Synthetic absorbable surgical devices of poly(alkylene oxalates)

Synthetic filaments composed of homopolymers and copolymers of poly(alkylene oxalates) are absorbable in animal tissue with minimal adverse tissue reaction. Polymers prepared by reacting a dialkyl oxalate with an alkylene diol are melt spun and drawn to obtain oriented fibers having good tensile properties and a high level of flexibility and softness. The filaments are particularly useful in the preparation of surgical prosthesis comprising woven or knitted fabrics and meshes. Other absorbable surgical devices including films and molded items may also be prepared from the disclosed polymer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to synthetic absorbable devices, and more 
particularly, to synthetic absorbable filaments comprising extruded and 
oriented polymers of poly(alkylene oxalates). 
2. Description of Prior Art 
Absorbable filamentary materials have traditionally been comprised of 
natural collagenous materials obtained from sheep or beef intestine, 
commonly known as catgut. More recently, it has been proposed to 
manufacture synthetic absorbable fibers from polyesters of 
hydroxycarboxylic acids, notably polylactide, polyglycolide, and 
copolymers of lactide and glycolide. Such synthetic absorbable products 
are described in U.S. Pat. Nos. 3,636,956, 3,297,033, and elsewhere in the 
literature. Polyesters of succinic acid have also been suggested for at 
least partially bioresorbable surgical articles as disclosed, for example, 
in U.S. Pat. No. 3,883,901. 
The present invention provides for polymers of poly(alkylene oxalate) to be 
melt extruded into pliable, monofilament fibers having a high level of 
softness and flexibility and which are absorbable in animal tissue without 
significant adverse tissue reaction. The fibers have good initial tensile 
and knot strength and can be sterilized with cobalt-60 without serious 
loss of these properties. The higher alkylene oxalate polymes have good in 
vivo strength retention and are absorbed slowly while the lower alkylene 
oxalate polymers are characterized by rapid absorption. 
Polymers of poly(alkylene oxalates) and the preparation thereof are 
described in the art. Carothers et al, J. Amer. Chem.. Soc. 52, 
3292(1930), for example, describes the ester interchange reaction of diols 
such as ethylene glycol, 1,3-propanediol, or 1,4-butanediol with diethyl 
oxalate to yield a mixture of monomer, soluble polymer and insoluble 
polymer. The reaction of oxalic acid and an alkylene glycol to form 
polyester resins is described in U.S. Pat. No. 2,111,762, while the 
preparation of polyesters of fiber-forming quality from dicarboxylic acids 
and diols is described in U.S. Pat. No. 2,952,652. Superpolyesters of 
fiber-forming quality and derived from dibasic acids plus glycols are 
described in U.S. Pat. Nos. 2,071,250 and '251. Linear polyesters of 
oxalic acid have been reported as having high melting points, being 
soluble in many solvents, capable of forming films, and readily hydrolyzed 
[Savinov et al, Polymer Science USSR 6, 1475 (1964)]. 
The absorbability of poly(alkylene oxalate) polymers in animal tissue has 
not been known prior to the present invention, and there has been no 
suggestion in the art for the use of poly(alkylene oxalate) polymers in 
surgical applications. In particular, there has been no suggestion in the 
art that absorbable fibers having good tensile properties could be 
prepared from poly(alkylene oxalate) polymers or that such fibers would 
have any useful application in the fabrication of surgical devices. 
It is accordingly an object of the present invention to provide new and 
useful articles of poly(alkylene oxalate) polymers. A further object of 
this invention is to provide synthetic absorbable filaments of 
poly(alkylene oxalate). It is yet a further object of this invention to 
provide absorbable surgical aids and prostheses fabricated of fibers or 
cast or machined from blocks of poly(alkylene oxalate) polymers. 
SUMMARY 
Synthetic absorbable filaments and other surgical aids are prepared from 
poly(alkylene oxalate) polymers having the formula: 
##STR1## 
wherein R is C.sub.3 to C.sub.16 alkylene and n is the degree of 
polymerization resulting in a fiber-forming polymer having an inherent 
viscosity (as hereinafter defined) of at least about 0.4. 
