Pathophysiologic factors in aging associated with the need for facial implants

It is generally accepted that patients endowed with strong, well-balanced skeletal characteristics better withstand the ravages of age. Analysis of the faces of young people reveals an abundance of soft tissues, which are the basis for the harmonious structure of the youthful face. Its main characteristics are full cheeks and soft, symmetrical contours without sharp, uneven protrusions, indentations or wrinkles, and without skin color disorders. The structures of the face, like the rest of the body, are constantly changing and are affected by many factors (insolation, weight change, injury or disease). Even physical exercise contributes to the formation of certain persistent and identifiable defects in the facial contour. The development of lines and wrinkles is the result of hereditary factors, insolation and other environmental influences, smoking, concomitant diseases, gravity and muscle contractions.

Depending on the underlying skeletal structures, the involutional changes in the soft tissues associated with the aging process produce different but characteristic facial contours that become increasingly obvious and pronounced with time. Identification of these various defects and configurations caused by aging is an integral part of successful corrective interventions. Such changes include the development of a general flattening of the midface, thinning of the vermilion border of the lips, sagging of the cheeks, formation of areas of deep depressions in the cheeks, deep folds of the skin and wrinkles. Other specific changes in the soft tissues include increased expression of the nasolabial folds, flattening of the soft tissue component of the chin and formation of anterior cheek groove.

Among the many techniques used in facial rejuvenation surgery, the ability to permanently replace soft tissue volume in sufficient quantity and with a lasting effect is still lacking. The new popularity of fat grafting has led to a re-evaluation of tissue replacement as a key point in the rejuvenation process. However, if autofat is not available, in the presence of facial soft tissue atrophy that cannot be corrected by repositioning, the choice is limited to replacement with allografts. Alloplastic volume replacement techniques can solve these problems by smoothing out sharp angles or depressions, lifting underlying surfaces to smooth out wrinkles, and correcting inadequate skeletal structures.

Surgical approaches to nose augmentation

The relatively thin skin on the bridge of the nose often cannot provide sufficient concealment of poorly contoured replacement tissues. Nasal augmentation is performed using various materials. Currently, the most commonly used implants are made of silicone, ePTFE, and polyethylene. Silicone causes minor atrophy of the overlying skin over time and must be fixed to prevent displacement. Both ePTFE and silicone can cause infection, but implants made of these materials are easily removed and replaced. Polyethylene (Medpore) implants, like any other that allows significant tissue ingrowth, can be removed only if there is significant damage to the surrounding tissue. Homocartilage has a high resorption rate, and autogenous bone can become deformed.

Since human hyaline cartilage has a limited capacity for regeneration, effective long-term reconstruction of the nose remains problematic despite ongoing efforts using various autografts, allografts, and alloplastic materials. A suitable replacement implant designed to reconstruct the original nasal profile must have a number of unique characteristics. It must be of adequate length and have consistent curvature, thickness, and tapered edges so that it fits well over the bridge of the nose and has a smooth transition into the surrounding soft tissue and bone. In addition, it must be pliable and flexible to withstand stress and trauma over the long term.

The use of autologous tissue eliminates the problem of biocompatibility, but sometimes fails to provide sufficient volume to restore shape and size. A more suitable substitute for the missing skeletal structure, especially in the nasal dorsum, may be a graft of new cartilage obtained from autologous cells, which closely mimics the original skeletal contour. Such cartilage implants are synthesized using tissue engineering. The concept is to use donor septal cartilage tissue, which is harvested and separated into its cellular components. The cells are cultured in vitro. By pressing, a synthetic alginate scaffold is created in the shape of an M-graft for the nasal dorsum. The cells are introduced into a gelatin scaffold, which is implanted under the skin of a mouse, where they are allowed to develop, in vivo, to their final shape. During this period, the alginate scaffold is gradually resorbed and replaced by viable hyaline cartilage. The cartilage is then harvested as an autograft. This technology promises to be a good addition to current capabilities for volume restoration on the nose and face in the near future (personal communication, G. Tobias, 1999).

