Alloplastic Materials for Facial Skeletal Augmentation$
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Facial Plast Surg Clin N Am 10 (2002) 325–333 Alloplastic materials for facial skeletal augmentation$ Craig D. Friedman, MD, FACSa,b,*, Peter D. Costantino, MD, FACSc aFrom Private Practice, Facial Plastic Surgery, 4 Greystone Farm Lane, Westport, CT 06880, USA bMedical Research and Development, Biomerix, Inc., 41 West 57th Street, New York, NY 10019, USA cDepartment of Otolaryngology, Roosevelt St. Lukes Hospital, 425 West 59th Street, 10th Floor, New York, NY 10019, USA Facial skeletal augmentation continues to be an etal augmentations are onlay in nature with the goals important clinical area for surgeons performing cos- of stability and symmetry paramount. Esthetic guide- metic and reconstructive facial surgery. This article lines have been developed and refined to guide reviews the current state of the art approaches utilizing correction of common facial skeletal deficiencies alloplastic materials. Surgical goals, biomaterials, [1]. Additionally, recent attention has been given to operative techniques, and complication management the role of skeletal changes in aging. Both Binder [2] are discussed. Any discussion of alloplastic materials and Pessa et al [3] have shown the value of skeletal ultimately relates tissue effects to long-term clinical augmentation to enhance other aspects of facial results. It may take a full generation (20 years) to rejuvenation, thereby increasing the importance of appreciate fully most if not all possible tissue effects skeletal augmentation in cosmetic facial surgery. of an alloplastic material; however, biomaterial sci- Inlay applications for skeletal defects (of a trau- ence has developed fundamental principles that matic or oncologic etiology) additionally require vol- should aide the surgeon in choosing the most appro- ume maintenance over time to preclude defect priate alloplast for skeletal augmentation for various reformation. Volume maintenance over time is a key patient groups. advantage of commonly used alloplastic implants. In the past the goal of stable volume was believed to be due to utilization of an inert implant material and minimal tissue response over time. This view of Surgical goals implants has been found to be naive with respect to tissue–implant interface biology. Improved under- Clinical judgment always remains the most standing of interface biology has revealed the limi- important arbiter in selecting the appropriate implant tations of many implants and helped encourage the and surgical approach for an individual patient. development of bioactive implants [4]. Bioactive Patient implant requirements can be routinely clas- implants are biomaterials that allow for biologic sified as either onlay or inlay with regards to the type bonding of tissue to implant, which permits natural of skeletal augmentation. Purely cosmetic facial skel- tissue regeneration as opposed to chronic foreign body or inflammatory reaction. Bioactive interfaces theoretically reduce micro- motion and implant mobility over time. Secure $ This article is reprinted in an abridged format from: implant fixation allows for less opportunity of motion Friedman CD, Constantino PD, Sajjandian A. Alloplastic materials for facial skeletal augmentation. Facial Plast Surg at the interface to induce wound inflammation. Clin N Am 1999; 7(1):95–103. Chronic inflammation over the long term leads to * Corresponding author.. formation of avascular fibrous capsules. Although E-mail address: [email protected] such tissue reaction may by clinically quiesent, it (C.D. Friedman). can lead to gross implant mobility and secondary soft 1064-7406/02/$ – see front matter D 2002, Elsevier Science (USA). All rights reserved. PII: S1064-7406(02)00022-6 326 C.D. Friedman et al. / Facial Plast Surg Clin N Am 10 (2002) 325–333 tissue changes in the long term. Therefore, stable and acterized by various amount of fibrous and fibrovas- secure implant fixation becomes a very important cular ingrowth. Although polyethylene can support clinical goal that affects outcome. surface conduction of viable osteocytes, true inte- grative osteoconduction throughout an implant has not been documented by experimental results [8,9]. Implant materials Fibrovascular ingrowth makes porous polyethyl- ene an attractive implant for facial skeletal augmen- There are four commonly used implant materials tation for the following reasons. First, the ingrowth for facial skeletal augmentation: (1) silicone elasto- stabilizes fixation of the implant. Second, the implant mer, (2) porous polyethylene, (3) expanded polytetra- may be resistant to infection and therefore potentially fluoroethylene (ePTFE), and (4) hydroxyapatite– salvaged in the face of exposure if sufficient vas- calcium