Polymers prepared by the transesterification reaction of an alkylene diol 
and diethyl oxalate are melt extruded into filaments suitable for use in 
the fabrication of surgical aids. The filaments are characterized by high 
tensile and knot strength with a high degree of softness and flexibility 
as characterized by a Young's modulus of less than about 600,000.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Polymers of the present invention are comrised of units having the general 
formula: 
##STR2## 
wherein R is a C.sub.3 to C.sub.16 alkylene, most preferably C.sub.4 to 
C.sub.10 alkylene, and n is the degree of poymerization resulting in a 
fiber-forming polymer and preferably in a polymer having an inherent 
viscosity of at least about 0.4 as determined at 25.degree. C. on a 0.1 
percent solution of polymer in chloroform or hexafluoroisopropanol (HFIP). 
Alkylene oxalate polymers of the present invention are conveniently 
prepared by an ester interchange reaction between an lkylene diol and a 
lower ester of oxalic acid in the presence of an ester interchange 
catalyst. The diol is preferably a C.sub.3 C.sub.16 alkylene diol, and the 
ester of oxalic acid preferably diethyl oxalate. The ester interchange is 
preferably conducted in two stages wherein the reactants are first heated 
with stirring under a nitrogen atmosphere to form a prepolymer with the 
removal of ethanol, followed by postpolymerization under heat and reduced 
pressure to obtain a final polymer of the required molecular weight. 
The polymer is melt extruded through a spinnerett in a conventional manner 
to form one or more filaments which are subsequently drawn about 4X to 6X 
in order to achieve molecular orientation and improve tensile properties. 
The resulting oriented filaments are characterized by a straight tensile 
strength of at least 30,000 psi and a crystallinity of at least about 15 
percent. 
To further improve dimensional stability and in vivo strength retention, 
the oriented filaments may be subjected to an annealing treatment. This 
optional annealing treatment consists of heating the filaments to a 
temperature of from about 40.degree. to 80.degree. C., most preferably 
from about 40.degree. to 60.degree. C. while restraining the filaments to 
prevent any substantial shrinkage. The filaments are held at the annealing 
temperature for a few seconds to several days or longer depending on the 
temperature and processing conditions. In general, annealing at 40.degree. 
to 60.degree. C. for up to about 24 hours is satisfactory for 
poly(alkylene oxalate). Optimum annealing time and temperature for maximum 
improvement in fiber in vivo strength retention and dimensional stability 
is readily determined by simple experimentation for each particular fiber 
composition. 
The preparation of high molecular weight oriented filaments of 
poly(alkylene oxalate) is further illustrated by the following examples 
where all percentages are by weight unless otherwise noted. The following 
analytical methods were used to obtain the data reported in the examples. 
Inherent viscosity (N.sub.inh) was determined at 25.degree. C. on a 0.1 
percent solution of polymer in chloroform or hexafluoriosopropanol (HFIP). 
The infrared spectra of polymer films (cast from CHCl.sub.3 or HFIP) were 
recorded on a Beckman Acculab 1 spectrophotometer. The NMR spctra of the 
polymer solutions in CDCl.sub.3 were recorded on an MH-100 or CFT-20 
spctrometer. A DuPont 990 DSC apparatus was used to record the glass 
transition (T.sub.g), crystallization (T.sub.c) and melting temperatures 
(T.sub.m) of the polymers in nitrogen, using 4 mg samples and a heating 
rate of 10.degree. C./min or as otherwise specified. The thermogravimetric 
analysis (TGA) data of the polymers were recorded in nitrogen using a 
DuPont 950 TGA apparatus at a heating rate of 10.degree. C./min and with 
10 mg samples. A Philips vertical goniometer with graphite crystal 
monochromatized copper K.alpha.-radiation was used to obtain the X-ray 
powder and fiber diffraction patterns of the polymers. Crystallinity was 
determined by the method of Hermans and Weidinger and the diffractometer 
patterns were resolved with a DuPont 310 curve analyzer. 
In vitro hydrolyses of polymer discs (about 1.2 g, 2.2 cm diameter) and 
monofilaments (8-25 mil) were conducted in a phosphate buffer of pH 7.25 
at 37.degree. C. 
In vivo absorption (muscle) was determined by implanting two 2 cm segments 
of monofilament fiber into the left gluteal muscles of female Long-Evans 
rats. The implant sites were recovered after periods of 60, 90, and 120 
and 180 days and examined microscopically to determine the extent of 
absorption. In vivo absorption (subcutaneous) is a nonhistological 
technique in which continuous observation of the biological degradation of 
segmens of the filament were made by implanting two filaments, 2 cm long, 
into the abdominal subcutis of young female rats. The implants are readily 
visible when the skin is wetted with propylene glycol and extent of 
absorption can be determined by subjective visual examination. 
