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DOI: 10.1258/002367787781268828

1987 21: 195Lab AnimM. Walter, U. Brenner, W. Holzmller and J. M. MllerExperiments with a biological material for the closure of incisional hernias

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Laboratory Animals (1987) 21,195-200

Experiments with a biological material for the closure of

incisional hernias

M. WALTER, U. BRENNER, W. HOLZMULLER&J. M. MULLER

195

Chirurgischen Klinik und Poliklinik der Universitat Kaln, Linden/hal, Joseph-Stelzmann-Straf3e 9,5000 Kaln

41, Federal Republic of Germany

Summary

A new preparation process was studied which

should allow the implantation of collagen type I

in its native structure in reconstructive surgery,in this special case for closure of incisional

hernias. As experimental animals we used 30

female Lewis rats. A defect of the anterior

abdominal wall measuring 3 cm x 4 cm was

closed with our collagen substitute. Biopsies

taken after 4, 6 and 8 weeks were examined

morphologically. As criteria for revitalization

and revascularization we used the type of

infiltrating cells, the depth and density of

infiltration and the formation of new blood

vessels. After 4 weeks the implants were infil-trated by fibroblasts that decreased in density

towards the centre. Good revascularization

could be seen on the muscle-implant interface.

After 6 weeks the density of infiltrating cells

had increased markedly even to the centre of

the collagen implant. Sporadically small vessels

could be seen. Eight weeks after implantation

the density of infiltrated cells was at the same

high level, and capillary bundles could be seen

within the whole implant. We believe that this

collagen implant is suitable for the closure ofhernias as shown by its physical and

morphological properties. In particular it

appears to guarantee an earlier and tighter

closure of hernias than other materials.

Keywords: Biocompatible materials; Collagen;

Hernia; Surgery, reconstructive

The definitive operative repair of large in-

cisional hernias may be quite difficult, d~pend-Received 3 July 1985; in revised form 4 February 1986.Accepted 14 October 1986.

ing on previous operations and localization of

the hernia (Axhausen, 1956; Kothe, 1958;

Cassau & Siewert, 1967; Drevs, 1970; Gerhard

&Sior, 1978; Schleicher, 1980). When closureof the hernia using autogenous tissues (Rueff

& SchmidtIer, 1979) is not possible and inorga-

nic materials are implanted instead, the results

are not always satisfactory. The main problems

with implantation of an inorganic material are

rejection, healing and ageing of the implants

(Joppich, 1970).

For this reason investigations on organic

materials for the reconstruction of incisional

hernias have gained increasing attention during

the last few years (Jager, 1971; Sarmah &Holl-Altan, 1984). Encouraging results with

lyophilized human dura mater have been

obtained in neurosurgery and orthopaedic

surgery and this material has therefore been

studied intensively (Joppich, 1970; Jager, 1971;

Steinke, 1974; Schleicher, 1980; Sarmah &

Holl-Altan, 1984). Latteri reported good re-

sults in his studies using 'Iyodura' for the

closure of diaphragmatic hernias but the

material was found to be not fully satisfactory

because the collagen is denatured by the usualmethods of preparation and hence is reab-

sorbed and replaced by the host (Joppich,

1970). Revascularization and impregnation

with cells is judged in different ways by

different workers but they agree that reabsorp-

tion and replacement of the implanted collagen

fibres takes place. Bovine xenografts are used

in vascular surgery with quite encouraging

results that demonstrate revascularization

and 're-utilization' of the implanted collagen

(Walter & Schmitz, 1975; Pahre, 1980).

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196

Materials and methods

Collagen type I

of bovine ongIn was thematerial of our choice because the amino acid

sequence of bovine collagen type Iis closely

related to that of man (Gay, Walter & Kiihn,

1976). Furthermore bovine grafts are already

used with great success for other types of

surgery (Walter & Schmitz, 1975; Walter &

Walter, 1983-4).

The raw material for our collagen implant is

the pericardium of cattle. Until the preparation

process is started within the first 48 h after

slaughtering the animals, the material is kept inice-water. The first step is the treatment with

the proteolytic enzyme ficin at a temperature

of 37C and a pH of 60. 10 g ficin and] g

L-cysteine are added to I I of water. Depending

on the thickness of the material this process

takes 30-120 min to remove all elastic and

collagen type III fibres and all cellular ele-

ments. Stabilization is carried out by cross-

linking the fibres by the use of glutardialdehy-

de for 7 days. After treatment with sodium

borate for 24 h the material undergoes reduc-tion and is thereby rendered insoluble.

