Areal implant

An areal implant, in particular for abdominal wall closure, has a flexible basic structure made from a knitted fabric comprising non-resorbable or slowly resorbable material or a combination of such materials. The knitted fabric of the basic structure is designed to stretch more than the tissue region destined to receive the implant below a critical force and stretch less than this tissue region above the critical force. The critical force lies below the highest load which is allowable for this tissue region. The basic structure is provided with a stiffening, synthetic resorbable material whose resorption time is less than that of the basic structure.

FIELD OF THE INVENTION 
The invention relates to an areal implant, in particular for abdominal wall 
closure. 
BACKGROUND OF THE INVENTION 
During an operation in the abdominal region, it is often necessary to 
strengthen the abdominal wall using an inserted areal implant. It is known 
to use nets made from the non-resorbable plastics polypropylene or 
polyester or from the slowly resorbable polyglactin 910 (a copolymer of 
glycolide and lactide in the ratio 9:1) for such implants. Metallic 
implants are also used. 
The known implant nets have some disadvantages. For example, they are 
relatively heavy, i.e. the areal weight is as a rule more than 50 
g/m.sup.2 and predominantly even ca. 100 g/m.sup.2. If the implants are 
not resorbable, a relatively large quantity of foreign substance thus 
remains permanently in the body. In terms of tearing strength, the known 
implant nets are frequently over-sized, i.e. they have a much higher 
strength than is required from a physiological viewpoint. These 
properties, combined with the usual, net-like construction of the basic 
structure of the previously known implants, can mean that the well-being 
and the mobility of a patient who is fitted with such an implant are 
limited. 
Another disadvantage of the previously known areal implants is that, 
although they conform better to the abdominal wall after the operation if 
they are more flexible, they can then only be inserted with difficulty, 
since e.g. they fold readily. On the other hand, although a rigid implant 
is easy to handle, it can lead to problems in the long term after 
insertion into the abdominal wall, as already mentioned. The previously 
known areal implants are thus either too flexible for ease of working 
during an operation or too rigid for an unproblematical interaction with 
the abdominal wall into which they are inserted. 
SUMMARY OF THE INVENTION 
It is thus the object of the invention to provide an areal implant, in 
particular for abdominal wall closure, which can be worked easily during 
an operation and which shows an elasticity behavior in the long term which 
is matched to the tissue into which it is inserted. 
This object is achieved by an areal implant, in particular for abdominal 
wall closure, having the features of claim 1. Advantageous embodiments 
result from the dependent claims.

DETAILED DESCRIPTION OF THE INVENTION 
The areal implant according to the invention has a flexible basic structure 
made from a knitted fabric comprising non-resorbable material or 
resorbable material or a combination of such materials. If resorbable 
material is used, the resorption time (i.e. the period after which the 
total mass of the implant has degraded in vivo) is at least 60 days, 
and/or the in vivo decrease in strength is so slow that 30 days after 
implantation the tearing strength is still at least 10% of the initial 
tearing strength. Non-resorbable or slowly resorbable materials are used 
in order that the basic structure is stable in the longer term and a more 
certain healing success can be ensured. 
The term "knitted fabric" is to be understood here in the widest sense. It 
also includes, for example, knits and other mesh structures, i.e. 
essentially all textile materials which are not pure woven fabrics. 
The knitted fabric of the basic structure is designed to stretch more than 
the tissue region destined to receive the implant below a critical force 
and stretch less than this tissue region above the critical force. The 
critical force is below the highest load this tissue region can be 
submitted to. The flexible,basic structure is thereby matched without 
problems to the usual movements of the tissue (e.g. of an abdominal wall) 
into which the areal implant is inserted or sewn. In the case of small 
forces, as occur during normal movements by the patient, the elasticity 
behavior of the system consisting of an abdominal wall and the inserted 
implant is shaped by the abdominal wall. The implant thus does not act as 
a foreign body. If, on the other hand, the forces exceed the critical 
force, the implant absorbs the forces and thus prevents injury to the body 
tissue, e.g. the abdominal wall. 