In vivo strength retention was determined by implanting segments of 
filaments in the posterior dorsal subcutis of female Long-Evans rats for a 
period of 5 to 30 days. The samples were recovered at the designated 
periods and pull-tested for straight tensile strength. 
EXAMPLES 
General Polymerization Procedure 
Diethyl oxalate was heated with a selected diol in a stirred reactor using 
a stannous alkanoate or oxalate or an organic titanate as a catalyst. The 
reaction was conducted uner a nitrogen atmosphere at suitable temperatures 
until a substantial portion of the calculated amont of ethanol was 
obtained. Postpolymerization of the resulting prepolymer was then 
continued under reduced pressure using a suitable heating scheme. At the 
end of the postpolymerization period, the molten polymer was allowed to 
cool slowly at room temperature, isolated, ground and redried at 
25.degree.;0 to 80.degree. C. (depending on the polymer T.sub.m) in vacuo 
for at least one day. Detailed experimental conditions for the preparation 
of representative samples of linear polyalkylene oxalates and important 
properties of the resulting polymers are presented below. 
EXAMPLE 1 
Poly(trimethylene oxalate) 
Distilled 1,3-propanediol (17.48 g, 0.23 mole) and diethyl oxalate (29.2 g, 
0.2 mole) were mixed with a catalytic amount of stannous oxalate (4.1 mg, 
0.02 mmole) under nitrogen. The mixture was heated with stirring while 
allowing the resulting ethanol to distill at 150.degree., 120.degree. and 
150.degree. C. for 0.5, 2 and 4 hours, respectively. The resulting polymer 
was then cooled to about 100.degree. C. and the pressure was reduced to 
0.1 mm. The polymerization was continued in vacuo at 150.degree., 
160.degree., 180.degree. and 200.degree. C. for 1, 3, 1 and 2 hours, 
respectively. The polymeric product was recovered as a clear, soft 
material. 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.57; 
Dsc (20.degree. c./min): T.sub.g = -1.degree. C. 
EXAMPLE 2 
Poly(tetramethylene oxalate) 
Diethyl oxalate (36.5 g, 0.25 mole) was mixed with 1,4-butanediol (45 g, 
0.5 mole) and a 1 percent solution of tetrakis(2-ethylhexyl) titanate 
(TOT) catalyst (1 ml, 0.012 mmole) and transferred to a resin kettle under 
a dry nitrogen atmosphere. A prepolymer was formed by heating the reaction 
mixture under a nitrogen atmosphere for 2 hours each at 140.degree. and 
160.degree. C. while allowing the formed ethanol to distill. The mixture 
was then heated under reduced pressure (2-3 mm Hg) at 160.degree. and 
180.degree. C. for 20 and 2 hours, respectively. The polymer melt was 
slow-cooled, quenched in liquid nitrogen, isolated and ground. The ground 
polymer was redried at room temperature, in vacuo. 
Polymer Characterization 
N.sub.inh in HFIP = 0.95 
Dsc (20.degree. c./min): T.sub.g = 4.5; T.sub.c = 22; T.sub.m = 105.degree. 
C. 
Polymer Melt-Spinning and Fiber Properties 
The polymer was spun using an Instron Rheometer at 110.degree. C. with a 30 
mil die and a shear rate of 841 sec.sup.-1. The extrudates were quenched 
in ice water, wound and dried in vacuo at 25.degree. C. The fibers were 
drawn 5X at 32.degree. C. and the properties of the drawn fibers were as 
follows: 
Inherent viscosity in HFIP: 0.79 
DSC data (10.degree. C./min): T.sub.g = 15; T.sub.m = 103.degree. C. 
X-ray data: 50% crystallinity 
Physical properties: 
Fiber diameter = 12.9 mil 
Straight tensile strength = 34,500 psi 
Elongation = 39% 
Modulus = 2.19 + 10.sup.5 psi 
In vivo properties: After 5 days of implantation in rat muscle, the initial 
tensile strength of the fiber was reduced from 4.0 lbs to zero. 
