You are in: eMedicine Specialties > Plastic Surgery > FACIAL AUGMENTATION Facial Alloplastic Implants, Cheek: Malar and SubmalarArticle Last Updated: Aug 19, 2005AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Julia MacRae, MD, Consulting Staff of Plastic and Reconstructive Surgery, Christiana Cosmetic Surgery Consultants Julia MacRae is a member of the following medical societies: American Society of Plastic Surgeons Editors: Gregory Caputy, MD, PhD, Chief, Department of Plastic Surgery, Aesthetica Plastic and Laser Surgery Center of Honolulu; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Edward Owen Terino, MD, Director, Department of Plastic Surgery, Los Robles Medical Center; Nicolas (Nick) G Slenkovich, MD, Practice Director, Colorado Plastic Surgery Center at Swedish Medical Center; Al Aly, MD, FACS, Consulting Surgeon, Iowa City Plastic Surgery Author and Editor Disclosure Synonyms and related keywords: implant, alloplastic, augmentation, silicone, malar INTRODUCTIONSection 2 of 11
  Alloplastic facial implants offer the reconstructive surgeon many advantages over autogenous tissue, including availability of material and simplification of operative procedure. Care must be taken to choose the proper implant characteristics for the desired aesthetic result, since each synthetic material has unique properties. With all implant types and materials, careful surgical technique is essential in minimizing the risks of extrusion and infection. History of the ProcedureAlloplastic implantable materials have been used for centuries in cosmetic and reconstructive surgery. Implants placed in the cheek and malar area are used in aesthetic and reconstructive practices to achieve symmetry and balance. From the turn of the century, with early implantable materials in the form of gold cleft palate implants and ivory nasal inlays, to current times, with substitutes for bone and soft tissue, surgeons have continued to search for more suitable alloplastic materials. ProblemThe attractive malar eminence is an important component of the western concept of facial youth and beauty. Flat, hypoplastic cheekbones can make a face look dull and aged, whereas prominent cheekbones contribute to a fresh, youthful appearance. Deficiencies in the malar region can be secondary to trauma, congenital defects, inherited ethnic bony structure, and aging. Malar deficiencies or asymmetries can be corrected by osteotomies or implants. Implants can be composed of autogenous or synthetic materials. EtiologyMalar deficiencies and asymmetries can be due to trauma, congenital defects (eg, Treacher Collins syndrome), inherited bony structure, and aging. Well-defined ethnic differences in malar prominences exist, with Asian individuals having flat, widened malar areas compared to persons of Slavic origin. Aging leads to atrophy and sagging of the soft tissues overlying the zygoma, which gives the face a tired appearance. ClinicalFacial analysis is a critical part of patient selection for malar augmentation. Several techniques of facial measurement analysis of the malar region exist; however, the exact location for augmenting the malar eminence is not universally agreed upon, because the type of malar deficiency varies from patient to patient. Malar implants can be placed using local or general anesthesia. Perform a routine preoperative workup, including consideration of a history of bleeding disorders, problems with healing, or anticoagulant medications. In the evaluation for malar implantation, carefully examine the facial structure and skeleton. Note any asymmetries present in the chart and point them out to the patient, as the patient almost certainly will notice them after surgery. INDICATIONSSection 3 of 11
Several general categories of candidates for malar augmentation include the following:
The first two categories are relatively easy to identify. Flat, thin, and round faces all benefit from malar augmentation, as it balances the face and creates a more aesthetically interesting appearance. In an older patient, malar implants fill out the cheek hollows and grooves associated with inferior displacement of the malar fat pad and soft tissues. Malar grooving is a depression parallel to the nasolabial fold, which is associated with aging and can be improved with malar or submalar implants. CONTRAINDICATIONSSection 4 of 11
Consider a history of bleeding disorders, problems with healing, or anticoagulant medications. WORKUPSection 5 of 11
Lab Studies
TREATMENTSection 6 of 11
Surgical therapyAlloplastic implantsAlloplastic implants offer many advantages over reconstruction using autogenous tissue, including availability of material and simplification of operative procedure. In patients in whom sufficient autogenous material is not available or donor site morbidity is of concern, alloplastic implants can provide optimal volume, without the need for tissue harvest, and decreased exposure to anesthesia time. The wide variety of compositions of synthetic materials allows the surgeon to choose a specific combination of strength, elasticity, and durability for a given procedure. Surface characteristics, such as texturing, allow the surgeon to decide whether tissue adhesion and ingrowth are desired or if smooth capsule formation for ease of removal is preferred. The success of synthetic implants depends upon the interaction between implant material and host reaction. Biocompatibility, defined by Williams in his review of implantable prostheses, is "a state of affairs when a biomaterial exists within a physiologic environment without either the material adversely and significantly affecting the body, or the environment of the body adversely and significantly affecting the material." This biocompatibility depends upon the characteristics of the synthetic material, the proposed location and function of the implant, and the