Facial Implant Information

Currently available facial implants are considered biomaterials.

The National Institute of Health defines biomaterial as “any substance or combination of substances, other than drugs, synthetic or natural in origin, which can be used for any period of time, which augments or replaces partially or totally any tissue, organ or function of the body, in order to maintain or improve the quality of life of the individual”.

The following are the characteristics of “the ideal implant”

1. Inert, causes no foreign body reaction
2. Resistant to infection
3. Sterilizable
4. No donor site morbidity
5. Nontoxic, non-carcinogenic
6. No resorption
7. Simplifies procedure (time, complexity)

Patient tissue, termed autologous tissue is preferred over alloplastic implants when the following conditions apply:

1. Lack of soft tissue coverage
2. Radiation
3. Compromised vascularity
4. Poor quality of surrounding tissue

The long-term results of autologous bone grafting is disappointing in the facial skeletonfor the following reason:

The fate of onlay bone graft is unpredictable due to resorption and factors that impact its subsequent remodeling. Revascularization of the bone graft makes it susceptible to osteoclast activity, resulting in resorption and volume loss. The functional stresses that the recipient site places on the bone graft, determined by regional musculoskeletal forces and deforming forces of the overlying soft tissue envelope, impact the volume persistence of onlay bone grafts.

• Prefabricated polymers used for facial reconstruction include

1. Porous polyethylene (Omnipore; Matrix Surgical, Atlanta, GA; Medpor; Stryker, Kalamazoo, MI)
2. Polymethyl methacrylate (Hard-Tissue Replacement (HTR) polymer; Biomet, Jacksonville, FL)

Biomaterials (facial implants) can be placed in the facial skeleton

as non-load bearing inlays or as onlay for facial augmentation
The material of choice in load-bearing reconstruction is
autologous bone

The indications for alloplastic facial augmentation in adults include:

1. Skeletal enhancement
2. Reconstruction of secondary facial skeletal deformity from facial trauma
3. Alternative to orthognathic surgery when occlusion is acceptable or has been orthodontically corrected
4. Adjunct to orthognathic surgery
5. Rejuvenation of the midface and/or periorbital region
6. Treatment of Graves ophthalmopathy (in conjunction with other modalities)

The most common sites of alloplastic facial augmentation include:

1. Chin
2. Mandible
3. Malar
4. Infraorbital rim
5. Piriform aperture

The biomaterials commonly used for facial skeletal augmentation in adults are

1. Metals (for fixation)
2. Polymers (silicone, polytetrafluoroethylene, acrylic, polyethylene, polymethyl methacrylate)
3. Ceramics (hydroxyapatite)

The body respond differently to silicone and porous implants.

Smooth implants, such as silicone, result in formation of a smooth-walled capsule often resulting in underlying bone resorption. Porous implants allow tissue ingrowth, and have a less dense and well-defined capsule with less tendency for underlying bone resorption.

Advantages of silicone implants include:

1. Can be sterilized by steam or irradiation
2. Can be carved with scissors or scalpel
3. Can be stabilized with screw or suture
4. Can be removed easily because of capsule formation
5. No known clinical or allergic reaction to silicone implants

Disadvantages of silicone implants include:

1. Resorption of the underlying facial skeleton (especially the chin)
2. Implant migration and malposition if not fixed
3. Visible fibrous capsule when placed under a thin soft tissue envelope
4. Higher infection rate than porous polyethylene

Major advantages of porous polyethylene (Omnipore, Medpor) include:

1. Porosity allows soft tissue ingrowth
2. Allows some flexibility and adaptability of the implant
3. Less likely to migrate or erode underlying bone
4. Easy fixation with screws
5. Easy contouring with scalpel or power equipment without fragmenting
6. Lower infection rate than silicone

Disadvantages of porous polyethylene (Omnipore, Medpor) include:

1. Requires dissection of a larger pocket for placement than smooth implants
2. Soft tissue ingrowth makes implant removal more difficult

Implants are best placed in the subperiosteal plane for facial skeletal augmentation.

They should be placed in the subperiosteal plane because dissection is safe to peripheral nerves and is relatively bloodless. It also allows direct visualization of the facial skeleton and, therefore, more precise augmentation of the skeletal contour.

Paranasal augmentation can benefit patients in the following situations:

1. Simulates the visual effect of LeFort I advancement and other skeletal manipulations
2. Increases the projection of the nasal base and opens the nasolabial angle
3. Increases nasal tip projection by elevating the nasal base
4. Lessens the depth of the nasolabial fold by effacing it from below

A remote surgical approach should be used for paranasal augmentation.

Intraoral incision, the medial extent of which is made just lateral to the piriform aperture to avoid placing the incision directly over the implant

Multiple surgical approaches can be used for malar augmentation.

