Advances in Cutaneous Aesthetic Surgery

THE PHYSICAL APPEARANCE of aged skin derives from a combination of intrinsic and extrinsic factors. Intrinsic changes are largely genetically determined and include the effects of gravity (sagging), expression lines, and atrophy of the dermis and subcutaneous tissue. Extrinsic aging is related to environmental influences with sunlight being the most important, followed by smoking and chemical exposure. The effects of long-term sun exposure on skin (photoaging) are characterized by a recognizable progression of textural, vascular, and pigmentary changes. Dyschromia, lentigines (brown macules), and telangiectasias appear gradually, and the skin loses its tautness and smoothness and develops fine and coarse rhytides (wrinkles), keratoses, and, possibly, skin cancers. The aesthetic relationships of the aged face are also altered by a decrease in the volume of the facial skeleton, loss of suspension of overlying structures, and reconforming of the skin in folds and creases, especially around the orifices. Eyelid skin redundancy and herniation of orbital fat pads create eyelid "bags" that are accentuated by brow ptosis. In addition, sagging of the chin and neck occur and are enhanced by buccal fat pad atrophy and downward angulation of the oral commissures. Medical and surgical treatments are available to help reverse these changes by improving irregularities of the skin surface, relaxing expression lines, filling cutaneous defects, and removing excess fat or skin.

Fine wrinkles and mild textural changes of aged skin can be improved by topical therapy with retinoids and, possibly, other topical agents, including ascorbic acid, α-hydroxy acids (glycolic and lactic acids), and β-hydroxy acids (salicylic acid). Skin resurfacing with conventional methods, such as chemical peels and dermabrasion, has been revolutionized by advances in laser techniques for the treatment of more severe or diffuse wrinkling and photodamage and of scars caused by acne, chickenpox, surgery, or trauma. High-energy short-pulsed or scanned CO₂ lasers emitting light at 10600 nm achieve effective depth-controlled tissue removal in a relatively bloodless manner, while limiting the conduction of heat to the surrounding normal structures and reducing the risk of scarring. This technique may be used for the treatment of patients of any age with mild, moderate, or severe wrinkling. Theoretically, intervention at an earlier stage of wrinkling will halt the progression of photodamage. However, aesthetic improvement is usually more apparent in patients with more severe wrinkling.¹ The ideal candidates for laser resurfacing are patients with wrinkles at rest and limited sagging. Wrinkles in the periorbital and perioral areas, traditionally unresponsive to face-lift procedures (rhytidectomy), and wrinkles on the medial lower and lateral cheeks respond very favorably to laser therapy. Patients with moderate to severe sagging and wrinkling often benefit from both rhytidectomy and laser resurfacing.

The marked improvement in the appearance of photoaged skin after CO₂ resurfacing has been related to 3 tissue effects: complete vaporization of the photodamaged epidermis and superficial dermis, shrinkage of collagen fibers by thermal denaturation, and wound remodeling with production of new collagen during the healing phase.² Several studies have shown 50% to 90% improvement in the appearance of photodamaged skin after laser resurfacing based on photographic assessments or quantitative analyses of wrinkle depth.^{3 - 4} Because the technique of CO₂ laser resurfacing is relatively new, there are no long-term studies to determine the long-lasting efficacy of the procedure.

The adverse effects of laser resurfacing include edema, oozing, and crusting, which develop shortly after the procedure and last from 7 to 14 days. Erythema also occurs and may persist for 6 to 12 weeks.³ Postoperative complications occur infrequently and include pigmentary changes, persistent erythema, infection, and, rarely, scarring.⁵

The pulsed erbium:yttrium-aluminum-garnet (Er:YAG) laser has been introduced to improve the adverse effect profile of the CO₂ laser. The Er:YAG laser emits infrared light at 2940 nm, which is much better absorbed by tissue water. It achieves finer superficial tissue ablation with less residual thermal damage and faster resolution of initial postoperative oozing and crusting (approximately 1 week vs 2 weeks) compared with CO₂ laser resurfacing. The Er:YAG laser is effective for treating superficial photodamage but not moderate or severe wrinkling, presumably because of the absence of a thermal effect on collagen fibers. Early studies suggest that the limited thermal injury induced by the Er:YAG laser may allow resurfacing of photaged skin on the neck and dorsal hands, areas traditionally avoided in CO₂ laser resurfacing because of the associated high risk of scarring.⁶ Efforts are currently being focused on skin resurfacing with infrared light–emitting lasers and concomitant cooling of the epidermis to induce tightening of wrinkled skin without a visible wound (subsurface resurfacing).⁷

Dynamic creases that appear with facial expression, such as frown lines, forehead lines, and crow's feet, are more resistant to laser resurfacing and respond better to treatment with botulinum A exotoxin, a neurotoxin produced by Clostridium botulinum. Botulinum toxin has been used in very dilute forms to treat a variety of dystonic disorders, but it has not yet been approved by the Food and Drug Administration (FDA) for cosmetic use. To correct glabellar wrinkles, the toxin is injected into the procerus and corrugator muscles; to correct horizontal frown lines, into the frontalis muscle; and to correct lateral canthal creases, into the orbicularis muscle. The toxin binds irreversibly to the presynaptic membrane receptors at the neuromuscular junction of striated muscle fibers and inhibits the release of acetylcholine. This inhibitory effect is permanent in all exposed neuromuscular junctions, but the formation of axonal sprouts and new motor end plates gradually restores muscle function.⁸ The paralyzing effect is noticed 1 to 3 days after injection and lasts 3 to 4 months on average with increasing duration after several treatments. Although treatment resistance has been seen in patients with dystonia because of production of botulinum toxin–blocking IgG antibodies,⁹ treatment resistance has not been reported with cosmetic use, presumably because of lower doses of injected toxin or less frequent treatments. Contraindications to botulinum toxin treatment include pregnancy, history of neuromuscular disease, and known sensitivity to the toxin or to human albumin, which is contained in the toxin solution. The most serious complications of botulinum toxin injections are eyelid ptosis and diplopia, which occur in 1% to 2% of treatment sessions and usually resolve completely in 2 to 3 weeks.⁸ Mild adverse effects, such as pain from the injections, headaches, and bruising, are temporary.