Surgical approaches to correction of the middle third of the face

Advances in midface aesthetics and lifts have raised patient expectations. Our ability to rejuvenate the midface and address volume loss in this area has increased dramatically. Rhytidectomy has become just one component of facial rejuvenation. Brow lifts, volume-replenishing procedures, cheek lifts, midface lifts, and resurfacing and peeling techniques must now be considered when developing a surgical plan. Whenever possible, the goal of midface enhancement is to combine the two key components of rejuvenation and augmentation. If either surgical option alone fails to reposition sagging soft tissue or replace volume loss, an alternative approach should be individually combined with other modalities to provide the most comprehensive approach to the problem. Specific criteria exist to identify areas of aesthetic deficiency and to correct them with allografts. In addition, other features of aging and midface imbalances must be identified. These are signs of aging around the eye sockets, drooping and loss of volume in the midface, as well as developmental deficiencies in the facial bone structure, accompanied by soft tissue imbalance, ptosis and asymmetry.

Aging around the orbits. With age, the orbital septum weakens and orbital fat protrudes, causing bags under the eyes. The orbicularis oculi muscle droops, especially at its lowest point. Conventional blepharoplasty can worsen the stretching of the inferior canthal ligament, causing a trough-shaped deformity or, in severe cases, senile ectropion. Aging is accompanied by atrophy of the subcutaneous tissue, which is most pronounced in the very thin infraorbital skin, giving the eyes a sunken appearance.

Skeletal insufficiency and imbalance usually have their origin in hypoplasia and expected imbalance of the facial skeleton, which is aggravated by the aging process.

Midface drooping and volume loss. Midface drooping involves the ptosis of the subcutaneous tissues below the orbit, the malar fat pad, the fat under the orbicularis oculi, and the orbicularis oculi itself. As the cheek droops and rolls over the top of the nasolabial fold, the thicker tissues of the malar fat pad also move downward, leaving the infraorbital area with a thin soft tissue covering. Thus, the nasozygomatic area begins to protrude, the inferior orbit appears empty, and the inferior orbital rim is contoured. Subcutaneous tissue loss occurs throughout the body, but affects the midface most, including the buccal fat pad, malar fat pad, and fat under the orbicularis oculi. As volume loss and drooping occurs, the infraorbital area and cheek begin to show signs of aging.

In the midface, the greatest tissue deficit is found in the space described as the "subzygomatic triangle." This inverted-triangle-shaped area is bounded superiorly by the malar eminence, medially by the nasolabial fold, and laterally by the body of the masseter muscle. In patients with severe degenerative changes in the skin, loss of underlying fat, and deficiency of underlying bone structures, the gravitational effects of aging are exacerbated and cause further deepening or sinking, folds, and wrinkles. In patients with particularly prominent cheekbones and a deficiency of subcutaneous or deep fat, the facial depressions will be further accentuated. These changes give healthy faces a gloomy or haggard appearance. A severe form of this degeneration may be seen in anorexia nervosa, starvation, or in the newly identified group of HIV-positive patients receiving proteolytic enzyme inhibitors for long periods. In combination with the underlying disease, protease inhibitors and other new generation AIDS drugs result in the destruction of midface and buccal fat. This condition of soft tissue volume loss, also associated with the aging process, often precludes rhytidectomy alone as a rejuvenation procedure and is now successfully treated with computer-designed, custom implants.

Midface Surgery: A Multimodal, "Multi-Level" Approach

For successful facial rejuvenation, tissue drooping and volume loss must be concealed, corrected, or replaced. In today’s environment, this requires a multi-level and multi-modal approach to the pathophysiological mechanisms of aging. Concealing techniques such as marginal arch blepharoplasty blunt the nasozygomatic groove by fixing infraorbital fat behind the marginal arch. Mid-level cheek lift techniques correct midface drooping by lifting the tissues in this area and fixing them in a more superolateral direction. Alloplastic or autogenous augmentation techniques correct the effects of midface drooping by replacing tissue volume and providing soft tissue support from deep within. Since there are many elements of structural deficiency and aging, laser resurfacing and many other adjunctive techniques are used along with rhytidectomy, as well as facial implants as a necessary part of restoring and achieving the aesthetic qualities of a youthful face. Deficiencies related to the superficial, soft tissue component of the face, be it the epidermis, dermis, subcutaneous fat or, in some cases, muscle, are corrected using autologous tissues and synthetic implants. Autologous fat, homotransplants and xenotransplants such as AlloDerm (Life Cell, USA) and collagen, as well as alloplastic materials such as ePTFE are only a small part of the materials used. The significant number of soft tissue fillers available on the world market today indicates that the ideal substitute for facial soft tissue components has not yet been found.

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