Surgical composite structure having absorbable and nonabsorbable components

A composite structure is disclosed having two or more biocompatible polymers. At least one of the polymers is nonabsorbable. The nonabsorbable polymer is extruded into a fiber. The fiber can be fabricated into a textile structure, for example a woven mesh. The nonabsorbable mesh is then encapsulated with at least one bioabsorbable polymer. The composite structure is useful for repairing anatomical defects, for example in a mammalian abdominal wall.

BACKGROUND OF THE INVENTION 
This invention relates to a surgical composite structure. The structure is 
manufactured from two or more biocompatible polymers. At least one of the 
polymers in the structure is nonabsorbable. 
The nonabsorbable polymer is extruded into a fiber. The fiber can be 
fabricated into a textile structure. The textile structure can be a woven 
mesh. The nonabsorbable woven mesh is then encapsulated with at least one 
bioabsorbable polymer. 
The nonabsorbable portion of the composite structure acts as a 
reinforcement material. Ingrowth of natural tissue is enhanced by the 
controlled degradation of the absorbable portion. 
The surgical composite structure of this invention is useful in the repair 
of defects to the abdominal wall of a mammal. The surgical composite 
structure of this invention may be useful in preventing hernia formation; 
and specifically in preventing hernia formation in an infected area. 
SUMMARY AND DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
A surgical composite structure for mammalian tissue has been invented. The 
composite structure comprises: 
a) a nonabsorbable reinforcing component prepared from one or more fibers, 
at least one of the fibers manufactured from a polymer selected from the 
group consisting of a fiber forming fluoropolymer, polybutester, 
polyester, polyamide, polyolefin, and blends of the same, and 
b) a bioabsorbable component comprising a polymer prepared from one or more 
monomers selected from the group consisting of lactides, carbonates, 
oxalates and lactones. 
In one embodiment, the nonabsorbable component is selected from the group 
consisting of a fiber forming fluoropolymer, a polybutester, and a 
polyester. 
In another embodiment, the bioabsorbable component comprises a polymer 
prepared from one or more monomers selected from the group consisting of 
lactides, carbonates and lactones. In a specific embodiment the lactides 
are selected from the group consisting of glycolide and 
3,6-dimethyl-2,5-p-dioxanedione; the carbonate is 1,3-dioxan-2-one; and 
the lactones are .epsilon.-caprolactone and 1,4-dioxan-2-one. In another 
specific embodiment, the bioabsorbable component is selected from the 
group consisting of lactides and carbonates. 
In yet another embodiment, the nonabsorbable component is in the form of a 
sheet. In a specific embodiment, the bioabsorbable component is laminated 
to at least one side of the sheet. In a more specific embodiment, the 
bioabsorbable component is laminated to both sides of the sheet. In 
another specific embodiment, the nonabsorbable component is in the form of 
a knitted, woven, flat braided, or nonwoven sheet. In a preferred 
embodiment, the nonabsorbable component is in the form of a woven sheet. 
An alternative surgical composite structure for mammalian tissue has been 
invented. The alternative structure comprises: 
a) a nonabsorbable reinforcing component prepared from a plurality of 
fibers, at least one of the fibers manufactured from a polymer selected 
from the group consisting of a fiber forming fluoropolymer, a 
polybutester, a polyester, and blends of the same, and 
b) a bioabsorable component comprising a polymer prepared from one or more 
monomers selected from the group consisting of lactides, carbonates and 
lactones. 
In one embodiment the lactides are selected from the group consisting of 
glycolide and 3,6-dimethyl-2,5-p-dioxanedione; the carbonate is 
1,3-dioxan-2-one; and the lactones are selected from the group consisting 
of .epsilon.-carprolactone and 1,4-dioxan-2-one. 
In a specific embodiment, the bioabsorbable component is manufactured from 
the monomers glycolide and 1,3-dioxan-2-one. In another specific 
embodiment, the nonabsorbable component is in the form of a knitted or 
woven sheet. 