Walter, Brenner, Holzmuller &Muller

Sterilization is carried out chemically (using a

50% alcohol plus 1% propylene oxide mixture)or by y radiation (Walter & Schmitz, 1975;

Pahre, 1980; Walter & Walter, 1983-4). The

material is stored at room temperature in

phosphate-buffered saline solution. Morpho-

logical studies of the material show collagen

type Ifibres in their native structure with a

diameter of 30-40 nm.

We used 30 female Lewis rats which were

housed five to a cage and were given food and

water ad libitum. A defect of the anterior

abdominal wall measuring 3 cm x 4 em wasclosed by the use of our implant which had

exactly the same size (Fig. 1). Biopsies taken

after 4, 6 and 8 weeks were studied

morphologically. The following criteria were

used to assess the revitalization: (1) the type of

cells that infiltrated the implant; (2) the depth

of cell infiltration; (3) revascularization.

Results

Macroscopically the closure of the defect of the

anterior abdominal wall was complete in allcases, and the collagen implant healed without

Fig. I. Site of the operation.



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Biological material for closure of incisional hernias

reaction of the surrounding tissue. No seroma

or rejection could be seen.

After 4 weeks the peripheral areas of the

implants were impregnated with fibroblasts

and fibrocytes that decreased in density to-

wards the centre. No other type of cells, in

particular no basophilic round cells, were

evident (Figs 2 and 3). In these areas a !;irge

number of new small blood vessels could be

seen. After 6 weeks even the centres of the

implants were permeated by fibroblasts, with

increasing vascularization (Fig. 4). Eight weeks

post-operatively cell migration and re-

vascularization had increased markedly and

reached its maximum. The vascular network

was now tightly woven and newly formed

blood vessels were evident throughout the

implant (Fig. 5).

Fig. 2. Implant-muscle interface after 4 weeks. Fibroblastsand fibrocytes can be seen. (Haematoxylin and eosin;

56x.)

197

Discussion

Although they have unquestionable advan-

tages over biological materials the allogeneic

materials used nowadays for the closure of

incisional hernias have the disadvantage of

ageing. Furthermore they are not of consistent

stability. Teflon for example undergoes shrink-

ing, and Dacron lengthens during ageing (Jop-

pich, 1970). The most frequently used

biomaterial today is lyophilized human dura.

Revitalization of this material is disputed by

several investigators. Some workers (Joppich,

1970; Jager, 1971; Haddad & Macon, 1980;

Gr6zinger, 1981) deny impregnation with

connective-tissue cells or newly formed vessels

and discuss reabsorption and replacement by

the host, while others (Pahre, 1980) consider

that the denatured collagen is used at least as

a live matrix during the healing process.

Reabsorption and replacement by scar tissue

appears not to have been discussed (Pahre,

1980). Furthermore after 8-9 weeks the col-

lagen fibres of the denatured collagenous

implant are located in longitudinal sections

caused by traction (Jager, 1971). This observa-

tion is not surprising because stabilization of

the material is carried out only by y radiation.

In addition the mechanical properties are

degraded by lyophilization (Jager, 1971). Start-

ing from the principle that collagen type I in its

native structure is not reabsorbed or altered by

the host (Pahre, 1980), we investigated a new

preparation of collagen I implants in their

biological texture without denaturation of the

fibres during preparation.

We consider that biomaterials prepared in

this way are to be preferred because there is no

need of reabsorption and they are incorporated

and 're-used' by the host. The mechanical

properties of the collagen fibres in our implant

reach the equivalent of steel wires of the same

diameter (Walter & Schmitz, 1975; Pahre,

1980; Decurtins &Buchmann, 1982; Walter &

Walter, 1983-4; Weadock, Altan & Silver,

1983-4). Morphological examination of the

implants after sacrificing the animals at 4, 6

and 8 weeks demonstrated good incorporation



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198 Walter, Brenner, Holzmuller & Muller

Fig. 3. Newly formed collagen fibres between the implant scaffolding. (Haematoxylin and eosin; 150x.)

