Nonoperative Facial Rejuvenation

Formulations

To date, the FDA has approved three distinct formulations of BoNT-A for both therapeutic and cosmetic purposes, and one formulation of BoNT-B for therapeutic use only. The original formulation of BoNT-A, onabotulinumtoxin-A (BOTOX/BOTOX Cosmetic/Vistabel/vistabex; Allergan, CA, USA), has been joined by abobotulinumtoxin-A (Dysport or Azzalure; Galderma, TX, USA), and icobotulinumtoxin-A (Xeomin/NT-201; Merz Pharma GmBH & Co., Frankfurt, Germany). Only one formulation of BoNT-B-rimabotulinumtoxinB (Myobloc/Neurobloc; Solstice Neurosciences, CA, USA) is available in North America. All products differ in their pharmokinetics and therefore clinical doses vary and are not interchangeable.

Cosmetic Uses of BoNT-A

Initially approved only for injection into the glabellar rhytids, BoNT now is used for dozens of off-label applications on the face ( Fig. 61.1 ). These include controlled paresis of hyperkinetic lines of the face and neck, elevation of various facial subunits by altering muscle equilibrium between depressor and elevator muscles, and reestablishing facial symmetry by selective blockade of muscles of facial expression. BoNT is also increasingly used perioperatively to help with scar management or to stabilize brow position following brow elevation.

A number of technical factors can contribute to a comfortable and more predictable experience:

• Topical anesthetic is applied 30 minutes prior to the procedure (the authors prefer a triple anesthetic preparation of lidocaine, tetracaine, and benzocaine).

• Ice or cold compresses is applied immediately prior to injection.

• If a marker is used, we prefer removable white ink markers (Viscot, NJ).

• A 32G (or 33G) short needle is used on a hubless 0.5 syringe. Larger syringes provide less tactile feedback to the injector and can be more uncomfortable to patients.

• The depth of penetration of the needle follows the esthetic goals and specific muscle anatomy. When injecting the corrugators, for instance, the depth of penetration is more superficial laterally and becomes deeper medially.

• Injection is always made with low pressure and in small aliquots. It is preferable to inject multiple times than to inject a large quantity of fluid in a single push.

• It is preferable to distribute the toxin across several syringes in order to maintain tip sharpness and thus diminish patient discomfort.

• Where a large quantity of toxin is required (e.g., in men with a heavy corrugator complex), it may be preferable to increase the concentration of the toxin to diminish diffusion. In most instances with BoNT, the authors create a 2-mL solution of 5 u/0.1 mL for routine cases and 10 u/0.1 mL for cases where a higher concentration is required.

• Not all toxins have the same clinical characteristics. Abobotulinumtoxin-A for instance appears to have a wider diffusion circle. This can be advantageous in the forehead where multiple entries are often required to achieve meaningful reduction of rhytides. On the other hand, where targeting a specific muscle, highly concentrated onabotulinumtoxin-A may yield more reliable results.

• The areas injected are carefully mapped and the patient is seen between 7 and 14 days following injection for follow-up.

Adverse Effects and Complications

While adverse effects of BoNT are rare, they include watery, dry or crossed eyes. It may also include an incompetent mouth, the inability to whistle, dysphagia, and neck weakness. Most dissatisfaction from BoNT stems from unexpected changes in facial appearance or expression. Common complaints in include:

• Ptosis of the eyelid from injection into the forehead or corrugator complex.

• Ptosis of the brow from forehead injection.

• Overarching eyebrows from injection of the corrugator complex.

• Lower lid festoon formation from injection of crow’s feet and secondary loss of orbicularis tone.

• Changes in phonation or smile from perioral injection.

While these adverse effects are not entirely avoidable, they could be minimized by gaining better knowledge of the underlying facial anatomy and physiology as well as paying close attention to individual anatomic variability.

Historic Context

The era of absorbable dermal fillers was ushered in in the latter part of the 20th century with the introduction of collagen fillers. Initially made of bovine collagen, fillers based on human collagen became popular in the late 1990s. Products such as Zyderm and Zyplast that were animal-derived collagen required prior skin testing, with hypersensitivity reactions observed in as much as 10% of patients. In 2003 the US Food and Drug Administration approved the use of Restylane (Galderma), a hyaluronic-based product as a class III device to treat facial rhytids. Dozens of products have since been introduced to address a variety of facial volumetric needs.

Rheological Properties

Rheology refers to the physics of deformation and flow of materials, typically in a state between solid and liquid. An understanding of rheological properties of various injectable fillers is critical to the appreciation of their clinical behavior. G′ or elastic modulus refers to the resistance of the material to an applied strain and is commonly used as a measure of hardness or softness of a given material. G′′, or the viscous modulus, refers to the energy dissipation due to friction. Other valuable measurements include resistance to compression and maximum water uptake. These properties, when combined with experimental data from human or animal models, provide valuable insight with regard to the actual in vivo behavior of various materials. It is important to note that physical properties of the filler may not always correlate with their performance in the face over time.

Nonbiodegradable Fillers