surgical technique of the operator. The ideal implant material is nontoxic, noncarcinogenic, or nonantigenic and is inexpensive, durable, and easily modified by the surgeon. The ideal location for an implant is not always a controllable variable; however, minimizing skin tension over an implant and reducing shear or loading forces on the implant can help ensure its long-term success. Advances in surgery such as sterile and "no-touch" operative techniques and broad-spectrum antibiotics have decreased the incidence of implant infection. Implant materialsThe wide range of implantable synthetic materials can be divided into a few categories: carbon-based polymers, non–carbon-based polymers, aliphatic polyesters, metals, and ceramics. Each of the different substances has a unique profile of strength, flexibility, durability, resistance to infection, and tissue ingrowth, and this profile affects the decision of which material to use for which purpose. Non–carbon-based polymers Silicone (silastic) first was reported for use in facial implants in 1953 (Brown et al). It is highly resistant to degradation and has a high degree of chemical inertness due to its silicon-oxygen bonds. No significant clinical toxicity or allergic reactions have been proven to exist. It can be vulcanized into solid rubber, the most common form for facial implants, and can be carved intraoperatively with a scalpel. It also comes in the form of "room temperature vulcanized," or RTV silicone, which hardens when mixed and can be molded or implanted before it hardens. Silicone implants retain their strength and flexibility though a wide range of temperatures and easily can be sterilized. When silicone implants are fixed against a bony surface in their solid form, long-term stability is very high. However, when subjected to repeated movement with mechanical loading (eg, joint arthroplasties), silicone has a tendency to fragment and deteriorate. Because of its inert nature, the body reacts to silicone implants by forming a capsule. With solid silicone implants, this capsule usually remains stable throughout the life of the implant. Should the implant ever need to be removed, the capsule allows for easier removal of smooth silicone than of porous or textured implants. However, in the liquid or gel form, the silicone is not as inert and can incite a chronic inflammatory reaction. For this reason, liquid silicone should not be implanted directly into human tissues but instead should be contained within a shell or sac. Although a great deal of publicity and controversy has surrounded the issue of silicone breast implant safety, no direct evidence links breast implants and connective tissue disease. As with other alloplastic implants, one complication of silicone implants is extrusion. When silicone implants are placed subcutaneously under thin tissue, extrusion rates may be as high as 5%. Care must be taken to place the implant under a thick, well-vascularized flap without tension and to be wary of placing an implant under previously irradiated or scarred tissue. Carbon-based polymers Carbon-based polymers have been used in various forms for decades and include polytetrafluoroethylene (PTFE), polyethylene (PE), aliphatic polyesters, and methylmethacrylate. PTFE, originally introduced in the 1980s as Protoplast and used for a wide variety of facial implants, was withdrawn by the Food and Drug Administration (FDA) after being used in temporomandibular joint reconstruction. In this setting, repetitive mechanical load led to fatigue with delamination, fragmentation, particulation, and subsequent foreign body reaction to the implant. Currently, PTFE has been re-introduced as Gore-Tex and is available in a variety of preformed implants, blocks, sheets, and strands. Although interstices allow for some tissue ingrowth, Gore-Tex generally forms a fibrous capsule and is easily removed in the event of infection or need for revision. Polyethylene has been used as a bone and cartilage substitute in its ultrahigh molecular weight form since the 1940s. It is currently used in its high-density form (HDPE), which allows for contouring by the surgeon, with sufficient strength. HDPE is similar to PTFE in that it is nonresorbable and highly biocompatible with no tendency for chronic inflammatory reaction. HDPE currently is produced as mesh (Marlex, Prolene) and solid implants (Medpor). The porous surface of HDPE allows for increased fibrous ingrowth leading to stabilization of the implant and less underlying bone resorption but more difficulty in removal of the implant. The pore size of HDPE is 160-368 micrometers, leading to more tissue ingrowth than in materials with pore sizes of less than 100 micrometers such as PTFE. The aliphatic polyesters are carbon-based polymers used extensively for the advantage of being resorbable. They commonly are used as suture material and currently are being marketed as resorbable plates and screws. They maintain their strength for 6-8 weeks and show complete resorption at 1 year. Methylmethacrylate is a polymer commonly used as bone cement. It is fabricated by mixing a liquid monomer with a powdered polymer in an exothermic reaction to form rigid plastic. Once solidified, it forms an impervious, nonbiodegradable material with a capsule. Disadvantages include the material's brittle nature and the toxicity of the monomer, which produces offensive and highly allergenic fumes. Methylmethacrylate has high cure temperatures (as high as 80°C) and very high bacterial adhesion properties, predisposing it to infection. It has been used in the setting of infected mandible fractures and reconstructions in the form of antibiotic-impregnated beads, but as a structural implant, methylmethacrylate is very poorly tolerated in close contact with oral cavity, sinuses, or active infection. Metals Metals have been used in maxillofacial