetrafluoroethylene (PTFE), polyethylene (PE) and aliphatic polyesters. PE is currently being used in its high density form (HDPE), which allows for contouring by the surgeon. The solid implantable form of HDPE (Medpor®) allows for increased fibrous ingrowth lead-

ing to long-term stabilization of the implant. 65 Alloplastic chin augmentation is a well-accepted technique used in the correc-

tion of mild retrognathia or true retrogenia. The advantages of alloplastic augmentation include the material being readily available without donor morbidity, shorter operating time and less blood loss. The disadvantages include bone resorption, infection, extrusion and displacement.

When an implant is used, either an intraoral or extraoral approach can be used. With the extraoral approach, the incision placement is in a natural crease location.

The extraoral approach has a lower rate of infection although it is more difficult to achieve precise placement of the implant. The intraoral technique introduces oral flora into the pocket of dissection, increasing the risk of infection and extrusion.

Malar Augmentation

The malar prominences contribute to aesthetic balance and beauty. Deficiencies or asymmetry in the malar region are usually secondary to trauma, congenital anomalies, such as Treacher Collins syndrome, cancer, or aging. Malar augmentation can be used in either aesthetic or reconstructive practices to achieve symmetry and balance of the face. For example, patients that have undergone repair of a cleft lip and palate may require a LeFort I osteotomy to correct midface deficiency and malocclusion. Correction of the occlusion can be done with the LeFort I osteotomy. The concave profile can be enhanced by malar augmentation (or doing a high osteotomy) to help reestablish overall facial harmony and proportions. In the aging patient, the face may have a tired appearance due to resorption of the maxilla and descent of the malar fat over the zygoma. Malar augmentation may help to create a more youthful appearance.

Preoperative assessment of the deficient or asymmetric malar region is important prior to any augmentation. The facial skeleton can be analyzed using three-dimensional CT generated models from which custom-made implants can be fabricated. Any asymmetries found should be pointed out to the patient and documented. Malar augmentation can be done with autologous bone or with alloplastic implants.

Technique

A number of approaches have been described, including the lower eyelid, coronal, temple and preauricular incisions. However, the most popular approach is by an intraoral incision. This approach leaves no visible scar and allows the procedure to be performed under local anesthesia if desired. The intraoral approach is done through an upper buccal sulcus incision followed by subperiosteal dissection of a pocket in the malar region. It is important to identify the infraorbital nerve and protect it. The implant is contoured and placed after creation of an adequate pocket. It should remain “uncontaminated “during its placement in order to decrease the risk of infection. In the no touch technique, the implant does not come in contact with gloved hands, skin, or oral mucosa in hopes to decrease any bacterial contamination load. Finally, the implant should be secured with either screws, nonabsorbable sutures, or held in place by a tight pocket of periosteum.

Pearls and Pitfalls

Over the long-term, genioplasty is much more durable than alloplastic augmentation of the chin. At some point, most implants will require replacement due to malposition, extrusion, infection or overlying soft tissue changes. Osseous genio-

65 plasty, however, can last a lifetime. It is important to discuss this with the patient. When designing the proposed osteotomy for genioplasty, one has to pay particu-

lar attention to the apices of the teeth and the mental nerve. The intraoral approach provides a simple access without a visible scar. The mental foramen lies on the same vertical plane defined by the second bicuspid tooth, infraorbital foramen and pupil. The mental nerve should be dissected out, retracted superiorly and protected during the osteotomy. The three branches of the mental nerve exit the mental foramen and

supply general sensation to the chin point. The osteotomy line should be about 3 mm below the mental canal to avoid the route of the inferior alveolar nerve.

Genioplasty by AHMO has also found a functional role in patients with obstructive sleep apnea. Advancement of the genioglossal muscle leads to indirect elevation of the hyoid, thus serving as an adjunct to bimaxillary surgery. A long distance (>15 mm) from the hyoid to the mandibular plane angle can contribute to a decrease in the posterior airway space. By advancing the genial tubercle and muscles, this will indirectly pull the hyoid closer to the mandibular plane and away from the posterior airway.

Suggested Reading

1.Chang EW, Lam SM, Karen M et al. Sliding genioplasty for correction of chin abnormalities. Arch Facial Plast Surg 2001; 3(1):8.

2.Constantinides MS, Galli SK, Miller PJ et al. Malar, submalar and midfacial implants. Facial Plast Surg 2000; 16(1):35.

3.Millard DR. Chin implants. Plast Reconstr Surg 1954; 13(1):70.