According to the invention, the basic structure is stiffened by a synthetic 
resorbable material whose resorption time is less than that of the basic 
structure and preferably lies in the range from 2 days to 200 days. As a 
result, the areal implant is relatively firm and easy to handle during the 
operation (e.g. when cutting to size and inserting) but loses its then 
undesired rigidity after a relatively short time in the body tissue, 
because the stiffening synthetic material is resorbed. 
In a preferred version, the knitted fabric of the basic structure is 
constructed in such a way that it has stress/strain properties which can 
be quantified using a plunger pressing test, as stated in claim 2. 
The areal weight of the basic structure is preferably less than 50 
g/m.sup.2. When suitable materials are used (see below), for an implant 
for abdominal wall closure of correspondingly low mass, a strength can be 
achieved which lies above the physiological framework data given by Klinge 
(U. Klinge, B. Klosterhalten, W. Limberg, A. P. Ottinger, V. Schumpelick: 
Use of mesh materials in scar rupture; Change in the abdominal wall 
dynamics after mesh implantation; Poster, 162nd Convention of the Lower 
RhineWestphalian Surgeon's Association, 1995). According to him, the 
intra-abdominal pressure is 20 kPa (150 mm Hg) at most, the wall stress at 
the edge of an abdominal tissue region 16 N/cm at most and the tearing 
strength of the fasciae, 20 N/cm to 30 N/cm. An implant constructed in 
this way is thus able to absorb all forces occurring physiologically at a 
healthy abdominal wall and also offers an additional safety reserve. More 
stable and thus heavier basic structures offer no additional advantage, 
but can have the disadvantage of undesired rigidity mentioned at the 
beginning. 
The knitted fabric of the basic structure preferably has an approximate 
rectangular structure or approximate quadratic structure knitted from 
yarns. Honeycomb structures or structures with approximately circular 
openings or other polygonal structures are however also conceivable. 
Preferred versions of such knitted fabrics are explained in more detail in 
the description of the embodiments with the help of Figures. The desired 
stress/strain behavior can be achieved with knitted structures of this 
type, i.e. the basic structure stretches more than the tissue region 
destined to receive the implant below the critical force and less than 
this tissue region above the critical force, the critical force being 
below the highest load allowable for this tissue region. 
There are various possibilities for connecting the stiffening material to 
the basic structure. Thus, the stiffening material can e.g. have 
resorbable yarns or thin monofilaments woven into the basic structure, it 
can have a film which is applied to one side or both sides of the basic 
structure, or it can have a coating applied to the material of the knitted 
fabric. Combinations of these are also conceivable. 
Suitable materials for the basic structure include but are not limited to 
polyamides (e.g. nylon-6, nylon 6,6, nylon 610, etc.) polyolefins (e.g. 
polyethylene, polypropylene [including isotatic and syndiotactic polymers] 
and copolymers of polyethylene and polypropylene), polyesters (e.g. 
polybutylene terephthalate, polyethylene terephthalate, etc.) hydrolyzable 
aliphatic polyesters (e.g. polymers containing glycolic acid repeating 
units, lactic acid repeating units, (including l, d, dl and meso lactide 
and combinations thereof), 3-methyl-1,4-dioxan 2,5-dione, 
3,3-diethyl-1,4-dioxan-2,5-one, 1,4-dioxan-2-one, 1,4-dioxepan-2-one, 
1,5-dioxepan-2-one, delta-valerolactone, epsilon-decalactone, 
pivalolactone, gamma-butyrolactone, ethylene carbonate, 1,3-dioxan-2-one, 
4,4-dimethyl-1, 3-dioxan-2-one, epsilon-caprolactone, combinations and 
blends thereof.) 
Preferred materials are yarns of polypropylene, polyethylene and 
polyglactin 910 (a copolymer composed of about 90 percent by weight 
glycolide and about 10 percent by weight lactide) polylactide, 
polyglycolide, mixture and combinations of such yarns. 
