Imaging of Cosmetic Facial Implants and Grafts

SUMMARY: A wide variety of implants and grafts have been used for cosmetic facial surgery, including forehead, nose, cheek, lip, and chin augmentation. Some of the implant materials include silicone, expanded polytetrafluoroethylene (Gore-Tex), hydroxylapatite, and porous polyethylene (Medpor). Grafts include bone and cartilage, which can be prepared as “Turkish Delight” for rhinoplasty. Imaged facial implants and grafts can be encountered incidentally or purposely to evaluate complications. Many of these materials have distinct radiologic imaging features and should not be misinterpreted as pathology. Conversely, implant complications should be appropriately recognized by using a focused imaging approach. The purpose of this article was to review the different types of cosmetic facial implants and grafts with an emphasis on their expected and complicated radiologic imaging appearances.

A ccording to the American Society of Plastic Surgeons, a total of 243,777 rhinoplasty surgeries, 46,931 forehead lift surgeries, 20,680 chin augmentation surgeries, and 11,996 cheek implant surgeries were performed in the United States in 2011. 1 On occasion, patients who have undergone facial augmentation procedures present for radiologic imaging. Therefore, it is important to be familiar with the common types of cosmetic facial implants and their complications. The imaging features of these implants differ on the basis of location and composition. Often, implants are used at the same time in different locations to achieve balanced proportions of facial tissues. The imaging features of commonly used material for cosmetic facial implants are reviewed in the following sections and in the Table. [2][3][4][5] It is important to recognize the expected imaging appearances of implants and their complications to avoid misdiagnosing these as neoplastic processes, for instance. 6,7

Forehead
Cosmetic forehead augmentation (browplasty) can be performed for the treatment of frown lines and to mitigate bony deficiencies. 8,9 Popular materials used in the midforehead include soft expanded polytetrafluoroethylene strips and silicone implants. 7 The expanded polytetrafluoroethylene strips (Gore-Tex; W.L. Gore & Associates, Newark, Delaware) are usually 1-to 2-mm thick and positioned in a vertical orientation (Fig 1). On the other hand, shield-shaped silicone implants can cover a relatively larger area, and irregular edges and perforations limit implant motion and capsular contraction. 8

Cheek
Cheek augmentation (malarplasty) consists of adding volume to either the malar or submalar space or a combination of these to compensate for osseous and soft-tissue deficiencies and to elevate the cheek subcutaneous tissues. [10][11][12] Specifically, submalar implants are positioned over the anterior walls of the maxilla (Fig 2). On the other hand, malar implants are positioned over the malar eminences and zygomatic bones in a more superior and lateral position (Fig 3). Combined malar-submalar implants span both the malar eminence and the submalar triangle.
The implants are typically inserted into the subperiosteal pocket via a transoral approach through the canine fossa. 10 In the past, ovoid "button" implants were used for cheek augmentation. Currently, Silastic (Dow Corning, Auburn, Michigan) shell implants are especially popular and have characteristic crescent shapes to match the contours of the underlying anatomy. The implants are available in a variety of sizes and can be further customized intraoperatively. Small holes are sometimes incorporated into the implant to promote tissue ingrowth. In addition, the implants can be secured with sutures or screws. Other materials that have been used for midface augmentation include porous polytetrafluoroethylene (Medpor; Stryker, Allendale, New Jersey) and expanded polytetrafluoroethylene (Gore-Tex). 10,12 Nasal Cosmetic rhinoplasty consists of altering the shape of the nose to achieve a more attractive form and relationship with the sur-rounding facial structures, while attempting to preserve the normal functions of the nose. Augmentation rhinoplasty consists of     adding material to the nose and can be performed by using autograft, such as bone (Fig 4), or alloplastic implants, such as silicone rubber (Fig 5). 13,14 Satisfactory results have also been obtained with cartilage grafts, Medpor, Gore-Tex, and Mersilene (Ethicon, Cincinnati, Ohio) mesh. 1-18 "Turkish Delight" is a unique augmentation preparation used for rhinoplasty composed of diced cartilage mixed with a small amount of the patient's blood and wrapped in Surgicel (Ethicon). 19 Variations of Turkish Delight, consisting of diced polyethylene, have also been used. 17 Different portions of the nose can undergo augmentation, including the nasal dorsum, tip, columella, and combinations of these.
Premaxillary augmentation can be performed as an adjunct to rhinoplasty to treat an excessively deep infranasal sulcus (premaxillary underprojection) and an acute nasolabial angle. 20,21 This can be accomplished by using osteochondral grafts or a strip of alloplastic material, such as silicone, positioned in the midline just inferior to the anterior nasal spine of the maxilla (Fig 6). Some silicone implants have a bat-wing configuration. 20

Lip
Surgical augmentation of the lips (cheiloplasty) can be performed to mitigate the changes that occur with aging, such as the development of perioral rhythides and diminished fullness and ante-   rior projection. 22 Lip augmentation can also be performed in response to fashion trends, in which full lips are deemed a desirable trait. 22 A variety of implants are available for lip augmentation, including fat grafts, musculoaponeurotic system grafts, acellular human dermis, and expanded polytetrafluoroethylene. [22][23][24][25] These can be inserted via incisions made medial to the oral commissures and by threading the implant deep to the submucosal plane. 22 The implants are often given a trapezoidal shape, so that these are thinner laterally to conform to the natural tapering of the lips toward the oral commissures. Gore-Tex lip implants typically measure Ͻ3 mm in thickness so that these are not excessively stiff. 24

