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Calvarial Bone Grafting in Rhinoplasty
Calvarial bone grafting is an established method of craniofacial reconstruction in facial plastic surgery. Konig and Muller were the first to describe autogenous calvarial bone grafting in 1890, advocating a combined osteocutaneous flap. Smith, Abramson, and Tessier popularized the technique for modern craniofacial reconstruction. More recently, split calvarial bone grafts have been shown to be safe and effective grafts for nasal reconstruction and a viable alternative to autogenous cartilage and alloplastic implants for dorsal nasal augmentation.
Two groups of patients undergoing rhinoplasty and/or nasal reconstruction require materials to augment the nasal dorsum. The first group has saddle nose deformity, arising from traumatic, infectious, idiopathic, or iatrogenic conditions. The second group of patients has a congenitally platyrrhine nose, characterized by a low, wide dorsum, poor tip projection and definition, and an acute nasolabial angle. In modern reconstruction of the nasal dorsum, an ideal implant provides structural support, long-lasting augmentation, limited mobility, and reasonable resistance to infection.
Four categories of facial implants are in use today: alloplastic materials, homografts, xenografts, and autografts. Alloplasts are implants made of chemically composed polymers. Homografts refer to grafts obtained from a donor of the same species and include irradiated and nonirradiated cartilage, bone, and soft tissue. Xenografts refer to materials obtained from different species and are not used in contemporary augmentation rhinoplasty. Autografts are materials harvested from the patient's own body and include bone, cartilage, and soft tissue grafts.
Alloplasts
Presently, the literature supports the use of both alloplastic and autogenous material for nasal reconstruction. Employing alloplastic materials shortens the length of an operation by eliminating the harvesting step, eliminates donor site morbidity, and can be easily tailored to conform to the defect. These materials are available in unlimited quantities and undergo minimal resorption. However, there are several important disadvantages to their use that have prompted many surgeons to avoid their use when possible. These disadvantages include foreign body reaction at the implant–tissue interface, a limited ability to withstand infection, and a tendency to migrate. These implants must be placed under highly sterile conditions, preferably in a bed of healthy, robust native tissue; tension over the implant and compromise to the vascular supply of the recipient bed must be avoided.
Homografts
Homografts represent another option for nasal reconstruction, and irradiated costal cartilage has been advocated as the preferred graft for dorsal nasal reconstruction by some surgeons, especially for those with extruded nasal alloplastic implants. Irradiated costal cartilage is harvested from cadavers that meet the same criteria required for organ donation (Venereal Disease Research Laboratory, hepatitis B, human immunodeficiency virus, tuberculosis, and slow virus testing). After harvest, the graft is irradiated with 30,000 to 40,000 Gy of ionizing radiation to eradicate potential pathogens. Benefits of homografts include their availability, low infection rates, minimal host immunogenic response, and decreased operative times. The use of homografts is limited by their tendency to resorb, sometimes unpredictably; resorption rates as high as 80% have been reported at 2 years. Symmetric contouring of the graft, placement in areas of low mobility (such as the nasal dorsum), and K-wire insertion are techniques that have been developed to decrease the rate of absorption. Homologous rib is best reserved for the elderly, to decrease operative times and donor site morbidity.
Autologous Implants
Given the shortcomings of allopasts and homografts, many nasal surgeons believe that the preferred type of implant for correction of saddle nose deformities or severe structural deficiencies is autogenous cartilage or bone. Autologous tissue is favored for its biocompatibility, low rate of infection and extrusion, and limited inflammatory response. It also lacks the risk of disease transmission that is present in homologous implants. Despite the limited availability and donor site morbidity, autologous implants remain the standard to which all other implants are compared.
Cartilage
Cartilages is an extremely popular graft material for most rhinoplasty surgeons and can be harvested from the septum, concha, or rib. Septal and conchal cartilages do not provide sufficient material for repair of most saddle nose deformities or severe tip structural deficiencies. Rib is the only source of cartilage that provides the structural support required for major nasal reconstruction. A significant advantage of rib is that it is readily available, although moderate absorption rates and a tendency to warp have been reported. Removal of the perichondrium, accompanied by symmetric carving using the central core of cartilage for dorsal augmentation, is one technique described to reduce warping. Internal fixation of the graft with a K-wire can also potentially reduce warping and decrease delayed graft malposition. Donor site morbidities include the possibility of pneumothorax, a likelihood of postoperative pain, temporary atelectasis, potential chest wall deformity, and a visible scar. In older patients, ossification of the cartilage can make carving and shaping of costal cartilage difficult.
Bone
Autologous bone is rigid, provides excellent support, and can be contoured with an otologic drill to create the desired contour. For nasal reconstruction, osseous rib and iliac crest are common sources of endochondral bone, while calvarium is the most common source of membranous bone. Osseous rib has an unpredictable pattern and amount of absorption, with an inherent tendency to distort its shape over time. The iliac crest yields plentiful bone, which can be fashioned to fit a variety of defects, similar to calvarial grafts. However, absorption has been problematic, and donor site issues, including pain and walking impairment, have been substantial.
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