Suitable stiffening materials are hydrolyzable materials including but not 
limited to yarns or films of hydrolyzable aliphatic polyesters (e.g. 
polymers containing glycolic acid, lactic acid, glycolide, lactide (l, d, 
dl and meso lactide and combinations thereof), 
3-methyl-1,4-dioxan-2,5-dione, 3,3-diethyl-1,4-dioxan-2,5-one, 1,4 
dioxan-2-one, 1,4-dioxepan-2-one, 1,5-dioxepan-2-one, delta-valerolactone, 
epsilon-decalactone, pivalolactone, gamma-butyrolactone, ethylene 
carbonate, 1,3-dioxan-2-one, 4,4-dimethyl-1, 3-dioxan-2-one, 
epsilon-caprolactone, combinations and blends thereof). 
Advantageous materials for the basic structure are e.g. polypropylene, 
polyester, polyglactin 910, polylactide yarns, polyglycolide yarns, 
poly-p-dioxanone yarns, but also copolymers, mixtures or combinations of 
such materials. 
Suitable as the stiffening material are e.g. yarns or films of 
poly-p-dioxanone, yarns or films of polyglactin (i.e. glycolide/lactide 
copolymers), yarns or films of polylactide, yarns or films of other 
copolymers of these materials, monofilaments of such materials (e.g. with 
thread thicknesses of 0.01 mm to 0.2 mm in diameter), coating waxes made 
from such materials, in particular from polyglactin 630 and others. 
Mixtures of synthetic resorbable materials whose resorption time lies in 
the desired range can also be used for the stiffening material. If the 
stiffening material is of a textile nature, the result of the in vivo 
decrease in strength is that, after an implantation time of typically 2 to 
50 days, the residual tearing strength is still about 10% of the initial 
tearing strength. 
The material of the basic structure is preferably not dyed, in order that 
the basic structure, which does after all remain in the body for a long 
time or permanently after implantation, shows no undesired foreign body 
reaction as a result of the dye. On the other hand, it can be advantageous 
if the stiffening material is dyed. This does in fact permit a better 
visual check on the implant during the operation. During resorption the 
dye disappears, so that no dye remains in the body in the longer term and 
thus no undesired side-effects occur. 
FIGS. 1 to 5 show magnified schematic views of different versions of the 
knitted fabric of the flexible basic structure of the areal implant 
according to the invention. The figures are drawn on the basis of scanning 
electron microscope photographs taken at roughly 25 times magnification. 
Variant A of the knitted fabric according to FIG. 1 has an approximate 
quadratic structure, the crosspiece length-being about 3 mm in each case. 
Variant B of the knitted fabric according to FIG. 2 also has an 
approximate quadratic structure. However, the crosspiece length is larger 
here and is about 5 mm. Variant C of the knitted fabric, shown in FIG. 3, 
has differently sized openings or pores, the area of the large pores being 
greater than 0.5 mm.sup.2 and that of the smaller pores being less than 
0.5 mm.sup.2. Variants D and E of the knitted fabric, shown in FIGS. 4 and 
5, have other structures. 
It is clearly recognizable from FIGS. 1 to 5 that the majority of the pores 
are larger than 0.5 mm.sup.2. Thus, after implantation, the flexible basic 
structure of the areal implant can be grown through by tissue in 
satisfactory manner, which leads to a secure anchorage in the body of the 
patient and to a reliable absorption of forces by the implant. 
TABLE 1 
__________________________________________________________________________ 
Data for five flexible basic structures according to the invention 
(variants A to E) 
and for a conventional implant net (H) made of polypropylene (polypr.) 
Variants 
A B C D E H 
__________________________________________________________________________ 
Material Polypr. 
Polypr. 
Polypr. 
Polypr. 
Polypr. 
Polypr. 
