There are many materials used for alloplastic implants including silicone elastomers, expanded polytetrafluoroethylene (e-PTFE), high-density porous polyethylenes, methylmethacrylate, nylon mesh material, bioglass and alumina ceramics, and hydroxyapa- tite-calcium phosphate material [2]. Currently, the most commonly used materials are solid silicone and expanded polytetrafluoroethylene. Both materials have performed well in terms of the incidence of infection and lack of bony resorption tendencies (when positioned in the correct plane of dissection).

Improved understanding of tissue-implant interface biology has encouraged the development of bioactive implants which allow for biologic bonding of tissue to implant, which permits natural tissue regeneration as opposed to chronic foreign body or inflammatory reaction. Evolving material technologies have permitted the creation of better implants; however, the ideal alloplastic material has yet to be formulated [3]. The most significant burden still remains in accurate facial analysis, assessment, and planning to achieve a good surgical outcome.

19.2 Technique

Surgical technique affects both the short-term and long lasting outcomes in facial skeletal augmentation. General surgical principles relating to implantation technique such as avoidance of contaminated fields, use of perioperative antibiotics, and meticulous intraoperative handling of the implant materials are vital to the success and safety of the operation. Careful preoperative assessment of the recipient site should determine whether adequate vascularity and soft tissue coverage are present.

19.2.1 Midface Implants

Prominent malar eminences are a canon of beauty in many cultures, conveying the youthful appearance of facial fullness. A hypoplastic flat malar area can make the face appear tired and contributes to a prematurely aged countenance. This tired, sunken look can be secondary to midface hypoplasia and/or atrophy and ptosis of the soft tissues. It can also be

accentuated by an over-resected facelift procedure. The goal of midface augmentation is to restore the appearance of youth and beauty by enhancing structure and facial contour.

The majority of patients are unaware of the contribution the midface provides in terms of overall facial harmony; instead, many patients focus on the nose, eyes, or lax facial skin. The facial plastic surgeon can educate patients by illustrating how malar augmentation can restore a youthful and balanced facial contour. In patients lacking bony substructure, rhytidectomy alone does not provide sufficient rejuvenation. Volume restoration by means of midface augmentation in conjunction with facelift can provide the scaffolding for a more optimal redraping of facial tissues to achieve a more successful rejuvenation. Malar implantation enhances rhytidectomy or rhinoplasty results by further improving facial balance and harmony.

The majority of malar augmentations are performed on an elective basis. General indications for malar augmentation include posttraumatic and posttumor resection deformities, congenital deformities, aged face with atrophy and ptosis of soft tissues, unbalanced aesthetic facial triangle, a very round full face or a very long narrow face, and midface hypoplasia. Patients may present with changes associated with aging, such as hollowing of the cheeks and ptosis of the midfacial soft tissue. Malar implants can augment cheek hollows and grooves associated with inferior displacement of the malar fat pad and soft tissues secondary to volume depletion of aging. Patients with midface hypoplasia gain aesthetic benefit from enhanced facial volume. Patients with mild hemifacial microsomia may also show improvement. Other patients may request facial augmentation to produce a dramatic high and sharp cheek contour. Flat, thin, and round faces all benefit from malar augmentation, as it balances the face to create a more aesthetically appealing appearance.

Facial analysis, incorporating photographic documentation, is a critical component of patient selection for malar augmentation. Several techniques of facial measurement analysis of the malar region exist; however, the exact location for augmenting the malar eminence is not universally agreed upon, as the type of malar deficiency varies from patient to patient.

After the determination of appropriate implant size to be used, the patient can undergo the procedure.

The most common technique used is via an intraoral route. No external incisions are made on the face. The initial step is to adequately mark the patient, determining the planned placement of the implants. The precise anesthetic solution used is not as important, as long as it contains epinephrine. After infiltration on both sides, a 1.5 cm sublabial incision is made in the vertical direction through all layers down to the bone. Horizontal incisions for the approach are discouraged. Once this incision has been made, a periosteal elevator is used to dissect the periosteum off the bone. Many authors favor the use of fixation to help secure the implant. The author prefers to use precise subperiosteal pockets for implant placement. Therefore, wide undermining is not required, but careful, deliberate creation of pockets allows for precise localization. The infraorbital nerve is not compromised during the dissection. Depending on the implant, the lateral dissection may be extended to the zygomatic arch. Submalar implants or combined implants will necessitate a more inferior dissection from the arch over the masseter muscle. The correct plane of dissection is over the glistening white fibers of the muscle.

Prior to implant placement, an antibiotic solution is used to irrigate the cavity. A 4–0 chromic suture is passed through the lateral edge of the implant. Using an Aulfricht retractor, the lateral extent of the pocket is identified and the same suture is passed through to the skin surface. With a gentle amount of tension, the implant is inserted into the pocket. The assistant gently pulls on the suture, while the surgeon is guiding from medial to lateral direction. The suture is then gently tied over a bolster, which will be removed after 5 days.

The pocket will “shrink-wrap” around the implant over the next 24–48 h. The incisions are closed in two layers. Attention to detail during the closure cannot be overemphasized as any saliva that penetrates into the wound can lead to infection.

Besides the intraoral route, there are other approaches that may be preferred by other surgeons. The subciliary approach, through a lower blepharoplasty incision, may be used to place smaller implants, especially implants used to augment the nasojugal fold. During facelift surgery, penetration can be made through the subcutaneous musculoaponeurotic system (SMAS) and then carried down to the bone. A subperiosteal pocket can be formed from lateral to medial. This technique limits the access for implant positioning.

19.2.2 Mandibular Implants

The chin has a prominent role in anchoring facial symmetry and aesthetics. Along with the nose, it is a primary determinant of facial balance, especially in consideration of the facial profile. The features of the chin can determine characteristics of the face and even perceptions of personality where a long chin implies strength and power, and a short, small chin portrays weakness.

Abnormalities of the chin are commonly present in patients pursuing cosmetic facial surgery. Chin deformities are the most common abnormality of the facial bones, with microgenia being the most common abnormality but with the lack of an associated functional deficit, microgenia often remains untreated. Most commonly, patients present requesting rhinoplasty and are unaware of their associated chin deficit.

When a patient is considered for chin augmentation with an alloplastic implant, it is important to carefully select the proper implant size and shape. Some alloplastic chin implants, particularly silicone, will heal with the formation of a fibrous capsule resulting in thickening of the overlying skin and soft tissues. This should be taken into account when calculating the size of the augmentation. Women are most judiciously treated with under correction, to avoid the necessity of removal of an implant that is perceived as too large. This is rarely the case in male patients, where a strong chin is viewed as a positive facial feature [4].

Severe microgenia is a contraindication to augmentation mentoplasty. Other contraindications include labial incompetence, lip protrusion, shortened mandibular height, severe malocclusion, and periodontal disease.

As with all procedures in facial plastic surgery, thoughtful preoperative analysis is crucial to a successful outcome. This analysis involves careful threedimensional evaluation of the face as a whole, with specific attention directed toward the chin, lips, and nose [5]. The patient is examined from all angles, accompanied by precise photo documentation in the standard views. Face shape and length and the relationship of the chin and nose to the face are examined. The chin is analyzed for its soft tissue components and its bony structure. Chin projection and width are noted as is the position and depth of the labiomental fold. Labial competence and lip position