At superficial interface, while
there is a trend toward a thinner capsule with both materials, at all evaluation
points the silicone elicits a significantly thicker capsule than the expanded
polytetrafluoroethylene reinforced with fluorinated ethylene propylene (FEPRePTFE).
At deep interface, there is a
more vigorous capsule formation around the silicone implant than around the
implant of expanded polytetrafluoroethylene reinforced with fluorinated ethylene
This slide demonstrates a thin,
bland, fibrous capsule around the implant of expanded polytetrafluoroethylene
reinforced with fluorinated ethylene propylene (FEPRePTFE). Also seen in the
interstices are numerous cells, capillaries, and collagen.
The silicone implant elicits a
thick, dense fibroadipose capsule (original magnification ×10).
Batniji RK, Hutchison JL, Dahiya R, Lam SL, Williams EF. Tissue Response to Expanded Polytetrafluoroethylene and Silicone Implants in a Rabbit Model. Arch Facial Plast Surg. 2002;4(2):111-113. doi:
From the Division of Otolaryngology, Albany Medical Center, Albany,
Background Expanded polytetrafluoroethylene (ePTFE) and silicone are safe and relatively
Objective To compare, using multiple histologic parameters, the tissue response
to a standard silicone soft tissue implant with the response to a modified
ePTFE implant. The modified form of ePTFE is reinforced with fluorinated ethylene
propylene (FEPRePTFE), which provides increased pliability and material integrity.
Methods The implants were placed into a subperiosteal pocket over the skull
of adult New Zealand white rabbits. At 7, 30, and 90 days after implantation,
en bloc tissue specimens, including skin, implants, surrounding soft tissue,
and underlying bone were harvested for gross and histologic evaluation.
Outcome Measures The tissue response to the implants was assessed with respect to the
number of foreign body giant cells present, the thickness of the fibrous capsule,
and the general inflammatory response (n = 6 for each implant at each evaluation
Results There were no cases of rejection, extrusion, or infection. The silicone
implants elicited a significantly thicker capsule and less neovascularization
Conclusion The FEPRePTFE demonstrated a favorable tissue response when compared
with silicone, particularly in regard to capsule thickness and vascular ingrowth.
VARIOUS ALLOPLASTIC materials are currently used for aesthetic and reconstructive
soft tissue augmentation of the face. Among these alloplastic implants are
silicone and expanded polytetrafluoroethylene (ePTFE). Initially used for
vascular grafts and subsequently for hernia repair, ePTFE has now been used
relatively safely for more than 20 years.1-2
More recently, use of ePTFE has been well documented for facial bony augmentation.3-5 Several clinical studies
have demonstrated the potential advantages of ePTFE. The 2 most significant
advantages are rapid stabilization and limited capsule formation.6-8 The purpose of our study
was to examine the histologic response to a new formulation of ePTFE, one
reinforced with fluorinated ethylene propylene (FEPRePTFE). This change in
configuration has demonstrated improved carvability and firmness and could
prove to be advantageous to clinical application.9
However, adverse effects of any new material must be assessed prior to widespread
clinical use. The biocompatibility of FEPRePTFE has not yet been well described.
The histologic response of this new material was compared with that of silicone
in this study.
Thirty-six adult, female, New Zealand white rabbits, each weighing 2
to 4 kg, were used in the study. Twelve rabbits were assigned to each of the
3 in-life phases at 7, 30, and 90 days. Within each in-life phase, 6 rabbits
were implanted with silicone and 6 rabbits, with FEPRePTFE. The rabbits were
cared for and treated in a manner that complied with guidelines established
by the Guide for the Care and Use of Laboratory Animals (National
Institutes of Health, publication No. 86-23, revised 1985), the New York State
Department of Health Administration, and the Animal Care Committee of Albany
The implantation procedures were performed in a standard veterinary
operating suite. The implantation site was shaved, and the area was prepared
in the usual sterile fashion. A vertical incision was made over the caudal
nasal dorsum through the periosteum. Minimal blunt dissection was used to
create a subperiosteal pocket cephalad to the incision. Several 2.5 ×
0.6 × 0.3-cm implants were carved from the 2 materials, a silicone chin
implant (Extended Chin; Invotec International, Jacksonville, Fla) as well
as an FEPRePTFE chin implant. The implants were then placed into a pocket
just caudal to the external occipital protuberance over the cranium to ensure
that the implant would be placed in a position separated from the incision
site. The periosteum and skin were closed in separate layers with 5-0 monofilament
nylon suture. The skin sutures were removed 7 days after implantation.