Another alternative surgical composite structure for mammalian tissue has 
been invented. The structure comprises: 
a) a nonabsorable woven component prepared from a plurality of fibers, the 
fibers comprising a polymer selected from the group consisting of 
polytetrafluoroethylene, a copolymer of tetrafluoroethylene and 
hexafluoropropylene, perfluoroalkoxy resin, 
ethylene-chlorotrifluoroethylene copolymer, ethylene-tertafluoroethylene 
copolymer, and polyvinylidene fluoride, and 
b) a bioabsorbable component laminated to the nonabsorbable woven 
component, the bioabsorbable component comprising a polymer prepared from 
at least two monomers selected from the group consisting of lactides, 
carbonates and lactones. 
In one embodiment, the nonabsorbable woven component is selected from the 
group consisting of polytetrafluoroethylene, a copolymer of 
tetrafluoroethylene and hexafluoropropylene, and polyvinylidene fluoride. 
In a specific embodiment, the nonabsorbable woven component consists of a 
copolymer of tetrafluoroethylene and hexafluoropropylene. 
In another specific embodiment, the bioabsorbable component comprises a 
random copolymer. In a more specific embodiment, the random copolymer is 
prepared from at least the monomers glycolide and 1,3-dioxan-2-one. 
Yet another alternative surgical composite structure for mammalian tissue 
has been invented. The structure comprises: 
a) a nonabsorbable woven component prepared from a plurality of fibers, the 
fibers comprising a polymer selected from the group consisting of a 
polybutester and polybutylene terephthalate, and 
b) a bioabsorbable component laminated to the nonabsorbable woven 
component, the bioabsorbable component comprising a polymer prepared from 
at least two monomers selected from the group consisting of lactides, 
carbonates and lactones. 
In a specific embodiment, the nonabsorbable woven component is a 
polybutester. 
In another specific embodiment, the bioabsorbable component comprises a 
random copolymer. In a more specific embodiment, the random copolymer is 
prepared from at least the monomers glycolide and 1,3-dioxan-2-one. 
A drawing which describes the shape and/or geometrical configuration of the 
surgical composite structure is not necessary for an understanding of this 
invention. That is, any person skilled in the surgical composite structure 
art will know how to manufacture and how to use the invention by reading 
this specification, generally and the examples, specifically. 
It is to be understood that the bioabsorbable component can be coated onto 
the nonabsorbable reinforcing component by any coating means known in the 
prior art. The inventors have found that lamination is an adequate means 
for coating. Specifically, the inventors have found that bonding the 
bioabsorbable component to the nonabsorbable reinforcing component by 
fusion is an adequate means of laminating the two components. However, 
other forms of coating, such as encapsulation, are within the scope of 
this invention. 
Throughout this disclosure, it is to be understood that the term Teflon is 
a trademark of the E. I. DuPont and Company, DE, U.S.A., whether the term 
Teflon is or is not so identified as a trademark. 
The term fluoropolymer is generic and includes the terms fluoroplastic and 
fluoroelastomer. For a disclosure of fluoroplastics, see Modern Plastics 
Encyclopedia vol. 64 no. 10A (1987) pages 31-32, McGraw-Hill, N.Y., which 
is incorporated herein by reference. The Teflon.TM. FEP described in the 
examples is a copolymer of tetrafluoroethylene and hexafluoropropylene. It 
is also to be understood that the term polybutester as used in this 
disclosure is synonymous with the terms polyetherester, polyether-ester or 
polyether ester. A commercially available polybutester is the Hytrel.TM. 
(E. I. DuPont and Co.) copolymer.

Preferred embodiments of this invention are more fully described in the 
Examples 1 to 6, below. 
