Grafting in Modern Rhinoplasty

Rhinoplasty is considered one of the most technically difficult surgical procedures because of the limited access and requirement for three-dimensional visual perception and manipulation. Grafting is an essential part of primary and secondary rhinoplasties and forms the foundation for a successful functional and aesthetic outcome. Septal cartilage is the most commonly used grafting material, although many reliable alternatives exist. No randomized clinical trials have been conducted comparing graft materials and techniques for specific indications. In this review, the authors discuss the most common grafting materials and configurations used in the modern rhinoplasty.

Key points

  • Grafts are applied for structural or cosmetic purposes to augment the existing nasal substructure. Stable clinical outcomes are achieved when the osseocartilaginous framework maintains its geometry and permits passive draping of the soft tissue.

  • Autogenous cartilage, harvested as septal, costal, and auricular grafts, is the most biocompatible material.

  • Commercially available grafts include processed homografts and synthetic implants. Although these can be obtained in abundant supply, they are known to cause long-term complications that are not seen with autogenous cartilage.

  • Certain grafts are routinely used by all rhinoplasty surgeons, and these common configurations are discussed. To a certain extent, the choice of grafting technique depends on surgeon preference and experience.

Introduction

Rhinoplasty is the third most commonly performed invasive cosmetic surgical procedure behind breast augmentation and liposuction. It is considered one of the most technically demanding cosmetic surgeries because of its limited access and complex 3-dimensional anatomy. Furthermore, even with adequate experience, many surgeons often have difficulty predicting and accounting for subtle long-term postoperative changes.

Embryologically, the developing nasal septum has 2 components that mirror the pattern of palatal development. The lesser anteroinferior segment of the septum arises as a continuation of the medial nasal processes after they fuse to form the primary palate. The remaining bulk of the nasal septum derives from the frontonasal process, which grows inferiorly to fuse with the palatal shelves of secondary palate and the anterior septum of the primary palate. The result is a complete separation of the right and left nasal chambers. Like other craniofacial structures, the nasal septum is composed of a neural crest core that can differentiate into a variety of skeletal and connective tissue precursors. The septum is completely cartilaginous at birth; however, beginning at birth and continuing through puberty, the bony septum undergoes endochondral ossification. This process shapes the vomer and the perpendicular plate of the ethmoid. The anterior septum persists as the quadrangular cartilage, which is a smooth, elastic hyaline cartilage that is composed of a type II collagen. Although cartilage is metabolically active, it is avascular and relies on diffusion to obtain adequate nutrition. Therefore, following injury, cartilage has a limited capacity for repair and regeneration. Grafting the nasal region with cartilage is a technical and biologic challenge because long-term graft survival is less reliable compared with skin and bone.

Although the entire nose was originally considered a single unit of the face, authors have long come to appreciate the complexities of functional and aesthetic nasal anatomy. Burget and Menick first described the principles of nasal aesthetic subunits, which divided the external nose into a tip, dorsum, sidewalls, alar lobules, and soft tissue triangles. Other authors have since offered their modifications and even created separate classifications based on skin quality, light shadows, and underlying support. The nasal framework is best studied by dividing the nose into horizontal thirds. The upper third is supported by a bony vault, whereas the middle and lower thirds overlie a sophisticated cartilaginous substructure.

Grafting is an essential component of primary and revision rhinoplasties and is performed for structural and/or cosmetic purposes. The reinforcement provided by structural or functional grafts permits the nose to resist static gravitational forces and dynamic forces that are applied during animation and respiration. There is tremendous variation in graft nomenclature, and this is often a source of confusion. Grafts are classified by their material, shape, number, location, or function. Furthermore, grafts are globally categorized as being either viable or nonviable. A nonviable graft has no direct contact to skin and is frequently used to provide structure. A viable graft has direct contact with the skin and is typically used for cosmetic purposes. Unfortunately, the evidence supporting individual graft selection is limited. To a certain extent, the choice of graft for a given purpose is subject to provider preference and comfort. No randomized clinical trials have been conducted comparing graft materials and techniques for specific indications. Luckily, different grafts are deployed reliably with successful outcomes. In this review, we describe the most popular grafting materials and introduce common techniques used in the modern rhinoplasty.

Grafting materials

Whenever grafting is necessary, the septal cartilage is the preferred donor site because it is readily available and easy to access. When septal cartilage is unavailable or insufficient, acceptable autogenous alternatives include rib or concha. Other sources of cartilage are available in rare circumstances. For example, during facial feminization surgery the use of cartilage from a concurrent thyroid chondroplasty has been described. Secondary extranasal sources of grafting are more than twice as likely to be required with revision rhinoplasties. Homografts and alloplastic biomaterials are available if autogenous donor sites are exhausted or undesirable. Each material described serves a purpose, but some materials are more versatile than others.

Septal Cartilage

Septal cartilage is widely accepted to be the best grafting material whenever it is available. The septum is always part of the surgical field, and septoplasty is often simultaneously planned for many patients. Septal cartilage is straight and resilient, and the biochemical composition is identical to that of the rest of the nose. Septal cartilage is less firm than costal cartilage, and some surgeons may prefer the later when a high value is placed on structural integrity. Graft size is the primary limiting factor, because a minimum 1 cm of septal cartilage needs to be preserved dorsally and caudally to serve as an L-shaped strut. The amount of available septal cartilage is subject to individual variability and is estimated with preoperative imaging. Postoperatively, septal perforation may require secondary surgical correction if the mucoperichondrial flaps are injured through and through.

