Physical examination

Physical examination is the most important element of preoperative assessment and planning. Reviewing life-size photographs with the patient can be helpful when discussing aesthetic concerns and goals as well as demonstrating the asymmetries common to all faces. The recognition of facial asymmetries is important to the surgeon in planning and to the patient in anticipating the postoperative result. As asymmetries become more obvious, it is important to recognize that they are more complex than relative skeletal deficiencies or excess. Rather, they reflect three-dimensional differences that are most easily conceptualized as twists of the facial skeleton that can only be partially compensated for with surgery.

Neoclassical canons and facial anthropometries

For the purposes of painting and sculpture, Renaissance scholars and artists formulated ideal proportions and relations of the head and face. These were largely based on classical Greek canons. Although usually referenced in texts discussing facial skeletal augmentation, neoclassical canons have a limited role in surgical evaluation and planning, because they are based on idealizations. When the dimensions of normal males and females were evaluated and compared to these artistic ideals, it was found that some theoretic proportions are never found, and others are one of many variations found in healthy normal people, or those determined more attractive than normal.² The neoclassical canons do not allow for the facial dimensions that are known to differ with sex and age. Most of these canons of proportion (e.g., the width of the upper face is equal to five eye-widths) are interesting but hold for few individuals and cannot be obtained surgically or, if obtainable, only with extremely sophisticated craniofacial procedures. For these reasons, we have found it more useful to use the anthropometric measurements of normal individuals to guide our gestalt in the selection of implants for facial skeletal augmentation (see Ch. 16). Normal-dimensioned faces are intrinsically balanced. That is, the relations between the various areas of the face relate to one another in a way that is not distracting to the observer. By comparing a patient’s dimensions to the average, the surgeon has some objective basis as to what anatomic area may be amenable to augmentation, and by how much.

Skeletal enhancement

Most often, facial skeletal augmentation is done to enhance facial appearance in patients whose skeletal relationships are considered within the normal range. They want more definition and angularity to their appearance. Other patients desire to “balance” their facial dimensions.

Alternative to orthognathic surgery

Midface and mandibular hypoplasia are common facial skeletal variants. In patients with these morphologies, occlusion is normal or has been compensated by orthodontics. These patients have neither respiratory nor ocular compromise. In skeletally deficient patients whose occlusion is normal or has been previously normalized by orthodontics, skeletal repositioning would necessitate additional orthodontic tooth movement. Such a treatment plan is time-consuming, costly, and potentially morbid. It is, therefore, appealing to few patients. In these patients, the appearance of skeletal osteotomies and rearrangements can be simulated through the use of facial implants. Diagrammatic representations of how implant surgery can mimic the appearance of skeletal osteotomies are shown in Figures 15.1 and 15.2.

Fig. 15.1 (A) Illustration of midface concavity and compensated occlusion. (B) Multiple midface implants provide visual effect of LeFort III osteotomy and advancement but do not alter occlusion.

Fig. 15.2 (A) Mandibular deficiency with compensated occlusion. (B) The visual effect of sagittal split osteotomy and horizontal osteotomy of the chin with advancement has been simulated with mandible and chin implants. Note that the class I occlusion is unchanged. Notice also that the border regularities inherent with skeletal osteotomies are avoided when implants are used.

Adjunct to orthognathic surgery

Alloplastic implants can enhance the results of certain orthognathic surgery procedures, including the LeFort I maxillary advancement, the sagittal split mandibular osteotomy, and the sliding genioplasty.

The LeFort I advancement may fulfill its functional role by creating appropriate occlusal relations but inadequately treats midface hypoplasia since only the lower half of the midface is advanced. This may result in a convexity confined to the lower half of the midface. Alloplastic augmentation of the infraorbital rim with or without malar implants can create a truly convex midface. Posterior mandible implants can camouflage osteotomy-induced irregularities along the mandibular border as well as malpositions of the mandibular angles. Chin implants can correct mandible border contour irregularities after sliding genioplasty (Fig. 15.3).

Fig. 15.3 Infraorbital rim implants create upper midface convexity to compensate for lower midface advancement. Posterior mandible implants can camouflage osteotomy-induced irregularities along the mandibular border as well as malpositions of the mandibular angles. Chin implants can correct mandible border contour irregularities after sliding genioplasty.

Rejuvenation

Traditional concepts of periorbital and midface aging and rejuvenation focus on the soft tissues. Recently, senescent changes in the supporting facial skeleton have been investigated. Findings in these studies revealed retrusion of the midface skeleton and mandible (Fig. 15.4). This diminution in projection would hasten the gravitational-induced descent of their overlying and now, less supported soft-tissue envelope.³ Alloplastic skeletal augmentation can both restore skeletal contours and support the overlying soft-tissue envelope.¹

Fig. 15.4 Illustration showing how the placement of infraorbital rim implant on an aged orbit creates contours that mimic a youthful orbit. (A) CT scan of a youthful face and orbit. (B) CT scan of an aged orbit. (C) Implant augmentation of the infraorbital rim restores a youthful orbital contour.

Provision of these functions supports the concept of selective alloplastic augmentation of the facial skeleton as part of the algorithm for facial rejuvenation and enhancement.