COMATIVE EXAMPLE A 
A woven mesh, identified as Style T-151-56 and supplied by Stern & Stern 
Textiles, Inc., Hugnet Fabrics Div., Hornell, N.Y. 14843, is used as a 
control for the composite meshes of Examples 1 and 2, below. It is made 
with monofilament fibers of Teflon.TM. FEP polymer with a diameter of 5 to 
6 mils (or 0.005 inch to 0.006 inch). These fibers are woven into a mesh 
configuration of approximately 80.times.90 strands per inch. The overall 
thickness of the woven fabric is approximately 12 mils (or 0.012 inch). 
EXAMPLE 1 
A composite structure consisting of a fabric of a woven mesh made up of 
biocompatible, nonabsorbable, monofilament fibers is encapsulated by 
lamination between two films of a bioabsorbable polymer. 
Specifically, the woven mesh is identified as Style T-151-56 and is 
supplied by Stern & Stern Textiles, Inc., Hugnet Fabrics Div., Hornell, 
N.Y. 14843. It is made with monofilament fibers of Teflon FEP polymer with 
a diameter of 5 to 6 mils (or 0.005 inch to 0.006 inch). These fibers are 
woven into a mesh configuration of approximately 80.times.90 strands per 
inch. The overall thickness of the woven fabric is approximately 12 mils 
(or 0.012 inch). 
The films of bioabsorbable polymer used in the laminated composite are 
prepared by compression molding a random copolymer of 50/50 weight percent 
of glycolide trimethylene carbonate to a thickness of approximately 10 
mils (or 0.010 inch) thick. The manufacture of the random copolymer is 
described, without the need for undue experimentation, in the prior art. 
See, e.g., the preparation of random copolymers described in U.S. Pat. No. 
3,736,646, which issued June 5, 1973 and U.S. Pat. No. 3,867,190 entitled 
"Reducing Capillarity of Polyglycolic Acid Sutures", which issued Feb. 18, 
1975, both patents being issued to E. Schmitt and M. Epstein and 
incorporated herein by reference. 
The conditions for molding these films is as follows. A pre-dried, 
preformed pellet of approximately 5.0 grams of the copolymer is placed 
between two 7 inch.times.7 inch caul plates and Teflon PTFE release film. 
This assembly is placed in a 6 inch.times.6 inch Carver Laboratory Press 
which is pre-heated to 145.degree. C..+-.5.degree. C. and gradually 
increased in pressure to 1,000 lbs. force on a 13/4 inch diameter ram. The 
pressure is held constant for 3 minutes. Subsequently, this assembly is 
removed from the press and cooled to approximately 15.degree. C. while 
still under press. The film is then easily released from between the 
Teflon release film. The resultant film is a transparent, amber-colored 
film of approximately mils (0.010 inch) thick .times.5 inches.times.5 
inches. 
The final composite structure is formed by laminating a film of the 
copolymer on either side of the Teflon FEP woven mesh between two 7 
inch.times.7 inch caul plates and Teflon PTFE release film. This assembly 
is placed in a 6 inch.times.6 inch Carver Laboratory Press which is 
pre-heated to 145.degree. C..+-.5.degree. C. and gradually increased in 
pressure to 1,000 lbs. force. The pressure is held constant for 
approximately 3 minutes. Subsequently, this assembly is removed from the 
press and cooled to approximately 15.degree. C. while still under 
pressure. The laminated composite structure is then easily released from 
between the Teflon PTFE release film. The resultant laminated composite 
consists of a Teflon FEP woven fabric which is completely encapsulated 
within the fused copolymer of 50/50 weight percent 
poly-(glycolide-co-trimethylene carbonate). The resultant laminated 
composite is approximately 20 mils (0.020 inch) thick and 5 inches.times.5 
inches in size. 
EXAMPLE 2 
A composite laminated structure is prepared similar to that described in 
Example 1 except the polymer films are made with a random copolymer of 
68/32 weight percent of glycolide trimethylene carbonate substituted for 
the 50/50 weight percent copolymer. The preparation of the random 
copolymer is described, without the need for undue experimentation, in the 
prior art. See, e.g., the preparation of random copolymers described in U. 