4.Spear SL, Kassan M. Genioplasty. Clin Plast Surg 1989; 16(4):695.

5.Spear SL, Mausner ME, Kawamoto Jr HK. Sliding genioplasty as a local anesthetic outpatient procedure: A prospective two-center trial. Plast Reconstr Surg 1987; 80(1):55.

6.Wolfe SA. Chin advancement as an aid in correction of deformities of the mental and submental regions. Plast Reconstr Surg 1981; 67:5.

7.Yaremchuk MJ. Facial skeletal reconstruction using porous polyethylene implants. Plast Reconstr Surg 2003; 111(6):1818.

65

Preoperative Planning

History and Physical

The importance of the initial consultation cannot be overemphasized. Determining breast volume, selecting the type and shape of the implant, deciding on placement (subglandular or submuscular) and choosing the surgical approach should all be discussed. Evaluation of anatomic features is an essential element when planning augmentation. Noting asymmetry is important because the patient may be unaware of the problem. In such cases, the surgeon should explain that efforts to correct asymmetry will be attempted, but that perfectly symmetric results are unrealistic. Attempting to meet the patient’s expectations regarding size without compromising a natural appearance is very important. In young healthy patients, routine blood tests are not required. It is, however, important to rule out a personal or family history of clotting disorders. A urine pregnancy test should be performed in most cases.

Choice of Incision

The trend in plastic surgery is to minimize scarring by remote placement of access incisions. The position of the incision is important and should be individualized since no single incision works best for all patients. Most surgeons have their own preference as to the surgical approach used in the procedure. In addition, most patients are knowledgeable about the various incisions and have their own preferences as well. The choice of incision should be discussed with the patient in a nonbiased manner highlighting pros and cons of each approach (Fig. 66.1). Currently, there are four commonly used types of incisions: periareolar, inframammary crease, axillary and umbilical. Some patients are candidates for an endoscopic transaxillary or inframammary approach; however results depend in part on the surgeon’s familiarity and experience with endoscopic techniques.

Type of Implant

Silicone gel-filled implants were the most common implants used prior to their removal from the market by the Food and Drug Administration (FDA) and are available only through FDA approved clinical trials. Currently, saline-filled implants are the type of implant most widely used. They can be classified as smooth or textured, round or contoured and as having a high or low profile.

Cancer Detection

It is important to educate patients about the potential long-term effects on breast cancer surveillance. A woman’s risk of developing breast cancer is not affected by breast implants, and to date there is no evidence to support a relationship between silicone or saline implants and breast cancer in humans. Slight modifications in mammographic technique (Eklund displacement technique) may be required for adequate visualization of all breast tissue. Capsular contracture has the greatest im-

pact on mammography. Severe contracture can reduce the accuracy of the mammo- 66 graphic findings. Current recommendations suggest women aged 30 or older should

have baseline and postaugmentation mammograms and should follow the same schedule of routine mammography as all other women. They should also perform monthly self-exams and become familiar with the new feel of their breast tissue. Self-exams are much more likely to detect a breast cancer in augmented patients compared to nonaugmented women.

Figure 66.1. Commonly used incisions for breast augmentation.

Sensation

Breast and nipple sensation are usually compromised only temporarily (weeks to months) due to nerve stretching from aggressive lateral dissection. Accidental nerve division is uncommon. With the subglandular approach, the reported incidence of nerve injury is 10%, and even lower with the submuscular approach. The degree of sensation loss is directly proportional to the size and diameter of the implant due to the large pocket that must be dissected. Impaired breast sensation is more likely after secondary procedures, especially extensive capsulotomy which may subject sensory nerves to injury.

Pregnancy and Lactation

Many women seek breast augmentation prior to their childbearing years. Breast augmentation is extremely unlikely to impair lactation or breast-feeding, especially when implants are placed in the submuscular position. Many surgeons will advise patients to undergo breast augmentation a minimum of 6 months prior to pregnancy or at least 6 months after the termination of lactation. Breast appearance after childbirth varies in patients who have had augmentation prior to pregnancy. Some will return to their prepregnancy appearance while others do not.

66 Intraoperative Considerations

Inframammary Incision

This is the most common approach for placement of a breast implant. The incision is made just above the imframammary crease, and should be no more than 3-4 cm in length. The surgeon must estimate where the incision will sit in relation to the crease created by the larger enhanced breast. An incision placed too low may be obviously visible. The inframmary incision is a favorite among surgeons because it