plating for their strength and durability. Stainless steel no longer is used due to its tendency to corrode, and, like the cobalt-chromium alloy Vitallium, its artifacts scatter in radiographic imaging. Titanium, an elemental metal, has had no reports of allergy, toxicity, or tumorigenesis. It does not corrode and has minimal artifact on CT scan or MRI imaging. Titanium, unlike all other implanted metals, achieves osseointegration (ie, direct bone-to-metal contact at the light microscopic level). This interface gives titanium implants greater long-term strength and stability. Ceramics Hydroxyapatite (HA) is calcium phosphate salt, the principal inorganic compound in bone matrix. It can be produced synthetically in a dense form (in which it originally was used in alveolar ridge augmentation), but this dense form of HA was found to be difficult to shape and prone to migration and extrusion. Porous forms of HA have been much more successful and are based on the calcium carbonate structure of marine corals. Their porosity permits fibrovascular and osseous ingrowth. However, HA implants cannot tolerate significant load bearing and tend to crack and fracture. HA also comes in powder and liquid forms, which are mixed intraoperatively to form pure HA without the production of heat (Bone Source). It does not tolerate movement or shear forces, particularly while hardening, thus it generally is used in nonstress craniofacial applications. Despite these advantages, one major limitation of alloplastic implants is their susceptibility to infection. A variety of factors contribute to this risk, including the location of the implant, vascularity of the pocket, operative technique in handling and placing the implant, and the ability of bacteria to adhere to and penetrate the material. Implant placementIdeally the implant should remain uncontaminated throughout its placement, and many surgeons elect to use a no-touch technique in which the implant does not come in contact with gloved hands, skin, or oral mucosa. Rinsing the pocket thoroughly and changing surgical gloves just before placing the implant also may serve to decrease the bacterial contamination load. Under normal circumstances, 100,000 bacteria are necessary to cause clinically significant infection; however, in the presence of synthetic material, this number is reduced to 100. Use preoperative antibiotics when planning an alloplastic implant. Patients undergoing alloplastic biomaterial placement should receive an intravenous antibiotic infusion during placement followed by a postoperative oral course. Other than coverage for Staphylococcus or Streptococcus species, depending on the path of insertion (1 g of a first-generation cephalosporin or 600-900 mg of clindamycin), no specific antibiotic or duration of administration has been demonstrated to be of superior clinical advantage. Carefully consider the vascular supply of the proposed implant site, since poor vasculature as a result of radiation damage, prior surgical scarring, or excessively thin skin covering can adversely affect the ability of the surrounding tissue to fight infection. Generally, facial implants have the advantage of being located in areas of high vascularity; however, design the tissue pocket so it does not place tension on the skin covering the implant, which can cause extrusion. Intraoperative detailsMalar implants can be placed through any of several approaches. The intraoral approach has the advantage of leaving no visible scar and can be performed under local anesthesia. Theoretically, an increase in the risk of infection exists from introducing the implant through the mouth. Injection of bupivacaine with epinephrine can reduce operative bleeding and provide long-lasting anesthesia. The intraoral approach begins with an upper buccal sulcus incision and a subperiosteal dissection toward the zygoma. The dissection should elevate the periosteum off of the zygoma, creating a snug pocket for the implant. Malar implants also can be placed as part of a facelift incision or coronal incision by dissecting down to the level of the zygoma. Subciliary incisions also may be used but add the risk of ectropion to the procedure. The implant may be secured with either nonabsorbable sutures or screws or simply held in place by a tight pocket of periosteum. Confirm implant symmetry and position by standing at the head of the patient and sighting down the face to assess projection. To correct hollow cheeks associated with the aging face, implants may be placed in the submalar region. The standard implant size is 6 mm projection. A smaller 4-mm implant may be used in the patient with a thin skin covering, or a larger 8-mm implant may be used for severe malar hypoplasia. Postoperative detailsPostoperatively, instruct the patient not to engage in any heavy exercise during the healing period, especially contact sports. Follow-upMonitor the patient postoperatively for complications such as malposition, hematoma, or extrusion. COMPLICATIONSSection 7 of 11
An implant occasionally becomes malpositioned and requires revision. Augmentation with synthetic materials does not lead to resorption of the implant, which can be observed with other materials. The incidences of hypoesthesia (transient), hematoma, infection, and extrusion are each less than 1%. OUTCOME AND PROGNOSISSection 8 of 11
In general, the outcome following cheek augmentation is highly satisfactory. FUTURE AND CONTROVERSIESSection 9 of 11
The search for the ideal biocompatible implantable material continues. Researchers are trying to synthesize materials that meet more of the goals outlined above (eg, malleability, strength, resistance to infection). MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Facial Alloplastic Implants, Cheek: Malar and Submalar excerpt Article Last Updated: Aug 19, 2005 | |||||||||||||||||||