Subcutaneous implantation of the fibers in rats indicates that 50 percent 
of their apparent mass was absorbed in the first 9 days, and 10 percent 
remained after 15 days, and absorption was substantially complete after 28 
days. 
In vitro hydrolysis data: Drawn fibers lost 67 percent of their initial 
mass in 7 days. 
EXAMPLE 3 
Poly(hexamethylene oxalate) 
Distilled diethyl oxalate (73.1 g, 0.500 mole) was mixed with 
1,6-hexanediol (61.2 g, 0.519 mole) and stannous octoate catalyst (0.33 M 
in toluene; 0.3 ml, 0.1 mmole) under a dry nitrogen atmosphere in a glass 
reactor equipped with a mechanical stirrer. A prepolymer was formed by 
heating the mixture at 120.degree. C. for 2 hours and then at 160.degree. 
C. for 3 hours under nitrogen at 1 atmosphere while allowing the formed 
ethanol to distill. The prepolymer was then heated for one hour in vacuo 
(0.1 mm Hg) at 80.degree. and then 90.degree. C. the postpolymerization of 
the polymer melt was completed by heating at 100.degree., 115.degree., 
135.degree., 150.degree., 170.degree., 190.degree. and 200.degree. C. for 
2, 1, 1.5, 4, 6, 1 and 6.5 hours, respectively. The polymer was allowed to 
cool at room temperature, quenched in liquid nitrogen, isolated and 
ground. The ground polymer was dried in vacuo at room temperature. 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.83 
Dsc (10.degree. c./min): T.sub.m = 70.degree. C. 
Polymer Melt-Spinning and Fiber Properties 
The polymer was spun using an Instron Rheometer at 105.degree. C. with a 40 
mil die. The extrudates were quenched in ice water, wound and dried in 
vacuo. The fibers were drawn 5X at room temperaure and the properties of 
the drawn fibers were as follows: 
X-ray date: 47% crystallinity 
Physical properties: 
Fiber diameter = 8.7 mils 
Straight tensile strength = 5.22 .times. 10.sup.4 psi 
Knot strength = 3.70 .times. 10.sup.4 psi 
Elongation = 33% 
Modulus = 1.89 .times. 10.sup.5 psi 
In vivo evaluation: After 3 days of implantation in the rat muscle, drawn 
fibers retained 35 percent of their original strength. No measurable 
strength was recorded after 7 days of implantation. After 42 days, 
absorption of the fiber was about 20 percent complete and after 121 days 
absorption was substantially complete. 
In vitro hydrolysis data: Drawn fibers lost 83 percent of their initial 
mass in 31 days. 
EXAMPLE 4 
Poly (octamethylene oxalate) 
Using a similar system to that of Example 3, distilled diethyl oxalate 
(109.6 g, 0.750 mole), distilled 1,8-octanediol (113.6 g, 0.777 mole) and 
stannous octoate catalyst (0.33 M in toluene - 0.455 ml, 0.150 mmole) were 
mixed under a dry nitrogen atmosphere in a glass reactor equipped with a 
mechanical stirrer. A prepolymer was formed by heating the mixture at 
120.degree. C. for 12 hours under nitrogen while allowing the formed 
ethanol to distill. Prior to postpolymerization, the product was heated 
for 1 hour at 90.degree. C. and 0.1 mm Hg. The postpolymerization of the 
stirred polymer melt was completed by heating at 110.degree., 135.degree., 
150.degree., 170.degree. and 200.degree. C. for 3.5, 2.5, 4.5, 0.5 and 5 
hours, respectively at 0.1 mm Hg. The polymer was cooled, quenched in 
liquid nitrogen, isolated, ground and dried in vacuo at room temperature. 
The polymer was then heated at 60.degree. C. in vacuo for one hour and 
finally at 200.degree. C. for 6 hours to yield the final product. 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.88 
Dsc (10.degree. c./min): T.sub.m = 75.degree. C. 
Polymer Melt-Spinning and Fiber Properties 
The polymer was spun according to the procedure described in Example 3. The 
extrudates were quenched in an ice water bath and subsequently drawn 6X at 
64.degree. C. The properties of the drawn fibers were as follows: 
Inherent viscosity in CHCl.sub.3 : 0.8 
X-ray data: 54% crystallinity 
Physical properties: 
Fiber diameter = 8.8 mil 
Straight tensile strength = 4.99 .times. 10.sup.4 psi 
Knot tensile strength = 3.95 .times. 10.sup.4 psi 
Elongation = 32% 
Modulus = 1.81 .times. 10.sup.5 psi 
Dsc (10.degree. c./min): T.sub.m = 75.degree. C. 