The rabbits were killed 7, 30, and 90 days after implantation. The implants
were removed en bloc with 1.5 cm of surrounding tissue and preserved in 10%
neutral buffered formalin for histologic analysis. Five histologic characteristics
were analyzed: (1) the deep bone-implant interface, (2) the superficial periosteal-implant
interface, (3) foreign body giant-cell response, (4) blood vessel formation,
and (5) macrophage response. All of these parameters were compared between
the 2 implants with a paired t test using Excel-Analyse-It software (version 1.62; Analyse-It Software Ltd, Leeds, England).
None of the implants extruded. There was no case of postoperative wound
infection, dehiscence, or hematoma. Also, no statistically significant difference
was found between the 2 implants in regard to foreign body giant-cell response
or number of macrophages at any evaluation period (P
= .44, .17, and .58 for foreign body giant-cell response at 7, 30, and 90
days, respectively; P = .19, .15, and .22 for number
of macrophages at 7, 30, and 90 days, respectively). Neither material resulted
in any significant bone resorption during the study period. The number of
peri-implant blood vessels that formed did not vary between the 2 implants
at day 7 and day 30. However, by day 90, significantly more neovascularization
had occurred in the FEPRePTFE group (P = .004). The
capsule formation, as measured by the deep and superficial interface thickness,
was significantly thicker around the silicone implants at each of the evaluation
periods (P<.001 for deep interface at 7 days; P = .004 and .003 for deep interface at 30 and 90 days,
respectively; P = .01, .002, and .002 for superficial
interface at 7, 30, and 90 days, respectively). This difference is illustrated
in Figure 1 and Figure 2, which also demonstrate that the thickness decreased over
time in both cases.
Facial reconstruction with alloplastic materials has been described
and performed for centuries. A wide range of materials have been tried including
cork, paraffin, ivory, gold, and silver. However, most of these experiments
have demonstrated the alloplastic materials to be unsuitable. While autologous
materials are often preferred, they can be associated with problems such as
absorption, donor site morbidity, warping, increased operative time, and insufficient
The past century has witnessed the advent of many synthetic polymers,
few of which have stood the test of time. Silicone and ePTFE are among the
most widely used polymers and are well described in the facial plastic surgery
literature. These materials have many of the properties first described by
Scales10 as being ideal for an implant. Among
others, these properties include being chemically inert, noncarcinogenic,
unmodified by soft tissue, pliable, and firmly resistant to strain. A relatively
new form of ePTFE, FEPRePTFE was designed with the purpose of enhancing 2
of those ideal properties, namely, pliability and firmness. Our literature
review failed to yield any studies on the histologic response to FEPRePTFE.
Given these improved physical attributes, our goal was to determine if the
tissue response histologically would reveal any adverse reactions. The initial
evaluation was performed at 7 days to examine differences in the acute response.
Since normal healing in rabbits is complete in 14 to 16 days,11
any inflammatory reaction at 30 and 90 days could be assumed to be due to
As the results indicated, none of the implants were extruded or infected.
We also found no evidence of bone resorption during the study period. The
most notable and consistent difference between the 2 implants concerned the
thickness of the surrounding capsule. By day 90, nearly a 4-fold difference
in the superficial interface thickness had developed, with the silicone implant
eliciting a thicker capsule.
One other difference that was noted on histologic examination, but not
quantified among our measured outcomes, was the more abundant collagen ingrowth
in the FEPRePTFE implants than in the silicone implants (Figure 3 and Figure 4).
This finding correlates with the higher vascular migration in the FEPRePTFE
implants, which was statistically significant by day 90. These characteristics
are thought to be the reason behind the more rapid stabilization of this material.8 Although stabilization is desirable, the ideal implant
can also be easily removed if necessary. A limited capsule formation may facilitate
this property. We noted a dramatic and statistically significantly thinner
capsule around the FEPRePTFE implant.
In conclusion, the study demonstrates that FEPRePTFE, a new configuration
of ePTFE, is characterized by a favorable vascular migration and limited capsule
formation. These traits of the FEPRePTFE are advantageous in an implant candidate.
The silicone elicited a more vigorous capsule formation and less neovascularization.
No significant adverse reactions occurred in either implant. However, the
relatively short 3-month examination period may not account for longer-term
adverse effects such as implant migration, extrusion, or infection. Histologic
analysis of ePTFE suggests that these complications are unlikely. Further
clinical studies will more clearly delineate the benefits of FEPRePTEFE in
facial plastic surgery.
Accepted for publication October 31, 2001.
This study was presented at the Combined Otolaryngologic Spring Meeting,
Orlando, Fla, May 13, 2000.
Corresponding author and reprints: Edwin F. Williams III, MD, Division
of Otolaryngology, Albany Medical Center, 47 New Scotland Ave, Albany, NY