Chapter 80. Facial Fillers & Implants

Essentials of Diagnosis

• Analysis of the type of rhytid, including anatomic location and depth and whether it is static or dynamic
• Knowledge of the longevity of each facial injectable
• Analysis of facial skeletal proportion, occlusion, and preoperative symmetry.

General Considerations

Facial contouring is a recent trend in facial aesthetic surgery. Facial implants serve to add volume, providing a more appealing shape to a person's face. Facial injectables have reached tremendous popularity due to their safety, “no-down-time” appeal, and economics. Both are discussed to provide background on an exhaustive topic.

There are a large variety of facial injectables, each serving a different purpose. A brief summary of the most commonly used facial injectables with a delineation of their advantages and disadvantages will be highlighted.

Botulinum Toxin

Botulinum toxin A (BOTOX® [Allergan, Irvine, CA] and Dysport [Medicis, Scottsdale, AZ]) decreases facial lines and wrinkles at sites of skin pleating caused by hyperfunctioning mimetic muscles. Botulinum toxin A is FDA approved for treatment of the glabella. Off-label uses have included periorbital lines (crow's feet) platysmal bands, the forehead, and nasolabial and melolabial lines. Botulinum toxin A is also used for hyperhydrosis of the palms and armpits.

Botulinum toxin A causes paralysis by inhibiting acetylcholine release at the neuromuscular junction. This is accomplished in three steps. First, the toxin binds the nerve. Second, the toxin is internalized into the nerve. Third, the toxin is cleaved by internal proteolytic enzymes, and the degradation by-products interfere with the normal process of vesicle fusion to the plasma membrane. This results in the inhibition of the exocytosis of acetylcholine.

The toxin requires 24–72 hours to take effect, reflecting the time necessary to disrupt the synaptosomal process. In very rare circumstances, some individuals require as many as 5 days for the full effect to be observed. The effects of botulinum toxin last from 2 to 6 months.

The dose of the toxin is measured as one standard unit, which is equal to the amount necessary to kill 50% of Swiss–Webster mice injected with that dose. Extrapolating the data from mouse experimentation, Meyer and Eddie estimated that a 104 kg adult male would sustain a lethal dose of botulinum toxin type A at amounts exceeding 3500 units, a dose that far surpasses any dosing regimen in the cosmetic treatment of the aging face.

Botulinum toxin is contraindicated in patients with peripheral motor neuropathic diseases or neuromuscular functional disorders such as Eaton–Lambert syndrome and myasthenia gravis. Similarly, botulinum toxin type A is contraindicated in pregnant patients and those who are lactating, although unintentional administration has not resulted in birth defects or pregnancy issues. Finally, caution should be taken when injecting botulinum toxin type A to those taking aminoglycoside antibiotics or other agents that interfere with neuromuscular transmission, since these agents may potentiate the effects of botulinum toxin both locally and regionally.

Hyaluronic Acid Derivatives

Hyaluronic acid derivatives (Restylane [Medicis Aesthetics, Scottsdale, AZ], Captique [Allergan, Irvine, CA] Juvederm [Allergan, Irvine, CA]) are glycosaminoglycan biopolymers, similar to the substance found in the intercellular layers of the dermis of the skin, and are very biocompatible. They are used primarily for lip and nasolabial fold augmentation and for fine wrinkles. Some recent uses of hyaluronic acid derivatives include nonsurgical rhinoplasty and volumetric filling in senile earlobe repair. Rare cases of hypersensitivity have been reported, but preinjection skin testing is generally not advocated. Volume enhancement with hyaluronic acid derivatives lasts 4–6 months, with some reports of material lasting for up to 16 months. Newer formulations of hyaluronic acid containing preincorporated 3% lidocaine have been shown to have equivalent product longevity.

Complications are relatively uncommon with hyaluronic acid derivatives. In cases of overaugmentation, hyaluronidase can be used to decrease the amount of dermal filling. Caution should be taken when injecting superior to the Frankfort horizontal line. Peter describes a case of retinal artery occlusion through retrograde flow through a peripheral branch of the ophthalmic artery. Skin necrosis is rare (a report of two cases of 400,000).

Poly-l-Lactic Acid

Poly-l-lactic acid (Sculptra) is a volumetric filler currently FDA approved for the treatment of lipoatrophy in HIV patients. Lipoatrophy in HIV is due to a number of factors including reverse transcriptase inhibitors and the disease process itself. Recently, poly-l-lactic acid has been used in an off-label capacity as a non-HIV facial filler. The main complication is nodule formation. This can be avoided by injecting deep to subcutaneous tissues and not in areas of significant muscle motion such as the lips. The duration of augmentation with poly-l-lactic acid is up to 3 years.

Calcium Hydroxylapatite

Calcium hydroxylapatite (Radiance FN, Bioform, Inc, Franksville, WI) is a major mineral constituent of bone. It has an off-label use for soft tissue augmentation in the face, primarily for reduction of nasolabial folds. Calcium hydroxylapatite should be injected subdermally to avoid nodule formation. In addition, the injection of radiesse should be avoided in the lips. The true longevity of calcium hydroxylapatite is not known.