Filament multifilament 
multifilament 
multifilament 
multifilament 
multifilament 
monofilament 
Thread systems 3 3 3 3 3 1 
Number of courses per cm (longitudinal) 
220 220 160 186 212 62 
Number of wales per cm (transverse) 
52 38 57 64 72 46 
Yarn fineness in tex [g/1000 m] 
6.7 6.7 6.7 6.7 6.7 20.6 
Pore size (approx.) of the pores &gt; 0.5 mm.sup.2 
3 .times. 3 
4 .times. 4 
1.3 .times. 1.3 
2 .times. 3.3 
1.3 .times. 3.3 
[mm.sup.2] 
Proportion of pores [%] 
93 95 83.5 
Thickness [mm] 0.41 0.4 0.7 
Areal weight [g/m.sup.2 ] 
26.8 20.1 31.4 36.2 40 109 
Seam tear-out force per cm (longitudinal) 
17.5 13.5 20.1 20.7 23 57 
[N/cm] 
Seam tear-out force per cm (transverse) 
22.7 22.4 26.3 31.7 36.1 75 
[N/cm] 
Plunger pressing test (similar to DIN 54307) 
F.sub.max [N] 464 415 460 488 625 2370 
Plunger path length at F.sub.max [mm] 
44.5 44.1 40.4 40.6 44.8 44.7 
Stress at r.sub.contact [N/cm] 
17.7 16.1 18.8 19.9 23.8 90.9 
Deformation [%] 34.5 33.9 28.6 28.9 34.9 34.1 
Elongation at break [%] 
39.5 39.1 35.8 36.0 39.7 39.7 
Strip tensile test 
Tearing strength (longitudinal) [N/cm] 
33 25 33 37 45 150 
Elongation at break (longitudinal) [%] 
37.9 28.2 25.2 49.5 40.3 80.4 
__________________________________________________________________________ 
Given in Table 1 are data for the individual variants A to E of the 
flexible basic structure of the areal implant according to the invention 
and, for comparison, the corresponding data for a conventional implant 
net. All the fabric was knitted on a Crochet Galoon knitting machine. 
Variants A to E are all knitted from multifilament polypropylene, using 
three thread systems. The conventional implant net consists of 
monofilament polypropylene, using one thread system. Table 1 shows the 
number of courses per centimeter, the number of wales per centimeter, the 
yarn fineness, the dimensions of the pores larger than 0.5 mm.sup.2, the 
proportion of pores (relative to the total area of the knitted fabric or 
of the conventional implant net) and the thickness. Compared with the 
conventional implant net, variants A and B have a larger proportion of 
pores and a smaller thickness. As Table 1 also shows, variants A to E have 
a relatively low areal weight, which in all cases is below 50 g/m.sup.2 
and is thus clearly smaller than that of the conventional implant net. 
For variants A to E, the seam tear-out force per centimeter of seam length, 
measured along and across the knitted fabric or the conventional implant 
net, is as a rule more than 16 N/cm, the value quoted by Klinge for the 
maximum wall stress at the edge of an abdominal tissue region. 
The stress-strain behavior of the knitted fabrics or of the conventional 
implant net can be best described quantitatively using a plunger pressing 
test related to DIN 54307. In the textile industry, material properties 
related to area are measured with such plunger pressing tests. 
FIG. 6 shows a schematic view of a device for carrying out plunger pressing 
tests. A semispherical plunger 1, which is attached to a shank 2, is moved 
in the direction of the arrow, i.e. along the axis of symmetry. A sample 5 
of the knitted fabric to be investigated or of a conventional implant net 
is clamped between an upper ring 3 and a lower ring 4. When the plunger 1 
is advanced in a downwards direction, it pushes the sample 5 in a 
downwards direction. The greater the deformation of the sample 5, the 
greater the force F exerted on the plunger 1 by the sample 5 becomes. The 
force F and the plunger path length s, which is a measure of the 
deformation of the sample 5, are measured, wherein s=0 when the lowest 
point of the plunger 1 is located in the plane of the sample 5. With the 
device used for the plunger pressing tests the plunger radius is 50 mm. 
The internal radius of the upper ring 3 and of the lower ring 4 is 56.4 
mm, so that the effective surface area of the sample 5 is 100 cm.sup.2. 