In vitro hydrolysis data: The drawn monofilaments lost, 15, 66 and 96 
percent of their original weight after 18, 122 and 199 days respectively. 
In vivo evalulation: Drawn monofilaments implanted in the posterior dorsal 
subcutis retained 79, 19 and 0 percent of their original breaking strength 
(3.16 lbs) after 3, 7 and 14 days, respectively. Fibers implanted into the 
gluteal muscles of rats to determine their absorption and tissue response 
characteristics at 3, 21, 42 and 119 days postimplantation showed no 
absorption up to the 42-day period. At the 119-day period, there was 
evidence of minimal absorption of some of the fibers. 
EXAMPLE 5 
Poly(decamethylene oxalate) 
1,10-Decanediol (87.1 g, 0.5 mole) was mixed with diethyl oxalate (58.4 g, 
0.4 mole) and a solution of TOT catalyst in toluene (0.012 mmole) under a 
nitrogen atmosphere. The reaction mixture was heated with stirring while 
allowing the resulting ethanol to distill at 120.degree., 130.degree. and 
140.degree. C for 4, 2.5 and 2 hours respectively. The pressure was then 
reduced to 0.5 mm while heating to 190.degree. C. for 20 minutes. The 
polymerization was continued in vacuo at 190.degree. and 210.degree. C. 
for 4 and 13 hours, respectively. The polymer was recovered and 
characterized as follows: 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.45 
Dsc (10.degree. c./min): T.sub.m = 77.5.degree. C. 
Polymer Extrusion and Fiber Properties 
The polymer was extruded at 84.degree. C. using a 40 mil die. The resulting 
undrawn monofilament had an average diameter of 19 mil. 
In vitro hydrolysis data: 
The undrawn monofilaments had a weight loss of 1, 11, 38 and 62 percent 
after 6, 17, 44 and 177 days, respectively. 
EXAMPLE 6 
Poly(dodecamethylene oxalate) 
Distilled diethyl oxalate (14.6 g, 0.100 mole) was mixed with 
1,12-dodecanediol (20.8 g, 0.103 mole) and stannous octoate catalyst (0.33 
M in toluene -- 0.061 ml, 0.02 mmole) under a dry nitrogen atmosphere in a 
glass reactor equipped for magnetic stirring. The prepolymer was formed 
after heating the mixture at 120.degree. C. for 3 hours and 160.degree. C. 
for 2 hours under nitrogen at 1 atmosphere while allowing the formed 
ethanol to distill. The mixture was then heated for 6 hours in vacuo (0.1 
mm Hg) at 200.degree. C. and then 210.degree. C. for 2 hours. The 
postpolymerization of the polymer melt was completed after heating at 
200.degree. C. for 5 additional hours. The polymer was cooled at room 
temperature and recovered. 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.57 
Dsc (20.degree. c./min): T.sub.m = 91.degree. C. 
EXAMPLE 7 
Poly(hexadecamethylene oxalate) 
Using a similar system to that used for Example 6, diethyl oxalate (8.0 g, 
0.055 mole), 1,16-hexadecanediol (14.6 g, 0.057 mole) and stannous octoate 
catalyst (0.33 M in toluene -- 0.033 ml, 0.01 mmole) were mixed under an 
atmosphere of dry nitrogen in a glass reactor equipped for magnetic 
stirring. The prepolymer was formed after heating the mixture at 
120.degree. C. for 3 hours and then at 160.degree. C. for 2 hours under 
nitrogen at 1 atmosphere while allowing the formed ethanol to distill. The 
mixture was then heated in vacuo at 0.1 mm Hg and at 200.degree., 
210.degree. and 230.degree. C. for 2, 2 and 3 hours, respectively. The 
postpolymerization of the stirred polymer melt was completed after heating 
at 200.degree. C. for 4 additional hours. The polymer was cooled and 
recovered. 
Polymer Characterization 
N.sub.inh in CHCl.sub.3 = 0.45 
Dsc (20.degree. c./min): T.sub.m = 95.degree. C., T.sub.g = 40.degree. C. 
