Malar and Submalar Alloplastic Implants 

Updated: Nov 16, 2015
Author: Gregory D Pearson, MD; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS 

Overview

Background

Alloplastic facial implants offer the reconstructive surgeon certain advantages over autogenous tissue, including availability of material, simplification of operative procedure, and limited donor site morbidity. Depending upon the desired surgical result, the implant must be chosen based upon its physical properties. In order to prevent extrusion or infection, proper preoperative planning and operative technique are essential.

History of the Procedure

The use of alloplastic implantable materials to achieve improved facial contours has been noted for centuries. Early implants consisted of naturally occurring materials (eg, gold or ivory), while modern implants are complex materials such as ceramic, silicone or carbon-based polymers.[1] The search for the perfect implant material is still under way.

Problem

The appearance of the malar aesthetic unit is a strong component of western youth and beauty. A round, more prominent malar area conveys a youthful, healthy appearance. As aging occurs, the malar soft tissues atrophy and descend, creating an aged face.

Malar deficiencies can be classified as congenital or acquired, Bony deficiencies or asymmetries are typically treated with osteotomies (possibly requiring bone grafts) or implants. Soft tissue deficiencies can be corrected with soft tissue resuspension, injectables (eg, fat injection), or implants. See the images below.

Frontal view of patient before and after insertion Frontal view of patient before and after insertion of malar implants.
Side view of patient before and after insertion of Side view of patient before and after insertion of malar implants.

Etiology

Malar deficiencies and asymmetries can be classified as congenital or acquired. Examples of congenital defects include Treacher Collins Syndrome, hemifacial microsomia, and familial inheritance of physical attributes. Acquired deficiencies can be due to trauma, radiation, or aging. Aging, smoking, and sun exposure lead to atrophy and sagging of the soft tissues overlying the zygoma, giving the face a less youthful appearance.

Ethnic differences in malar position, symmetry, size, and definition should be considered when contemplating alloplastic implantation. For example, people of Asian descent typically have flatter, wider malar areas than people of Northern European decent.

Presentation

A thorough and critical analysis of a patient’s face is required prior to embarking upon malar augmentation.[2] The analysis should consist of bony and soft tissue abnormalities. Noting asymmetries of the face preoperatively and pointing them out to the patient is critical. Having the patient look into a mirror while pointing out asymmetries can be exceedingly useful, as can photographic analysis (postoperatively, the patient will see himself in the mirror and in photographs, and through these formats he will judge the surgical outcome).

For congenital deformities, make certain that skeletal maturity has been reached. For acquired deformities, make certain that no other functional impairments need correction (eg, enophthalmos). Although various authors propose differing techniques for facial analysis, the most important aspect of malar augmentation remains matching the patient to the correct type of implant. Since malar deficiencies vary, the proper implant, placement, and location also vary.

General anesthesia is typically preferred, but, depending upon the size of implant and amount of required dissection, malar implants can be placed using local or general anesthesia. General anesthesia allows a more liberal dissection for patient comfort. A thorough history and physical examination should be performed for each patient, with specific focus on medications or supplements that can cause bleeding, smoking history, and wound healing issues.

Indications

Several general categories of candidates for malar augmentation include the following:

  • Posttraumatic

  • Congenital deformities

  • Midface hypoplasia

  • Very long, narrow face

  • Aged face with atrophy and ptosis of soft tissues

  • Very round, full face

  • Unbalanced aesthetic triangle

The first two categories can be identified by a proper history. If midface hypoplasia is considered, the occlusion should be properly examined and a cephalogram evaluated. Patients in all of these categories may benefit from malar augmentation. (The first three categories are treated more with bony augmentation; the other four use more soft tissue augmentation.)

Malar augmentation in aged, thin, round, or familial unbalanced faces can create a more aesthetically pleasing appearance. Inferior descent of the malar fat pads (as typically seen in aging) can be improved with implants and proper soft tissue resuspension.[3]

Relevant Anatomy

Knowing the location of the infraorbital nerve is critical when performing malar implantation. The nerve is typically located along a plumb line from the patient's medial limbus of the eye. See the image below.

Infraorbital nerve. Infraorbital nerve.

Preservation of the nerve during dissection is paramount. Hypoesthesia can occur following malar implant placement.

Contraindications

A history of radiation, bleeding disorders, problems with healing, or anticoagulant medications are considered strong relative contraindications. Active infection is an absolute contraindication.

