Alloplasts in Nasal Surgery

History

At its most basic level, rhinoplasty is an alteration in the form and function of the nose by removal, modification, or augmentation of existing nasal structures. Historically, nasal mutilation was inflicted with the intention of leaving a visible marker of a degraded social status for thieves, adulterers, and military or political prisoners. The syphilis epidemic in Western Europe in the sixteenth and seventheenth centuries caused a significant number of saddle nose deformities and left victims with conspicuous sequelae of sexual promiscuity. Military wounds also left victims with nasal deformities requiring treatment.

The simplest form of augmentation is the prosthesis. Justinian II (“Rhinotmesis”), a Byzantine emperor whose nose was amputated after he was deposed (nasal and facial deformities precluded individuals from ruling), wore a nasal prosthesis when he reclaimed his throne. Tycho Brahe, the Danish astronomer, wore a silver prosthesis to camouflage a nasal deformity.

Soft tissue reconstruction of the nose with forehead or cheek skin flaps dates from as early as the sixth century bc in India, and forearm pedicled flap repair was well known in Italy prior to Tagiacozzi's publication in the sixteenth century. These early surgical interventions in the preanesthetic era were intended to replace large amounts of nasal volume and skin coverage. More focused reconstruction of nasal deformities—in particular, the saddle nose deformity—began in earnest in the late nineteenth to early twentieth centuries, as modern anesthetic techniques and antisepsis were introduced. While subtler than the earlier treatment of more dramatic nasal amputations, the repair of these injuries was primarily aimed at restoration of nasal volume and skin coverage. Some of the materials used, including stones from the Black Sea, duck breastbone, pearls, and ivory, may seem inexact and perhaps more than a little odd, but the deformities being treated were severe and even modest improvements were appreciated. At best, the materials may have been well-tolerated foreign bodies with fibrous encapsulation, but it seems obvious they were chosen more for their physical qualities than for their biocompatibility.

The development of synthetic polymers in the mid to late twentieth century led to the greatest increase in the use of nasal implants. In particular, solid silicone implants were introduced and are still in use today. These were designed primarily for dorsal augmentation but some later designs incorporated struts for columellar and tip support. These implants are fairly well tolerated, but implant infections and extrusions have been reported and will be discussed later in this chapter. Other implants have also been developed over the past two decades for isolated columellar support, premaxillary augmentation, and nasal valve support; their use will also be covered in this chapter.

Anatomy

Five main areas can typically be considered for alloplastic nasal augmentation: the dorsum, premaxilla, nasal valve, ala, and columella. Additionally, some implants will include aspects designed to augment the nasal tip. Congenitally shallow nasal dorsal profiles often seen in Asian and African American patients are amenable to dorsal onlay implants. In patients with limited or weak tip projection and support, a single-piece implant can be used to both augment dorsal height and to provide tip support. A retruse premaxilla can be augmented with an implant to restore proper balance to the lower third of the nose. Recently, new implants have been introduced to modify/support the internal nasal valve without adding excessive bulk. Implants can be added to the nasal ala to correct alar contour, while implants placed in the columella can aid in augmenting tip projection, altering tip rotation or reshaping the columella itself. In general, space-occupying implants are better tolerated than those that provide structural support; there are exceptions to this rule, and factors such as the health and vascularity of the local soft tissues, implant stabilization, and the physical and chemical characteristics of the implant itself will also have a significant impact on implant success.

Alternatives

Traditional teaching of rhinoplasty techniques dictates the use of autologous materials whenever possible. Autologous septal, conchal, and costal cartilage are the most commonly used material for nasal grafting. They are readily harvestable, have minimal donor site morbidity, can generally provide sufficient volume of cartilage, are relatively easy to carve, and provide fairly predictable results. Alternatively, outer table calvarial or iliac crest bone grafts can be used, but due to their rigidity, they are only practical for dorsal onlay (and columellar support) grafts. Temporalis fascia can be used to soften graft edges but provides neither volume augmentation nor support. Erol and colleagues described the use of the “Turkish Delight” graft: minced cartilage is mixed with autologous blood and wrapped in oxidized cellulose. The subsequent fibrotic response provides bulk augmentation for the nasal dorsum but cannot be used in structural settings.

Homografts, such as irradiated rib cartilage (IRC), can be considered as an alternative if autologous tissue is unavailable or insufficient or the patient refuses a second surgical incision. IRC is harvested from human cadavers and processed to reduce the potential for infection transmission or immunologic host rejection. It has been in use for over 20 years and the literature is mixed as to the ultimate fate of irradiated cartilage. Schuller et al. initially described good results using IRC. However, subsequent long-term follow-up in these cases is mixed with preservation of volumization but loss of tip support reported when IRC is used. Considerable warping can also occur over time.

Another homograft, acellular dermal matrix (ADC; LifeCell Corp., Branchburg, NJ), has been used as a dorsal onlay implant, either alone or in combination with autologous cartilage. ADC provides a three-dimensional collagen scaffold for host tissue ingrowth and fibrosis and can be used to provide subtle volume augmentation (especially in the radix). It can also be used to camouflage irregularities of the dorsum or from other cartilage grafts. At best, only a portion of the volume of ADC will persist long term.

Finally, temporary injectable fillers such as hyaluronic acids and calcium hydroxylapatite have been described for nasal contouring. These are generally simple and effective but temporary solutions, and the long-term safety of permanent filler material in this area is unclear.

Implant Biocompatibility

The body's biologic response to an alloplast is dependent on factors related to both host and implant. The chemical composition, surface electrical charge, surface texture, and porosity all contribute to the specific response that occurs around an alloplastic implant. Simply put, a nasal implant is a rather large subcutaneous or submuscular foreign body. Following implantation, the implant is coated with host proteins such as fibrin, fibronectin, and other proteins that become partially denatured on contact with the implant. These proteins are essential for the subsequent host inflammatory response. The severity, cellular activity, and longevity of this response are determined in large part by the qualities of the implant. Neutrophils and monocytes migrate to the implant surface. When the initial inflammatory response subsides, the neutrophilic content decreases, giving way to macrophage increase and accumulation of giant cells, fibroblasts, and some lymphocytes around the material. A fibrotic response ultimately results, with a capsule of fibrosis around the implant; any fragments, left behind in the manufacturing of the implant, related to surgical technique, or formed as a result of implant degradation in situ, will promote additional inflammatory reactions around each particle of material. Some early implants no longer in use today were found to undergo degradation and released new fragments into the surrounding tissues; a vibrant secondary foreign body response developed and persisted around the implant causing significant collateral damage. By contrast, the three most commonly used solid nasal alloplasts today (expanded polytetrafluoroetheylene [e-PTFE], porous high density polyethylene [PHDPE], and silicone) are associated with quite different early responses, which represent different points on a common spectrum. These implants have been designed to avoid particulate degradation.