Given in Table 1 for variants A to E and for the conventional implant net 
are the maximum force F.sub.max applied during the plunger pressing test, 
at which the first damage to the sample occurs (in the middle region of 
the sample), and the associated plunger path length s.sub.max. From this, 
the so-called stress at r.sub.contact, which corresponds to the so-called 
wall stress in N/cm, can be calculated. In the sample, the stress at 
r.sub.contact occurs along the circular line where, in the case of plunger 
path length s.sub.max, the sample region abutting the plunger passes into 
the sample edge region which does not touch the plunger directly and 
extends as far as the rings 3, 4. At this stress, the deformation given in 
Table 1 arises which results from the change in length of the sample at 
r.sub.contact measured in the peripheral direction, relative to the 
corresponding peripheral length of the non-deformed sample. From the test 
data, it is also possible to calculate the elongation at break, also given 
in Table 1, which is higher than the deformation since the sample in the 
plunger pressing test tears, not at r.sub.contact, but in the middle 
region where it is more stretched than at r.sub.contact. 
It is clear from Table 1 that for all variants A to E the stress at 
r.sub.contact is greater than or equal to 16 N/cm, i.e. at least as large 
as the maximum wall stress at the edge of an abdominal tissue region (16 
N/cm) quoted by Klinge. The much greater value in the case of the 
conventional implant net is physiologically unnecessary. 
Table 1 also shows the results of a strip tensile test carried out on 
samples of variants A to E and the conventional implant net. For this, the 
tearing force per centimeter of sample width (tearing strength) along the 
sample direction and the elongation at break are determined. It is, 
however, to be taken into consideration here that the values can be 
severely distorted by the test (contraction upon drawing), making the 
plunger pressing test more informative. 
For variants A to E of the knitted fabric, the tearing strengths lie in the 
range from 25 to 45 N/cm and are therefore at least as large as the 
tearing strength of the fasciae quoted by Klinge (20 to 30 N/cm). The much 
higher tearing strength of the conventional implant net is again not 
necessary. 
FIG. 7 shows a complete plunger force--plunger path length diagram, 
determined using a plunger pressing test, for the knitted fabric of 
variant B compared with the conventional implant net made of polypropylene 
(H). The curve for variant B ends at the values for F.sub.max and 
S.sub.max given in Table 1, whilst the curve for the conventional implant 
net is not shown in full, but stops at F=500 N. It is clear to see that, 
for the implant of the invention according to variant B, the plunger force 
F is small even with relatively large plunger path lengths s. Only at 
larger values of s does the curve rise sharply. With the conventional 
implant net, the plunger force F is already large at average plunger path 
lengths s. 
The plunger force--plunger path length diagrams as in FIG. 7 can be 
converted into force-length change diagrams or into stress-strain 
diagrams. In the case of the latter, stress is to be understood as the 
force per centimeter of sample width. 
Moreover, the change in length of the sample is related to the total length 
of the sample (before strain) and is thus independent of the total length 
of the sample itself. FIG. 8 shows such a stress--strain diagram of the 
flexible basic structure according to variant A, as results from the 
plunger pressing test. 
A stress--strain diagram determined using rat musculature is also shown, 
which was not, however, obtained by a plunger pressing test, which was not 
possible to carry out with rat musculature because of the sample size 
required, but on the basis of a strip tensile test on a sample strip 
approximately 1 cm in width. Measurements on the rat musculature were 
taken at a musculature thickness which corresponds approximately to that 
of a human abdominal wall, wherein the spread, as in the case of any 
biological sample, can be correspondingly large. 
A narrow sample strip contracts in the tensile test, which leads to a much 
greater elongation at a given tensile force per strip width (stress) than 
if elongation takes place simultaneously in several spatial directions, as 
during the plunger pressing test. The curve for the rat musculature 
cannot, therefore, be compared directly with the stress--strain diagram 
obtained in the plunger pressing test for the flexible basic structure 
according to variant A. For this reason, another stress-strain diagram is 
shown for the flexible basic structure according to variant A which, as 
with the rat musculature, was determined using a strip tensile test, using 
a sample strip 1 cm in width. Even at an elongation of 100%, the sample 
had still not torn, which is not inconsistent with the elongation at break 
given in Table 1 for the strip tensile test, because the values in Table 1 
apply to strips with a larger width. 