Fig. 4. Tightly woven vascular network 6 weeks post-operatively. (Haematoxylin and eosin; 15x.)



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Biological material for closure of incisional hernias 199

Fig. 5. Revitalization of the collagen implant, demonstrated by blood vessels and fibroblasts. (Haematoxylin and eosin;75x .)

and 'revitalization' without exception. At 4

weeks post-operatively the muscle-implant in-

terface and at 6 weeks post-operatively even

the central areas of the implants showed a

dense impregnation with fibroblasts and fibro-

cytes, with increasing revascularization during

the period of observation. After 8 weeks the

density of cells was at the same high levelthroughout the implant. Small vessels and

capillary bundles were evident. No host-

versus-graft reaction could be demonstrated

References

Axhausen, W. (1956). Zur postoperativen Wundrupter.

Zentralblatt fur Chirurgie 81, 1297.Cassau, D. & Siewert, R. (1967). Die vollstandige

Wundrupter in neuer Siehl. Chirurgie 38, 381.Decurtins, M. & Buchmann, P. (1982). Bovines Perikard

- Ein neues Material zm plastischen Deckung groBerBauchwanddehiszenzen. Research in ExperimentalMedicine 180, 11-14.

either clinically or morphologically. In particu-

lar no seroma, a quite usual complication with

allogeneic materials, could be seen.

Clearly, an observation period of 8 weeks is

much too short to prove that the material used

does not undergo weakening but other studies

with bovine collagen type I, prepared in the

same way, suggest incorporation withoutweakening (Walter & Schmitz, 1975; Pahre,

1980; Weadock, Altan & Silver, 1983-4).

Further studies on this aspect need to be made.

Drevs, S. (1970). Untersuchungen uber intermolekulare

Quervernetzungen des Collagens. Inaugural-Dissertation, Naturwissenschaftl. Fakultat der Universi-tat Munchen.

Gay, S., Walter, P. & Kuhn, K. (1976). Charakterisierung

und Vertei1ung der Kollagentypen in BlutgefaBersatz-materialien aus der A. carotis communis vom Kalb.

Klinische Wochenschrift 54, 889.



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Gerhard, A. & Sior, H. (]978). Ubcr die Haufigkeit der

Ruptur von Laparotomiewunden. Zentralblall fur Chir-urgie 83, 730-736.

Grozinger, K. H. (198]). Spatergcbnisse nach Behandlunggrol3er Bauchwandbriiche mit Iyophilisierter Dura. Chir-urgische Praxis 28, 33.

Haddad, V. & Macon, W. L. (1980). Abdominal wound

dehiscence and evisceration: contributing factors andimproved mortality. American Surgeon 9, 508-513.

Jager, M. (1971). Experimentelle Untersuchungen zurVerwendung der Iyophilisierten Dura im Bereich derWiederherstellung chirurgie. Chirurg 42, 266.

Joppich, L (1970). Gewebeersatz durch lyophilisierte Dura

in der Abdominalchirurgie. Langenbecks Archiv furChirurgie 327, 1124.

Kothe, E. (]958). Die Atiologie der Nahtdehiscenz nachLaparotomie. Langenbecks Archiv fur Klinische Chirur-gie 289, 687.

Pahre, K. (1980). Zur Frage der 'Revitalisierung' denatur-ierten Kollagens. Inaugural-Dissertation, TierarztlicheFakultat der Universitat Miinchen.

Waiter, Brenner, Holzmuller &Muller

Rueff, F. L. & Schmidtler, F. (1979). Zur Korrektur von

Bauchnarbenbriichen und deren Rezidiven. Zentralblallfur Chirurgie ]04, 464-473.

Sarmah, B. D. & Holl-Altan, R. T. J. (1984). Porcinedermal collagen repair of incisional hernia. British

Journal of Surgery 7], 524-525.Schleicher, P. (]980). Die komplette Wunddehiszenz aus

klinischer und experimenteller Siehl. Inaugural-

Dissertation, Medizin Fakultat der Technischen Univer-sitat Miinchen.

Steinke, H. J. (]974). Duratransplantate, Anwendung undEinheilung. Zentralblall fur Chirurgie 99, 1601.

Walter, M. & Walter, P. (]983-]984). Dermodress iur

Versorgung grol3llachiger Hautdefekte. ChirurgischePraxis 32, ]27.

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