Selective augmentation of the infraorbital rim, malar and pyriform aperture of the old midface skeleton can mimic the contours of its youthful counterpart. Selective augmentation of the chin and mandible can restore youthful contours of the lower jaw.

Skeletal versus soft-tissue augmentation

Both the soft tissues and the skeleton contribute to facial contour and both components are impacted by the aging process. Hence, both soft-tissue and skeletal augmentation can be appropriate to restore youthful facial contours. However, these modalities are not equivalent in their impact on facial appearance. Free fat grafting and the injection of various fillers are intuitive for the restoration of soft-tissue volume loss due to senile atrophy. They have a limited role in simulating the effect of an increase in skeletal projection. Whereas augmenting the facial skeleton results in an increase in the projection of the skeleton, augmenting the soft-tissue volume results in an inflation of the soft-tissue envelope and blunting of the contours of the skeleton. Overaugmentation of either component brings home the point. If overly large implants were placed on the skeleton, the appearance would be too defined and, ultimately, skeletal. If too much fat were placed in the soft-tissue envelope, an increasingly spherical and otherwise undefined shape would result.

Anesthesia and preparation

Facial skeletal augmentation can be performed under either local anesthesia supplemented with sedation or general anesthesia. When implants are placed through intraoral approaches, general anesthesia with nasotracheal or endotracheal intubation assures protection of the airway and the best possible antiseptic preparation of the oral cavity. Patient positioning and exposure for implant placement are also optimized when the airway is controlled. Prior to preparation and draping, a dilute solution of Marcaine with epinephrine is infiltrated into the operative site for postoperative pain control and intraoperative hemostasis. Cephalosporins are administered perioperatively. 0.12% chlorhexidine gluconate oral rinse is prescribed for daily use beginning 3 days before and including the day before surgery.

Facial implant surgery is routinely performed on an outpatient basis.

Incisions

Incisions for skeletal access and implant placement are borrowed from craniofacial and aesthetic surgery. Transconjunctival retroseptal incisions are routinely used to access the infraorbital rim and internal orbit. The lateral extent of the lower lid blepharoplasty incision provides access to the lateral orbit and zygomatic arch. This small cutaneous incision leaves an inconspicuous scar. Skin or skin muscle flap lower lid incisions provide alternative approaches to the periorbital area. Intraoral sulcus incisions are used to augment the midface as well as the mandibular body and ramus. These incisions are made with a generous labial cuff to allow watertight mucosal closure. Chin area augmentation is performed through submental or intraoral incisions. Placement of incisions directly over implants is avoided.

Implant materials

Implant materials used for facial skeletal augmentation are biocompatible – that is, there is an acceptable reaction between the material and the host. In general, the host has little or no enzymatic ability to degrade the implant with the result that the implant tends to maintain its volume and shape. Likewise, the implant has a small and predictable effect on the host tissues that surround it. This type of relationship is an advantage over the use of autogenous bone or cartilage which, when revascularized, will be remodeled to varying degrees, thereby changing volume and shape. The alloplastic implants presently used for facial reconstruction have not been shown to have any toxic effects on the host.⁴ The host responds to these materials by forming a fibrous capsule around the implant, which is the body’s way of isolating the implant from the host. The most important implant characteristic that determines the nature of the encapsulation is the implant’s surface characteristics. Smooth implants result in the formation of smooth-walled capsules. Porous implants allow varying degrees of soft-tissue ingrowth that result in a less dense and less defined capsule. It is a clinical impression that porous implants, as a result of fibrous incorporation rather than encapsulation, have a lower tendency to erode underlying bone or migrate due to soft-tissue mechanical forces and, perhaps, are less susceptible to infection when challenged with an inoculum of bacteria. The most commonly used, commercially available materials today for facial skeletal augmentation are solid silicone, which has a smooth surface, and porous polyethylene.

Silicone

Solid silicone or the silicone rubber used for facial implants is a vulcanized form of polysiloxane. Polysiloxane is a polymer created from interlinking silicone and oxygen with methyl side groups.

Silicone implants have the following advantages: they are easily sterilized by steam or irradiation; they can be carved with either scissors or scalpel; and they can be stabilized with a screw or suture. There are no known clinical or allergic reactions to silicone implants. Because they have a smooth surface, there is no soft-tissue ingrowth, allowing them to be easily removed. Disadvantages to silicone implants include: the tendency to cause resorption of underlying bone; the potential to migrate if not fixed to the underlying skeleton; and the likelihood of its fibrous capsule to be visible when placed under a thin soft-tissue envelope.

Polyethylene

Polyethylene is a simple carbon chain of ethylene monomer. Polyethylene used for facial implants is porous with intramaterial porosity between 125 and 250 µm. The porosity allows fibrous tissue growth into the surface of the implant. The porosity of this implant has both advantages and disadvantages. Soft-tissue growth into the implant lessens the tendency to migrate and to erode underlying bone. Porosity also allows some flexibility and adaptability of the implant. However, its porosity causes its soft tissue to adhere to it, making placement more difficult and requiring a larger pocket to be made than with smoother implants. The soft-tissue ingrowth also makes implant removal more difficult.

The firm consistency of porous polyethylene allows it to be easily fixed with screws and contoured with a scalpel or power equipment without fragmenting.