 

Workup

Laboratory Studies

The choice of laboratory studies depends upon the medical history of the patient. Routine presurgical labs may include CBC counts, electrolytes, and prothrombin time (PT)/activated partial thromboplastin time (aPTT).

CBC counts may be indicated for a patient with a history of anemia or infection. Electrolyte levels may be indicated for a person taking diuretics. A glycosylated hemoglobin A1C (HbA1C) level to determine glycemic control should be obtained in patients with diabetes mellitus to determine potential wound healing issues. Patients with a bleeding disorder or who are taking warfarin should have their coagulation profile (PT, international normalized ratio [INR], aPTT) checked.

Nutritional labs including albumin, prealbumin, and transferrin levels should be considered if bariatric surgery as been performed or if malnourishment is considered.

Imaging Studies

For complex traumatic or congenital deformities, a CT scan with 3-dimensional modeling can be extremely useful for preoperative planning. Medical models can be generated, allowing the creation of custom-made implants, in particular cases.

 

Treatment

Surgical Therapy

Alloplastic Implants

Alloplastic implants offer many advantages over reconstruction using autogenous tissue, including availability of materials, simplification of operative procedure, and no donor site morbidity. Alloplastic implants can reduce the time under general anesthesia, thereby minimizing the risks that accompany such anesthesia.

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. Varied surface characteristics are available to suit different clinical situations; for example, texturing is useful if tissue adhesion and ingrowth are desired, while smooth capsule formation can facilitate easy implant removal. The ideal implant should be nonimmunogenic, nontoxic, cost-effective, easily tailored and sculpted, and resistant to infection.[4, 1] No implant fulfills all of these characteristics.

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."[5] 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.

Non–carbon-based polymers

Silicone (silastic) was first reported for use in facial implants in 1953. Silicone is highly resistant to degradation and has a high degree of chemical inertness because of its silicon-oxygen bonds and cross-linked nature.[1] 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.[6] It also comes in the form of room temperature vulcanized (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 can be sterilized easily. When silicone implants are fixed against a bony surface in their solid form, long-term stability is very high. Bony erosion has been reported with silicone implants when load is applied to them.[7] 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, and no tissue ingrowth occurs.[1] With solid silicone implants, this capsule usually remains stable throughout the life of the implant. Since tissue ingrowth does not occur, silicone implants are easy to remove by incising the capsule and simply removing the implant. Some authors believe that encapsulation and movement cause most of silicone late complications.[8] 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.[1] Debate exists within the literature whether silicone should be injected into the face for rejuvenation.[9]

Carbon-based polymers

Commonly used carbon-based polymers include polytetrafluoroethylene (PTFE), polyethylene (PE), aliphatic polyesters, and methylmethacrylate.

Although the Food and Drug Administration (FDA) issued a public health advisory in 1991 about the temporomandibular joint implant Proplast, PTFE has reentered the market as Gore-Tex.[1] PTFE (Gore-Tex) consists of a fibrillated polymer of polytetrafluoroethylene, with pores between the fibrils averaging only 22 μm in diameter; this limits tissue ingrowth and eases removal, like silicone.[10] Silicone arrives as block and can be sculpted to the needs of the surgeon. Schoenrock and Reppucci reported only a 0.2% rate of infection necessitating removal in facial implantation.[11]

Solid porous polyethylene implants (Medpor) have become popular implants in the facial skeleton. The pore size (125-250 um) allows tissue in growth and relative incorporation.[12, 8] Medpor implants have been designed in multiple shapes, sizes and dimensions for use in facial alloplastic reconstruction. These implants come off the shelf ready for implantation and can require minimal contouring. In addition, custom-made polyethylene implants have been used for cases of congenital anomalies by this author. Yaremchuk presents a large case series with lengthy follow-up attesting to the durability of these implants with infection rates of 3%. He stresses subperiosteal placement and screw fixation.[8]

Aliphatic polyesters are resorbable materials and do not have durability and permanency like other carbon-based polymers, thereby limiting their usefulness for permanent facial implantation. Methylmethacrylate (MMC), frequently known as bone cement, is formed by mixing a liquid monomer with a powered polymer.[1] This process is extremely exothermic and must be performed outside of the recipient field. MMC becomes encapsulated, is not biodegradable, and is very durable. MMC has a very high bacterial adhesion property, making it susceptible to infection.[1] MMC is frequently used in cranioplasties but has only a limited role in facial implantation because of the abovementioned reasons.