While the preceding examples have been directed to the preparation of 
specific homopolymers of poly(alkylene oxalates), these examples are for 
purposes of illustration only and are not limiting of the invention. 
Copolymers of C.sub.3 to C.sub.16 alkylene oxalate with up to about 50 
percent by weight of one or more other compatible monomers which produce 
nontoxic and absorbable polymers, and physical mixtures of homopolymers 
and copolymers, are likewise included within the present invention. 
It is to be understood that inert additives such as coloring materials and 
plasticizers can be incorporated in the polymers of the present invention. 
Any of a variety of plasticizers such as, for instance, glyceryl 
triacetate, ethyl benzoate, diethyl phthalate, dibutyl phthalate and 
bis-2-methoxyethyl phthalate can be used if desired. The amount of 
plasticizer may vary from 1 to about 20 percent or more based on the 
weight of the polymer. Not only does the plasticizer render the filaments 
even more pliable, but it also serves as a processing aid in extrusion and 
thread preparation. As used herein, the term "inert" means materials that 
are chemically inert to the polymer, and biologically inert to living 
tissue, i.e., do not cause any of the adverse effects previously 
discussed. 
Filaments of the present invention are adversely affected by moisture and 
are accordingly preferably packaged dry in a substantially moisture-free 
environment within a hermetically sealed package. A suitable package is 
fabricated of two sheets of aluminum foil or an aluminum foil-plastic 
laminate heat sealed or bonded with adhesive around the border of package 
to hermetically seal the cavity and isolate the contents of the package 
from the external atmosphere. The package may be evacuated or filled with 
a dry, inert gas such as air or nitrogen. Such packages are conventionally 
used for storing hydrolytically sensitive materials comprised of polymers 
of glycolide and/or lactide as illustrated, for example, in U.S. Pat. No. 
3,636,956. 
Filaments of the present invention may be used as monofilaments or 
multifilaments and may be woven, braided, or knitted alone or in 
combination with other absorbable fibers such as polyglycolide or 
poly(lactide-co-glycolide), or in combination with nonabsorbable fibers 
such as nylon, polypropylene, polyethylene-terephthalate, or 
polytetrafluoroethylene to form surgical fabrics and tubular structures 
having use in the repair of arteries, veins, ducts, esophagi and the like. 
Those filaments which have an initial straight tensile strength and knot 
strength of at least 40,000 psi and 30,000 psi respectively, retain a 
substantial portion of their initial tensile strength after 21 days in 
vivo, and are substantially completely absorbed in vivo within about 6 
months, are also useful as synthetic absorbable sutures. 
Multifilament yarns constructed of the poly(alkylene oxalate) filaments of 
the present invention together with nonabsorbable filaments are useful in 
the fabrication of surgical fabrics which are only partially absorbable 
for applications where long-term fabric strength retention is desirable 
even after the absorbable components have been replaced by natural tissue 
growth into the fabric. The relative proportions of absorbable filaments 
and nonabsorbable filaments may be varied to obtain the absorption and 
strength retention characteristics desired in the particular fabric or 
tubular implant. 
Composite fabrics of absorbable and nonabsorbable materials may be 
fabricated by conventional textile processes such as weaving, knitting and 
nonwoven felting as described in U.S. Pat. Nos. 3,108,357 and 3,463,158. 
Methods of weaving and crimping tubular vascular prostheses are described 
in U.S. Pat. No. 3,096,560. In addition, surgical aids may be composed of 
"bi-component filaments" of absorbable and nonabsorbable components as 
described in U.S. Pat. No. 3,463,158, the teaching of which is 
incorporated herein by reference. 
Fabrics containing filaments of the present invention are useful in 
surgical applications where an absorbable aid or support is required, as 
for example, in hernia repair and in supporting damaged liver, kidney and 
other internal organs where a temporary aid during healing is needed. 
The polymers of the present invention are also useful in the manufacture of 
cast films and other solid surgical aids such as scleral buckling 
prostheses. Thus, absorbable cylindrical pins, screws, reinforcing plates, 
and the like may be machined from the cast polymer. 
Many additional embodiments of this invention will be apparent to those 
skilled in the art and may be made without departing from the spirit and 
scope thereof. It is accordingly understood that this invention is not 
limited to the specific embodiments thereof except as defined in the 
appended claims.