Facial Shape System
Facial implants, including malar and chin implants, are used to add or restore contour irregularities and/or proportion to the face, for aesthetic (enhancement) or reconstructive (correction of deficiencies) purposes. Traditionally, these implants were made of silicone with resulting overlying soft tissue deformities due to capsule formation around the implant. Hence, there was a need for another material, such as porous polyethylene, to address this clinical issue and improve surgical outcomes.
The new Facial Shape System (Fig 1a and 1b) consists of flexible implants designed for augmenting the contours of the craniofacial skeleton. These implants are made of high density polyethylene, an inert, nonresorbable and biocompatible material. The implants are preshaped to restore several facial anatomical areas, minimizing the need for intraoperative contouring. When necessary, the implants can easily be trimmed with a scalpel or high speed burr. A variety of implant sizes and shapes support different clinical needs. The semi flexible nature of the material allows the implant to conform to underlying bone during fixation, and its porous structure supports fibrovascular ingrowth for host incorporation rather than encapsulation.
The refined implant surface facilitates insertion. Registration tabs assist positioning in terms of verifying symmetry. Furthermore, by submerging them for several minutes in hot sterile saline (over 70 degrees C) manual contour is possible to obtain the desired form, which will be maintained after cooling. Since Facial Shape must be placed directly on the recipient bone, adequate subperiosteal exposure is important to allow visualization of anatomical landmarks and proper placement. Implants are provided sterile and are for single-patient use (nonresterilizable). It is important to prevent contamination through surgical clothing or powder from surgical gloves, and when using intraoral incisions, proper aseptic techniques are highly recommended.
In order to achieve successful implantation, careful preoperative planning should reflect the patient's desires, evaluate the skeletal dimensions, and analyze both the skeleton and the soft tissue envelope. Sizers made from silicone (Fig 2) were developed exclusively to help select the most appropriate implant. The sterilizable and reusable cutting board (Fig 3) with measuring references aids when carving, measuring, and photographing the implants. A positioning instrument (Fig 3) helps to introduce the implant and immobilize it during fixation. Titanium screws from the matrix midface set can be used for this purpose in the appropriate length: self-drilling in 6 mm and 8 mm, self-tapping in 10, 12 and 14 mm, and emergency self-tapping in 6, 8, 10, 12 and 14 mm as required. Screw fixation eliminates any gaps between the inner surface of the implant and the surface of the facial skeleton.
Porous polyethylene implants should not be used, either for load-bearing applications or as a structural support to bone, in cases where active or latent infection is present, in inadequate coverage of healthy vascularized tissue, or in systemic disorders with limited blood supply implications.
The implants are available in two anatomical shapes:
- Chin implants
- Malar implants (see CMF/Midface/Plates).
Chin implants (Fig 1a, above) are used to increase the anterior projection of the chin. They may be used to treat isolated small chins (microgenia) or together with mandible angle implants to camouflage small lower jaws (micrognathia).
The adequacy of chin projection should take into account several variables including the patient's sex, the effect of occlusion on lower lip position, the thickness of the chin pad, and the depth of the labiomental fold. When these variables are not considered, implant augmentation may result in a chin that is unnatural and too large, particularly in women. Chin augmentation with certain shaped implants can create unnatural chin contour. Implants that augment only the chin point produce an abrupt, protruding chin rather than a jaw-chin continuum. Extended one piece implants do not always match the contour of the native mandible. Particularly when placed through small intraoral incisions, minimal inaccuracies in placement or asymmetries in the mid-aspect (chin point) of the native mandible may result in gross distortions and irregularities in the more lateral aspect of the chin.
A flexible titanium connector (Fig 1a) in between both polymer segments introduces a three-part assembly for better anatomical fit, allowing the implant to merge imperceptibly with the native deficient mandible. This solves some of the issues previously mentioned. Depending on patient's needs, there are two shapes for the chin: round and square, with different size options. Registration tabs have been developed as part of these implants to assist positioning.
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