In order to achieve an elongation up to about 78%, the forces required for 
variant A are smaller than for rat musculature, and for elongations of 
less than 50%, even much smaller. This means that a knitted fabric 
according to variant A implanted into muscle stretches with it during 
usual movements, without appreciable forces being necessary for this. 
Therefore, the implant does not have an inconvenient effect. However, if 
in the case of extreme loads, the forces which arise approach the highest 
load which is allowable for the tissue region into which the implant is 
inserted (which corresponds in FIG. 8 to about 18 N/cm), the knitted 
fabric of the basic structure undergoes less pronounced further stretching 
than the tissue, so that the knitted fabric of the basic structure is able 
to absorb the forces. The transition between the two elongation or 
stretching regions takes place at a critical force which results from the 
point of intersection of the curves in FIG. 8. The critical force defined 
in this way should be below the highest load which is allowable for the 
tissue region. 
The fact that in FIG. 8 the critical force and the highest load which is 
allowable for the tissue region (to be more precise, the corresponding 
stresses) are approximately the same size is due to the tests with rat 
musculature which are difficult to carry out. FIG. 8 is intended only to 
illustrate the two described elongation regions. Quantitative measurements 
on the flexible basic structures are better carried out using plunger 
pressing tests, and Klinge's data can for example be referred to for 
tissue, see above. 
Table 2 shows the plunger forces F measured in the plunger pressing test as 
a function of the plunger path length s for variants A to E, i.e. values 
as are shown graphically in FIG. 7 for variant B. By way of comparison, 
the values for the conventional implant net made of polypropylene (H) 
according to Table 1 and for another conventional implant net made of 
polyester (M) are also listed. The data for F.sub.max and for the plunger 
path length at F.sub.max are taken from Table 1. In the plunger pressing 
test initial damage to the investigated sample takes place at F.sub.max. 
Table 2 Plunger force F measured in the plunger pressing test related to 
DIN 54307 as a function of the plunger path length s, and F.sub.max (in N) 
and s (F.sub.max) (in mm) for five flexible basic structures according to 
the invention (variants A to E) and for two conventional implant nets made 
of polypropylene (H) and of polyester (M). 
______________________________________ 
s A B C D E M H 
[mm] F[N] F[N] F[N] F[N] F[N] F[N] F[N] 
______________________________________ 
10 &lt;10 &lt;10 &lt;10 &lt;10 &lt;10 ca.10 ca.50 
15 ca.- ca.20 ca.10 ca.20 ca.10 ca.35 ca.135 
15 
20 ca.- ca.35 ca.30 ca.40 ca.40 ca.85 ca.300 
30 
25 ca.- ca.70 ca.75 ca.80 ca.80 ca.160 
ca.600 
70 
30 ca.- ca.130 ca.150 
ca.170 
ca.150 
ca.280 
130 
F.sub.max 
464 420 460 490 630 460 2370 
s 45 44 40 41 45 37 45 
(F.sub.MAX) 
______________________________________ 
As already seen, F.sub.max is much larger for the conventional implant net 
made of polypropylene than for variants A to E. F.sub.max for the 
conventional implant net made of polyester is of the same order of 
magnitude as for variants A to E. However, for the plunger path lengths up 
to 30 mm listed in Table 2, the plunger force for variants A to E is much 
smaller than for the conventional implant net made of polyester, which 
again illustrates the superiority of the implant according to the 
invention. 
Both the knitted fabric of the basic structure of the areal implant 
according to the invention and conventional implant nets show a hysteresis 
behavior which can be determined in the plunger pressing test. The plunger 
force--plunger path length diagram in FIG. 9 shows schematically how in 
the case of a new sample the plunger force F, starting from the plunger 
path length s=0, increases to a value Fo which is defined here as the 
value of the plunger force at a plunger path length of 20 mm. If the 
plunger is withdrawn, the plunger force already returns to zero at a 
plunger path length s.sub.1. 