Intraoral or extraoral (subciliary, transconjunctival, preauricular, and coronal) incision

Asymmetry is the most common complication after placement of a malar implant.
Asymmetry due to malposition or migration (particularly with smooth silicone implants)

There are two surgical approaches used for chin augmentation.

Intraoral or submental incision

Disadvantages of intraoral incisions for placement of chin implants include:

1. Superior malposition of implants
2. Lower lip dysfunction from division or detachment of the mentalis muscle
3. Poor visualization of the mental nerve

The most common complication after placement of a chin implant is temporary lip numbness.

Hypoesthesia of the lower lip (from neuropraxia of the mental nerve) is usually transient and typically resolves with time.

Infraorbital rim implants can be used to correct a “negative vector” deformity.
Infraorbital rim implants can provide convexity to the deficient upper midface skeleton.

Common complications after alloplastic facial augmentation include:

1. Hematoma
2. Implant-related infection
3. Extrusion or exposure
4. Implant malposition/ migration
5. Facial asymmetry
6. Sensory nerve dysfunction
7. Palpability

The treatment for implant-related infections most often requires implant removal.

1. Implant removal, antibiotics, and appropriate wound care
2. Implants may be replaced in 6–12 months

REFERENCES
Cenzi R, Farina A, Zuccarino L, Carinci F. Clinical outcome of 285 Medpor grafts used for craniofacial reconstruction. J Craniofac Surg. 2005; 16:526-530.
Chen NT, Glowacki J, Bucky LP, Hong HZ, Kim WK, Yaremchuk MJ. The roles of revascularization and resorption on endurance of craniofacial onlay bone grafts in the rabbit. Plast Reconstr Surg. 1994; 93:714-722.
Chim H, Gosain AK. Biomaterials in craniofacial surgery: experimental studies and clinical application. J Craniofac Surg. 2009; 20:29-33.
Doumit G, Abouhassan W, Yaremchuk MJ. Aesthetic refinements in the treatment of Graves ophthalmopathy. Plast Reconstr Surg. 2014; 134:519-526.
Gosain AK. Plastic Surgery Education Foundation DATA Committee. Biomaterials for reconstruction of the cranial vault. Plast Reconstr Surg. 2005; 116:663-666.
Gosain AK, Chim H, Arneja JS. Application specific selection of biomaterials for pediatric craniofacial reconstruction: developing a rational approach to guide clinical use. Plast Reconstr Surg. 2009; 123:319-330.
Hench LL, West JK. Biological applications of bioactive glasses. Life Chem Rep. 1996; 13:187-241.
Lin KY, Bartlett SP, Yaremchuk MJ, Grossman RF, Udupa JK, Whitaker LA. An experimental study on the effect of rigid fixation on the developing craniofacial skeleton. Plast Reconstr Surg. 1991; 87:229-235.
Matros E, Momoh A, Yaremchuk MJ. The aging midfacial skeleton: implications for rejuvenation and reconstruction using implants. Facial Plast Surg. 2009; 25:252-259.
Raschke R, Hazani R, Yaremchuk MJ. Identifying a safe zone for midface augmentation using anatomic landmarks for the infraorbital foramen. Aesthet Surg J. 2013; 33:13-18.
Ratner BD, Hoffman AS, Schoen FJ, et al. Biomaterials Science. St Louis, MO: Elsevier Academic Press; 2004.
Rubin JP, Yaremchuk MJ. Complications and toxicities of implantable biomaterials used in facial reconstructive and aesthetic surgery: a comprehensive review of the literature. Plast Reconstr Surg. 1997; 100:1336-1353.
Williams, D.F. Williams Dictionary of Biomaterials, Liverpool University Press (1999).
Yaremchuk MJ. Facial skeletal reconstruction using porous polyethylene implants. Plast Reconstr Surg. 2003; 111:1818-1827.
Yaremchuk MJ. Making concave faces convex. Aesthetic Plast Surg. 2005; 29:141-147.
Yaremchuk MJ, Chen YC. Enlarging the deficient mandible. Aesthet Surg J. 2007; 27:539-550.
Yaremchuk MJ, Doumit G, Thomas MA. Alloplastic augmentation of the facial skeleton: an occasional adjunct or alternative to orthognathic surgery. Plast Reconstr Surg. 2011; 127:2021-2030.
Yaremchuk MJ, Israeli D. Paranasal implants for correction of midface concavity. Plast Reconstr Surg. 1998; 102:1676-1684.
Yaremchuk MJ, Kahn DM. Periorbital skeletal augmentation to improve blepharoplasty and midfacial results. Plast Reconstr Surg. 2009; 124:2151-2160.