Metals

Gold and titanium are frequently used in facial implantation.[13] Although not typically used for augmentation, both have unique properties that make them useful for facial implantation. Gold, a noble element, does not oxidize after implantation.[1] Gold weights are used frequently in acquired facial nerve palsies for ptosis correction and corneal protection. They are well tolerated, with a low extrusion rate from the upper lid. Titanium is extremely durable for its weight and can achieve osseointegration. Hearing aids and facial prosthetics are attached to titanium screws that have incorporated into the bone.

Ceramics

Hydroxyapatite (HA) is calcium phosphate salt, the principal inorganic compound in bone matrix. HA must cure once placed into the recipient site but is porous enough to allow fibrous ingrowth. Unfortunately, HA is extremely brittle and does not tolerate load well without cracking. Occasionally used for cranioplasties, its role in facial implantation is limited.

Implant Placement

During placement, all opportunities for contamination must be minimized and eliminated. Minimal handling, no-touch technique, and changing gloves prior to implantation have all been advocated. Pocket irrigation with antibiotic solution is frequently employed, as well.

Prior to the start of the procedure, appropriate antibiotics should be administered (depending upon surgical approach) to minimize bacterial loads. Without foreign material present, 100,000 bacteria per gram of tissue are required for infection. In the presence of foreign material, only 100 bacteria per gram of tissue are required. Ideally, antibiotics should be given 30 minutes prior to the start of the procedure in order to reduce the bacterial count. Postoperative antibiotics are also advocated; however, the ideal duration of antibiotics has not been established.

Proper preoperative planning also minimizes the risk of implant infection or extrusion. Placing the implant in a well vascularized area with adequate tissue coverage and pocket laxity is paramount in preventing infection and extrusion. Previous scarring, infection, or radiation increases the risk of negative sequelae from surgical implantation. Although the vascularity of the face is exceptional, scarring and radiation can limit the tissue ingrowth into the implant, which can be desirable.

Preoperative Details

Appropriate antibiotics should be administered prior to the start of the procedure. Assessing the proposed area of implantation for tissue laxity and integrity is paramount.

Intraoperative Details

A myriad of approaches can be used for the placement of malar implants. Most authors recommend subperiosteal placement of the implant.[8] The intraoral approach is popular, as it leaves no visible scar on the face. An upper gingival buccal incision is made, followed by a cranial subperiosteal dissection until the desired pocket is formed. de la Pe ñ a-Salcedo et al advocate an intranasal approach.[14]

An intraoral approach carries a theoretically higher risk of infection due to the bacterial load of the oral cavity. Closing the intraoral incision in layers should be strongly considered. When performing synchronous eye surgery, the implant can be placed via a transconjunctival approach that may require a canthotomy. A subciliary incision can be associated with the risk of ectropion. Coronal and face-lift incisions have also been implemented for placement of these implants.

Proper pocket dissection is essential, followed by securing the implant. In his series, Yarmechuk strongly advocates securing the implant to the bone and credits this with his excellent results.[8] Proper placement, symmetry, location, and desired effects should be judged from multiple views of the patient.

Postoperative Details

The patient should be instructed to elevate the head of bed for the first 24 hours after surgery to minimize postoperative edema. Strenuous physical activity, especially contact sports, must be minimized until healing is complete.

Follow-up

Careful and frequent follow-up is required to monitor for seromas, hematomas, or infections. Malposition of the implant causing facial asymmetry should be watched for as well.

Complications

See the list below:

  • Hematomas and seromas are rare complications and can be minimized by careful surgical technique.

  • Infection and extrusion of alloplastic implants are dreaded complications. Using antibiotics, proper dissection, and implant fixation, Yarmechuk has reduced his acute and late infection rates to a total of 3%.[8]

  • Facial asymmetry following implantation can be prevented by proper intra-operative sculpturing. When asymmetry or malposition occurs, removal of the implant, replacement of the implant, and subperiosteal mid-face resuspension is advocated.[15]

  • The incidences of hypoesthesia (transient), hematoma, infection, and extrusion range from 1-3% depending upon the length of patient follow-up.[12, 8, 16]

Outcome and Prognosis

Most patients are satisfied with the results of malar implantation, with satisfaction rates above 80%.[8, 17]

Future and Controversies

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).