S. Pat. No. 3,736,646, which issued June 5, 1973 and U.S. Pat. No. 
3,867,190 entitled "Reducing Capillarity of Polyglycolic Acid Sutures", 
which issued Feb. 18, 1975, both patents being issued to E. Schmitt and M. 
Epstein and incorporated herein by reference. Also, the processing 
temperature was increased to approximately 150.degree. C..+-.5.degree. C. 
EXAMPLE 3 
A composite laminated structure is prepared similar to that described in 
Example 2 except that the woven mesh is made from monofilament fibers of 
HYTREL.RTM. with a diameter of 5 to 6 mils (0.005 inch to 0.006 inch). 
Hytrel.TM. (E. I. DuPont and Co.) is a polyether-ester, and can be a 
polymer of polytetramethylene glycol with terephthalic acid and 1,4 
-butanediol. These fibers are woven into a mesh configuration of 
approximately 80.times.90 strands per inch. The overall thickness of the 
woven fabric is approximately 12 mils (0.012 inch). 
EXAMPLE 4 
Sterile, composite structure samples of the type described in Example 1 
were implanted in 3 rats to determine the initial efficacy of this 
composite structure. 
At 6 weeks following implantation the composite structure seemed to be 
associated with much inflammation. At 6 months this did not appear to be 
the case, and the Teflon FEP mesh component of the composite structure was 
well-encased in the animal subcutaneous tissues. 
EXAMPLE 5 
Sterile, composite structure samples of the type described in Comparative 
Example A and Example 1 were implanted in 36 rats. Each wound area was 
infected by the introduction of staphylococcus aureus, E. coli, and 
bacteriodes in a mixture of 10.sup.5 organisms per milliliter. 
Thirty-two of the 36 rats implanted with the uncoated Teflon FEP woven mesh 
of Comparative Example A showed clinical signs of infection. All of these 
results were confirmed histologically. Many white cells were found around 
the abscess cavity. These were cultured positive for mixtures of organisms 
which were implanted during the operative placement of the Comparative 
Example A uncoated Teflon FEP woven mesh. 
After 6 months implantation the results indicated that 35 out of the 36 
rats were free of infection with implants of the composite structure of 
Example 1. 
EXAMPLE 6 
An additional in vivo study was conducted to confirm the advantages of a 
tissue reinforcing woven mesh made from fibers of a nonabsorbable polymer 
encapsulated or coated with an absorbable polymer, versus an uncoated 
mesh, in an infected wound area. 
Both sterile, composite structure samples of the type described in Example 
2 and uncoated Teflon FEP woven mesh samples described in Comparative 
Example A were implanted in 18 rabbits. Each animal was implanted with two 
(2) samples of coated mesh and two (2) samples of uncoated mesh diagonally 
on shoulder/hip quadrants. Each wound area was infected as described in 
Example 5, above. 
The results of this study indicated that there was no infection in the 
areas of the composite structure samples at the end of 6 weeks. In the 
uncoated Teflon FEP woven mesh wounds all were found to be infected after 
6 weeks. 
EXAMPLE 7 
An in vivo study was conducted in dogs to investigate the effectiveness of 
a composite structure of the type described in Example 2 in a model more 
closely resembling the intended commercial use of the material. 
Fourteen mongrel dogs were anesthetized and their abdomens were prepared 
using sterile solutions. Using a midline incision, two-thirds of the left 
rectus muscle was resected. In eight animals the resected muscle was 
replaced with uncoated teflong FEP woven mesh (comparative Example A), 
which was sewn in place using a running polypropylene (PROLENE1/2) suture. 
In six animals, coated mesh (Example 2) was used to replace the resected 
muscle. 