Bovine Collagen

Bovine collagen (Zyderm and Zyplast; McGhan Medical Corporation, Fremont, CA) is composed of 95% type I collagen and is most commonly used to augment lips and nasolabial folds. Zyplast is cross-linked with glutaraldehyde (creates a longer lasting effect) but must be injected into the deep dermis. Zyderm is injected into the superficial dermis. Hypersensitivity reactions occur in about 3% of patients; therefore, skin testing and even secondary skin testing are advocated. Bovine collagen augmentation lasts 2–4 months.

Human-Derived Collagen

Human-derived collagen (Cosmoderm and Cosmoplast, Inamed Corporation, Santa Barbara, CA) is used for the treatment of facial rhytids and lip augmentation. In contrast to bovine-derived collagen, human-derived collagen carries essentially no risk of hypersensitivity reactions, obviating the necessity for pretreatment skin testing. Typically, injections maintain augmentation similar to that of bovine collagen. Adverse reactions may occur in patients with known allergy to bovine collagen.

Autologous Fat

Fat transplantation has the advantage of being an autologous substance. Fat transplantation is used as a volumetric filler. The concept of loss of facial volume is recent, and surgeons recontour the face, the nasolabial folds, temporal fossa, prejowl sulcus, and perioral and periorbital areas.

Most commonly, fat is harvested from the lateral thigh or abdominal region. Fat is then either strained or centrifuged, and injected into areas requiring volume. Technique in handling fat is crucial in maintaining adipocyte viability. Fat transplantation often requires multiple treatment sessions and has variable degrees of resorption. Fat can be frozen with minimal loss in fat viability and reinjected at a future date.

Disadvantages of fat harvest include donor site morbidity, potential for prolonged facial swelling, and unpredictable resorption. In addition, fat can lead to granulomas that can be treated with triamcinolone injections or direct excision. Advantages of fat transplantation include a potentially permanent natural facial filler that can serve as an adjunctive or stand-alone procedure.

Preoperative Assessment

The hypoplastic chin is the most common indication for chin augmentation. On frontal view, the face can be divided into thirds, with the lower third spanning from the subnasale to the mentum. Aging results in loss of vertical height of the mandible. On lateral view, a vertical line can be dropped from the lower lip. In females, the chin should be 1–2 mm posterior to this line. In males, the chin should lie at the same level as this line. There are a number of techniques to analyze chin size and projection (Table 80–1).

Patients' occlusion should be assessed preoperatively to ensure that orthognathic treatment is not necessary. Type I occlusion is when the mesial–buccal cusp of the maxillary first molar contacts with the mandibular first molar's buccal groove. Type II occlusion is when the maxillary first molar is anterior to the buccal groove (an overbite), and Type III is when the maxillary molar is posterior (an underbite).

Analysis of the malar and submalar region is much more complex and requires three-dimensional planning. The submalar triangle is the area below the malar eminence and the location of many facial deficiencies. Binder classified patterns of midfacial deformity and the resultant augmentation required. There are a variety of methods of analyzing the midface and its projection (Table 80–2).

Procedure

Chin implantation can take place by an external or intraoral route. The extraoral approach has the advantage of not contaminating the implant through the oral cavity. The intraoral approach prevents an external scar. Implants placed intraorally tend to “ride” high postoperatively, partly because of the difficulty in fixating the implant. The surgeon should be aware of the position of the mental nerve, which emanates from the bone approximately 1 cm above the edge of the mandible and approximately 2.5–3.5 cm from the midline, lying in the vertical plane between the first and second premolar.

Typically, malar and submalar implants are placed by an intraoral route. An incision is made along the upper gingivobuccal sulcus, and an elevator is used to lift the periosteum off the face of the maxilla. The masseteric fibers are released off the face of the maxilla.

The infraorbital nerve is avoided as it exits the infraorbital foramen 4–7 mm below the inferior orbital rim on a vertical line that descends from the medial limbus of the iris. A tight periosteal pocket is created that is small enough to fit the implant tightly. The implant can be further fixated with a titanium screw, a resorbable suture, or a temporary external suture and bolster.

Complications

Complications of facial implants are rare and include hematoma, infection, nerve paresthesia (transient or permanent), and motor nerve injury. No study has shown a change in infection rates in extraoral versus intraoral approaches.

ePTFE (W.L. Gore & Associates, Flagstaff, AZ) is an expanded, strongly hydrophobic, fibrillated polymer that can be produced in sheets, three-dimensional strands, and suture material. ePTFE has been associated with infection, extrusion, and scarring. It has been used with success in a recent study with only 0.62% of implants requiring removal for infection. ePTFE has the advantage of being soft, with minimal encapsulation and bony resorption. ePTFE is unavailable at this time as a preformed facial implant.

Silicone is a relatively inert substance, which has more encapsulation than ePTFE. Bony resorption increases with overlying muscle action translating to implant mobility. Therefore, the implant should be secured in a tight pocket with either sutures or titanium screws. In addition, subperiosteal placement increases bony resorption. Well-positioned implants with osseous erosion should not be replaced. Silicone implants are easier to place than ePTFE owing to less flexibility at the peripheral portion of the implant and higher resistance to crushing.

Malar and submalar implants can result in injury to sensory nerve (V2) or motor nerve (buccal or temporal branch), albeit a rare event. More commonly, midface implants may result in asymmetry due to preexisting facial skeleton imbalances.