Auricular Cartilage

The conchal bowl is accessed through either an antihelical or postauricular approach. The posterior approach has the benefit of a well-hidden incision, but proper technique results in inconspicuous scaring with either technique. During harvest, care must be taken to preserve the antihelix and the crus helix, the latter of which divides the conchal bowl into the cymba and cavum. Conchal cartilage is generally thicker and more pliable than the septal cartilage. The entire segment possesses a curvature that may be advantageous for certain locations. The cymba concha is wider and thinner than the cavum concha. Because of its 3-dimensional contour and resemblance, the concha is the optimal choice for lower lateral cartilage and alar reconstruction. The firmness, thickness, and concave shape of the cavum concha make it favorable for use as a shield graft. The intervening extension of the helical root is the most robust portion of the conchal graft, and as such it is used as a columellar strut.

In the graft-depleted patient, the tragal cartilage graft is considered a salvage procedure. One cadaver study determined that the mean graft size that could be reliably harvested without visible deformities was 21.6 mm by 15.3 mm. Those grafts were approximately 1 mm thick and similarly curved along the long axis. As with conchal cartilage, a stacked configuration or other modification is required to create a straight graft.

Costal Cartilage

The costal cartilage graft is the procedure of choice for total nasal reconstruction because of its volume and strength. A tremendous amount of cartilage can be harvested from the rib’s attachment to the sternum, and this abundance of material is sufficient to reconstruct even the most deficient dorsum. Costal cartilage has more than 4 times the average surface area of auricular cartilage, and donor segments up to 5 cm in length are possible. Exposure of the fifth or sixth rib is straightforward; however, the greatest care must be taken during dissection of the cartilaginous cap away from the underlying parietal pleura ( Fig. 1 ). Whenever possible, the left ribs are preserved to avoid masking cardiac pain postoperatively.

Fig. 1
Intraoperative dissection for harvesting a costal cartilage graft. Note the osseocartilaginous junction, which marks the lateral extent of available cartilage.

The disadvantages of harvesting costal cartilage include donor site morbidity, graft warping, and graft calcification. The donor site scar is typically well hidden. However, before closure, the wound should be filled with saline and examined for bubbling during Valsalva maneuver. Chest tubes are not needed for most small pleural tears. Costal cartilage has an inherent and unpredictable tendency to warp over time, and this can cause residual deformity in the reconstructed nose. Strategies to reduce warping include increasing graft thickness, performing balanced cross-sectional carving with central harvest, including a chimeric osseous framework, and using internal fixation with Kirschner wires or screw fixation. Older patients have greater calcification of their costal cartilage. This calcified cartilage is less prone to deformation, but it is also more difficult to harvest and carve and is less predictably resorbed by the body.

Homograft Costal Cartilage

Nonautogenous grafts are composed of either synthetic or nonsynthetic materials, the latter of which include homografts. Irradiated homograft costal cartilage provides the option for structural grafting without the requirement of a separate donor site. These grafts are obtained from prescreened donor cadavers and subjected to 60,000 Gy of radiation. As with all donor tissue transfers, disease transmission is a theoretic possibility that is almost nonexistent in clinical practice. The primary concerns with irradiated homografts are the increased tendency to experience warping, resorption, and infection compared with autografts. Resorption is particularly problematic because the graft is often applied as a load-bearing graft. Newer processing techniques have been described to overcome the limitations with irradiated grafts. Fresh frozen, nonirradiated costal cartilage is decontaminated using light surfactant to remove blood, lipid, and cellular components and antibiotic solution to remove donor pathogens. Because there is no irradiation, this processing technique theoretically sterilizes the graft without affecting its viability. A recent study of 50 patients who underwent secondary rhinoplasty reported satisfactory outcomes without significant graft resorption. The one case of infection that the authors encountered was treated effectively with light debridement and antibiotics.

Alloplastic Materials

The ideal facial implant is biocompatible, inert, becomes well integrated, and is easily contoured. Synthetic implants have many advantages including the lack of additional donor site, abundant supply, and the ability to be patient specific and maintain a reliable shape without concern for resorption. Commonly used alloplastic materials include silicone, porous high-density polyethylene (Medpor, Stryker, Kalamazoo, MI), and expanded polytetrafluoroethylene (Gore-Tex, W.L. Gore and Associates, Newark, DE). It is our opinion that the use of synthetic implants be restricted to immobile areas, such as the nasal dorsum. In general, alloplastic materials are often avoided in rhinoplasty because of safety concerns. It should be noted that silicone is still commonly used in Asian rhinoplasties because of its low cost, easy availability, and familiarity among providers and patients.

The physical characteristics of alloplastic implants determine their biologic behavior. Medpor, Gore-Tex, and silicone are all commercially available as sheets or preformed blocks. In addition, Medpor is thermoplastic and can be molded in situ to the desired shape and contour. Both Medpor and Gore-Tex are porous implants that allow for soft tissue ingrowth. Pores as narrow as 1 μm permit the translocation of bacteria, whereas macrophages require pore diameters of 30 to 50 μm. Because the pore size of Gore-Tex implants is between 10 and 30 μm, there is theoretically an increased risk of infection because of its semipermeability to bacteria. Medpor implants have pore sizes between 100 and 300 μm, and this feature is thought to reduce their incidence of infection. Smooth, nonporous implants, such as silicone, rely on fibrous encapsulation for stabilization. All synthetic implants are prone to migration and extrusion; however, silicone implants seem to carry the greatest risk of both ( Fig. 2 ). Implant retrieval rates have been estimated at 12%, 4.5%, 3.6%, and 2% for silicone, Medpor, Gore-Tex, and combined materials, respectively. As a general rule, oversized implants should be avoided, and recipient tissues should be thick, well vascularized, and closed with minimal tension.

Apr 19, 2021 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Grafting in Modern Rhinoplasty
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