All wounds were contaminated with 1 ml of 10.sup.6 org/ml concentrations of 
staph aureus and E. Coli from human blood isolates. Wounds were closed 
using stainless steel clips, no antibiotics were given. The temperatures 
of the animals were recorded daily for two weeks post-operatively. In all 
cases a sustained elevated temperature was observed, indicating a viable 
contamination. In each case, some animals were sacrificed at three months 
for histological examination of the meshes, the remainder being sacrificed 
after six months of post-operative follow-up. One of the animals with an 
uncoated mesh implant died of peritonitus prior to the three month 
interval. 
In the three month sacrifice group implantation of the uncoated Teflon mesh 
resulted in seven out of seven animals manifested draining infected 
wounds. No exposed mesh was observed, although two small bowel-mesh 
fistulas were noted. No hernia formation was observed, although the 
general condition of the animals were considered to be "unhealthy". Three 
animals were maintained for six months, at which time the condition of the 
wounds was unchanged, i.e. draining of infected material from the incision 
site. 
In the three month sacrifice group implantation of the coated Teflon mesh 
resulted in six out of six animals had wound drainage. Four animals 
demonstrated mesh rejection and exposure (three of these were sacrificed 
for histological study), and one animal exhibited a small bowel-mesh 
fistula. After six months one out of the remaining three animals continued 
to exhibit mesh rejection and exposure. 
EXAMPLE 8 
A concurrent in vivo study to that described in Example 7 was conducted 
using identical surgical methods. In this study, six animals were 
implanted with an uncoated HYTREL.RTM. fiber mesh as described in Example 
3. Also, six animals received the coated HYTREL.RTM. fiber mesh described 
in Example 3. The progress of the animals was followed in the same way as 
described in Example 7. 
After three months implantation of the uncoated HYTREL.RTM. mesh, five out 
of six animals exhibited draining wounds. After six months, two out of 
three animals demonstrated wound drainage. No other complications were 
observed. 
After three months implantation of the coated HYTREL.RTM. mesh, none of the 
animals exhibited wound drainage. After six months one animal of three 
developed a small amount of drainage due to a piece of the polypropylene 
suture which had poked through the wound incision. This had occurred after 
four months implantation. The mesh itself was not exposed and resection of 
the suture resulted in healing of the site in excess of 2 months. The 
overall condition of these animals at sacrifice was observed to be good. 
Three additional animals were implanted with coated HYTREL.RTM. mesh 
samples, but were not intentionally contaminated. At three months none of 
the animals exhibited any complications; at this time one animal was 
sacrificed for histological examination. No complications were observed at 
six months for the two remaining animals. 
EXAMPLE 9 
Three animals from the study in Example 7 that had received coated Teflon 
FEP mesh implant and that had become chronically infected and had 
developed rejection and exposure of the mesh at the three month period 
were used as subjects in an additional clinically relevant study. These 
animals were treated by resection of the infected mesh, replacement of 
that infected mesh was with the coated HYTREL.RTM. mesh used in Example 8, 
and three doses of strep/pen antibiotics were administered. After three 
months two of the animals wounds had healed. The third animal had died of 
an intraoperative anesthetic death. 
EXAMPLE 10 
Four puppies with spontaneously occurring (congenital) umbilical hernias 
were used for an in vivo evaluation of the coated HYTREL.RTM. mesh (from 
Examples 3 and 8) for hernia repair, and its effects during growth into an 
adult dog. 
The puppies abdomens were prepped in a sterile manner while under 
anesthesia and a midline incision was made over the hernia. Entry into the 
hernia was not complicated by enterotomy although the muscle and falciform 
ligament was resected in each animal along with the sack for adequate 
exposure. No antibiotics or contaminants were administered. Coated 
HYTREL.RTM. mesh was used to replace the resected hernias in all four 
animals in order to achieve abdominal wall closure. 
All four animals grew to normal adulthood (1 year old). No evidence of 
complications (i.e. obstruction, infection, fistula or impairment of the 
animal activity) was observed over the course of the study.