Table 3 compares the force F.sub.0 and the plunger path length s.sub.1, 
during one plunger pressing test (n=1) and after 5,000 plunger pressing 
tests (n=5,000) for a conventional implant net made of polyglactin 910, a 
conventional implant net made of polypropylene and the knitted fabric of 
the basic structure according to variant B. In order to ensure a secure 
abutment of the sample against the plunger, the force was not returned to 
zero in the plunger pressing tests (as in FIG. 9), but operated at a 
residual force of 0.5 N. It is clear from Table 3 that variant B of the 
flexible basic structure of the implant according to the invention offers 
a clearly lower resistance to the alternating load, which is to simulate 
the movement of an abdominal wall, than do the conventional implant nets. 
Table 3 Hysteresis behavior of different implants after n alternating 
loads, measured in the plunger pressing test at a plunger path length 
between 0 and 20 mm and a plunger residual force of 0.5 N; see text 
______________________________________ 
n = 1 n = 5000 
Implant F.sub.o [N] 
S.sub.1 [MM] 
F.sub.o [N] 
S.sub.1 [MM] 
______________________________________ 
Conventional 
ca.150 ca.8 ca.114 ca.15.5 
implant net made 
of polyglactin 
910, coarse-meshed 
Conventional 
ca.240 ca.4 ca.164 ca.12.5 
implant net made 
of polypropylene 
Basic ca.45 ca.7.5 ca.30 ca.14.2 
structure according 
to the invention, 
variant B 
______________________________________ 
FIG. 10 shows a magnified schematic view of the flexible basic structure 
according to variant A, into which a multifilament thread made of 
polyglactin 910 is woven for stiffening. Shown in FIG. 11 is a magnified 
schematic view of the flexible basic structure according to variant B 
which is provided with a coating of polyglactin 630. Polyglactin 630 is a 
copolymer of glycolide and lactide in the ratio 6:3 and, just like 
polyglactin 910, is resorbable. 
The flexible basic structure is stiffened by the woven-in thread or by the 
coating, as a result of which handling of the implant according to the 
invention during use, in particular during the operation, is much 
improved. Since the stiffening material is resorbable, the rigidity of the 
implant in the body of the patient decreases with time, until the implant 
has achieved the properties of the basic structure with its favorable 
stress/strain behavior, as explained earlier. Table 4 compares the bending 
resistances of the knitted fabric according to variant A (FIG. 1), of the 
knitted fabric according to variant B (FIG. 2), of the knitted fabric 
according to variant A with stiffening thread (FIG. 10), of the knitted 
fabric according to variant B with stiffening coating (FIG. 11) and of a 
conventional implant net made of polypropylene. The bending resistances 
quoted were determined in a three-point bending test with the supports 15 
mm apart and a sample width of 15 mm. The conventional implant, rated as 
good by users as regards handling, has a bending resistance of ca. 0.15 to 
0.20 N/mm. The bending resistances of the stiffened knitted fabrics are 
clearly higher than those of the original basic structures and are between 
ca. 0.05 and 0.42 N/mm. The latter value is even much higher than that for 
the previously known implant net. 
TABLE 4 
______________________________________ 
Bending resistance of different implants, 
determined by comparative measurement in the three-point 
bending test with the supports 15 mm apart and a sample 
width of 15 mm 
Implant Bending resistance [N/mm] 
______________________________________ 
Basic structure according to 
ca.0.03 
the invention, variant A 
Basic structure according to 
ca.0.015 
the invention, variant B 
Basic structure according to the 
ca.0.05 
invention, variant A, stiffened 
by yarn (4 .times. 80 den) made of 
polyglactin 910 
Basic structure according to 
ca.0.42 
the invention, variant B, 
stiffened by coating made of 
polyglactin 630 
Conventional implant net made of 
ca.0.15 to 0.2 
polypropylene 
______________________________________ 
The initial rigidity of the areal implant according to the invention can be 
varied within wide limits by means of the type, the quantity and the 
structure of the applied or incorporated stiffening resorbable material.