Chin
Cosmetic chin augmentation (mentoplasty) can be performed to treat a deficient chin projection, which results from soft-tissue atrophy and retrusion of the mandible. 26,27 Ideally the chin should extend to the level of the vermillion border of the lower lip    in the sagittal plane. 26 Autogenous materials, such as cartilage grafts, have been used in chin augmentation for more than a century (Fig 7). Such grafts can be readily procured during concomitant reduction rhinoplasty, for instance. However, autografts have a tendency to resorb, resulting in loss of cosmetic effect. Consequently, alloplastic chin implants, including Gore-Tex (Fig  8), Medpor (Fig 9), Silastic (Fig 10), and hydroxylapatite (Fig 11), have been introduced. 28,29 Most chin implants are crescentshaped and wider centrally than laterally and are positioned approximately in the midline. Alternate designs such as cleft chin implants that are focally narrow in the midline are also available and should not be thought abnormal. Chin implants are usually inserted in a subperiosteal pocket anterior to the pogonion and inferior to the mental foramen. Relatively stiff submental chin implants (Fig 12) can be inserted in conjunction with liposuction to tighten the skin and optimize the neck-chin angle. 30 A variant of the chin implant is the prejowl implant, which serves to fill in a prominent prejowl sulcus and is often used in conjunction with a midface lift. 26,27 The prejowl implants extend farther posteriorly and are thicker laterally compared with chin implants.

COMPLICATIONS
Essentially all cosmetic facial implants and grafts can incur complications, which include infection, migration or displacement, extrusion, foreign body reaction, heterotopic bone formation, and bone erosion. These complications often warrant imaging evaluation and subsequent surgical removal of the implants. The rate of alloplastic implant removal due to complications has been reported to be 1.9%-4.9%. 16,31 Imaging for early postoperative hematomas and seromas is not routinely performed unless these are larger than expected, there is an increase in size, or there are other associated complications.
Implant-related infections usually occur within the first 2 weeks of surgery and have been reported to occur in 3.2% of nasal dorsum implants, 3.8% of malar implants, and 5.3% of chin implants. 31,32 Proplast (Vitek, Valencia, California) Teflon (Dupont, Wilmington, Delaware), which is an ultraporous composite material, has fallen out of use due to the relatively high incidence    of complications, such as infection, which are reported to occur in 16% of cases. 33 Implant infections can manifest as cellulitis, abscess, draining sinuses, and/or osteomyelitis. MR imaging is particularly sensitive for delineating the extent of the infections, especially early in the course of disease. Fat-suppressed postcontrast T1-weighted sequences are particularly useful and often show enhancement within and surrounding the implant pocket (Fig 13). If there is incomplete fat suppression due to technical problems, short tau inversion recovery sequences can be helpful. Placement of external markers over palpable lesions and draining sinuses can facilitate determination of the necessary FOV and subsequent interpretation because the disease involvement can sometimes extend far away from the implant itself. Late infections can mimic malignancy, such as squamous cell carcinoma. 7 Infections can also be associated with implant displacement and extrusion.
Chronic inflammation and foreign body giant cell reaction tend to be most exuberant with Proplast Teflon but can also be encountered with newer alloplastic implants, such as Medpor. 33,34 On histology, intracytoplasmatic phagocytosis of disintegrated implant material is characteristic. Cross-sectional imaging can reveal ill-defined soft tissue surrounding the implants (Fig  14). The abnormal soft tissues can enhance and form more focal masslike areas as well.
Implant migration or displacement is an uncommon complication that can certainly result in undesirable changes in cosmesis as well as serious complications, such as scleral erosion. 35 3D CT surface renderings are particularly useful for delineating the po-sitioning of the implants (Fig 15). Although sutures, screws, fibrous capsule formation, fibrovascular in-growth, and osseous incorporation can secure implants in position, the implants can become displaced by trauma, fluid collections, and bone erosion.
Bone erosion is a relatively frequent finding, occurring with most Silastic chin implants. 36,37 The degree of erosion is usually mild and benign in nature; however, the implants can expose dental roots, resulting in pain (Fig 16). Chin implants can also erode into the mental foramen and compress the nerve. CT with dental scanning parameters is the technique of choice for evaluating symptomatic bone erosion caused by chin implants. 36 Implant extrusion is a rare event that is predisposed by an underlying infection, which can make the overlying tissues relatively friable. 38 Implants can extrude through the overlying skin or incision site, such as the intraoral approach for cheek implants, and even into the maxillary sinuses by eroding of the cheek implant though the anterior maxillary sinus wall (Fig 17). 39 Heterotopic new bone formation is not infrequently noted adjacent to implants, particularly those in a subperiosteal location. It is usually thin and linear in a distribution corresponding to the periosteum and is of little clinical significance. 36 However, heterotopic ossification is occasionally nodular (Fig 18) and can cause cosmetic deformity. 2 CT is the technique of choice for evaluating heterotopic ossification because some implants can display signal characteristics that are nearly identical to heterotopic bone on MR imaging.  Cheek implant inflammation with foreign body giant cell reaction. The patient presented with bilateral cheek swelling many years after receiving the implants. Axial CT images in bone (A) and soft-tissue (B) windows show bilateral Proplast Teflon implants with inflammatory changes in the overlying soft tissues (arrows). Note the crude morphology of the implants, which date to the early 1990s. The implants were subsequently removed, and pathology demonstrated a combination of attenuated fibrous tissue with focal foreign body giant cell reaction and acute chronic inflammation.

CONCLUSIONS
Many types of implants and grafts are now available for facial augmentation. Radiologic imaging plays an important role in the assessment of cosmetic facial implants. MR imaging and CT with multiplanar reformats and, in some cases, 3D surface renderings are useful modalities for characterizing facial implants and their complications.