phosphate. Detailed implantology informa- cularity is present [10]. Fixation of implants is most tion on these materials can be found elsewhere in this commonly achieved with metal screws. issue. The tissue–implant interfaces exhibited by these materials are important to understand so that Expanded polytetrafluoroethylene clinical effectiveness is maximized. Expanded polytetrafluoroethylene (Gore-Tex, WL Silicone Gore, Flagstaff, AZ) has been used extensively as a soft tissue implant and vascular prosthesis. Various Silicone elastomer is a solid rubber–consistency formulations of fibrils are combined to create polymer of polymethyl siloxane. Due to its relative implants with pores of up to 30 lm. The tissue– inertness as an implant it has been developed for implant interface is usually that of limited fibrous many medical applications and specifically facial tissue ingrowth without significant capsule formation. skeletal augmentation [5]. Preformed shapes for Interesting recent experimental data have revealed nasal, malar, and chin augmentation have been in differential healing responses to ePTFE dependent use for many years. The tissue–implant interface is upon the anatomic site of implantation [11]. Such one of an avascular fibrous capsule. Capsular con- experiments shed light on potential uses in facial traction aides in securing the implant to a fixed implantation and the important questions that remain position over time. Initial fixation of silicone implants unanswered. Preformed chin and malar implants are should be attempted. Many surgeons prefer place- available, but the most common use is to augment the ment in a defined supraperiosteal pocket; others have nasal dorsum in reconstructive surgery. Extensive modified this by use of nonresorbable sutures or experience in this use has been reported with favor- metal screws. able outcomes [12]. Gore-Tex nasal augmentation The most commonly associated unfavorable result ultimately requires comparison with autogenous tis- with silicone implants has been underlying bone sue to make the final assessment of outcomes. resorption. This was identified by Robinson and Shuken [6] in 1969 and has been recounted in many Hydroxyapatite reports subsequently. Matarasso et al [7] have recently summarized these reports and provide findings that Currently, many forms of calcium phosphate and call for caution in advocating silicone chin implants hydroxyapatite biomaterials exist and have extensive for certain patient groups. Despite this well-known use in facial skeletal augmentation. These materials information, silicone implants remain popular and should be classified as bioactive in nature. The readily accepted by surgeons and patients. tissue–implant interface can be categorized as show- ing osteoconduction and osseointegration over time. Polyethylene Interested readers should consult previous reviews for comprehensive details on synthetic bone substitutes High-density porous polyethylene (MedPore, [13]. This discussion only highlights those materials Porex Industries, Fairburn, GA) has gained consid- in general use and emphasizes new information erable acceptance as an implant for facial skeletal relevant to clinical issues. augmentation. It is a particulate high-density polymer Hydroxyapatite biomaterials can be broadly cate- of ethylene that is then fused by a sintering process gorized into ceramic and nonceramic classes. Ceramic into a porous solid material. Pore size ranges from material of a porous nature has been used as an onlay 100 to 300 lm. The material is somewhat flexible and material for facial skeletal augmentation [14]. This readily carved. The tissue–implant interface is char- porous hard material (Interpore, Irvine, CA) has pore C.D. Friedman et al. / Facial Plast Surg Clin N Am 10 (2002) 325–333 327 sizes of up to 300 to 500 lm, which allows for fibro- surgery, to concealed incision surgery, and now mini- osseous conduction at the interface. The main clinical mally invasive endoscopically assisted approaches difficulties have been contouring the edges of the (Louis Morales, personal communication, 1997). Most implant for blending purposes and initial fixation with of the fronto-orbital and midfacial skeleton can be screws, which can lead to problematic implant frac- exposed via coronal scalp incisions and flap elevation. tures. Other surgeons have used granules of porous The midfacial and mandibular skeleton is most often hydroxyapatite for facial augmentation by limiting exposed via intraoral approaches. The nasal region is dissection and exposure to subperiosteal pockets for easily accessed with endonasal incisions. Fig. 1 illus- implant placement and awaiting initial soft tissue trates the authors’ preferred technique for the place- ingrowth healing to stabilize the implant [15]. ment of a chin implant. The