The development of safe, injectable filling materials for permanent correction of soft tissue losses from aging has been limited by host responses to augmentation materials that impair their long-term survival. Bovine dermal collagen implants, approved by the FDA, have been used extensively since the early 1980s for the correction of wrinkles and depressed scars. They consist of sterile, purified, reconstituted fibrillar bovine collagen (types I and III) and are mainly used to soften nasolabial, melolabial, and perioral wrinkles, augment lip lines, or improve soft, shallow, distensible scars related to acne or trauma. The major drawback of bovine collagen is its rapid degradation by human collagenases, resulting in loss of clinical effect within 3 to 6 months after injection. Because 1% to 3% of the general population are allergic to bovine collagen, intradermal testing is necessary prior to injection.¹⁰

A variety of autologous collagen products have been developed recently and used experimentally as facial implants with the prospect of a longer duration of correction and absence of allergic reactions. Autologous collagen is produced in vitro by cultured dermal fibroblasts from skin biopsy specimens (Isolagen Technologies, Paramus, NJ) or is extracted from excised skin obtained from other procedures, such as face lifts, abdominoplasties, or blepharoplasties (Autologen, Collagenesis Inc, Beverly, Mass). Although clinical results are difficult to predict, a preliminary study using collagen from cultured dermal fibroblasts showed clinical improvement of facial rhytides in only 2 of 12 patients at 6 months after injection.¹¹ The safety and efficacy of these procedures remain to be determined.

The use of autologous fat transplantation for soft tissue augmentation has increased since the development of liposuction for harvesting viable adipose tissue. Because of its soft consistency, autologous fat is used to correct deep subcutaneous tissue losses that occur with aging or to elevate depressed facial scars. The longevity of fat transplants depends on several parameters, including the harvesting and grafting technique, the quality of transplanted tissue, and the vascularity of the recipient site. While some investigators have reported a long-lasting effect, most studies show a gradual absorption of the transplanted fat with a 40% to 60% graft survival rate 1 year after injection.¹² Serial injections may provide the most satisfactory and long-lasting results.

Injectable cross-linked hyaluronic acid is another promising augmentation material. Being a natural component of the ground substance of the dermis and identical across species, it has very low immunogenicity and also provides a hydrating effect. In 1 study the degree of correction or the aesthetic improvement following injection with hyaluronic acid declined from 98% at 2 weeks after the procedure to 66% at 1 year after injection.¹³ Although the longevity of the correction may be limited, the absence of allergic reactions gives hyaluronic acid an important advantage over bovine collagen.

Synthetic filling agents, such as expanded polytetrafluoroethylene (ePTFE [Gore-Tex, W. L. Gore & Associates, Elkton, Md; SoftForm, Collagen Co, Palo Alto, Calif]), have also been used. ePTFE is a synthetic biomaterial used for deep wrinkles and furrows, particularly for correction of the nasolabial fold and enhancement of the vermilion border of the lip. Manufactured as sutures, tubes, rolls, and patches of various dimensions, ePTFE can be cut to fit the size of the soft tissue defect. After local anesthesia, the implant is positioned by direct tunneling under the defect, producing a permanent, yet removable filling effect. Since the material is inert, it does not cause allergic reactions, but foreign body reactions and incorrect positioning have been reported.¹⁴

With aging, some patients have increased fat deposition in the cheeks and the submental and submandibular areas. Cervicofacial liposuction, used either alone or in conjunction with rhytidectomy, has become an effective technique for removing fat from these areas and for improving the contour of the neck and face.¹⁵ The development of the tumescent anesthetic technique has transformed the practice of liposuction into an outpatient treatment with minimal adverse effects.¹⁶ This approach involves injecting large volumes (0.2-6 L) of dilute lidocaine, epinephrine, and sodium bicarbonate into the subcutaneous fat prior to liposuction. The relatively avascular nature of the subcutaneous tissue in conjunction with the vasoconstriction produced by the epinephrine and the compression of the vasculature by the infused volume allows for the safe use of large concentrations of lidocaine (55 mg/kg). Tumescent anesthesia limits blood loss during the procedure and has virtually eliminated the need for general anesthesia and intravenous fluid replacement. It reduces the postoperative pain, swelling, inflammation, and bruising of the skin compared with liposuction performed with general anesthesia.¹⁶ Another liposuction technique uses ultrasound waves to liquefy fat, which is then suctioned by standard liposuction tubes. Although ultrasound-assisted liposuction is effective for the treatment of fibrous areas, such as the back and buttocks, and for gynecomastia, its efficacy and adverse effect profile compared with standard liposuction remain controversial.¹⁷