small intestine submucosa (sis) implants in experimental ipom repair

8
Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair Alexander H. Petter-Puchner, M.D,* ,2 Rene H. Fortelny, M.D,,1,2 Nadja Walder, M.D,* Salvador Morales- Conde, M.D,Simone Gruber-Blum, M.D,* Wolfgang O ¨ hlinger, M.D,* and Heinz Redl, Ph.D* *Ludwig Boltzmann Institute for Experimental and Clinical Traumatology and Cluster for Tissue Regeneration, Vienna, Austria; II Department of Surgery, Wilhelminenspital der Stadt Wien, Vienna, Austria; and Advanced Laparoscopic Unit, University Hospital Virgen del RocA ˜ o, Sevilla, Spain Submitted for publication October 30, 2008 Background. Synthetic meshes can cause adverse effects (e.g., adhesions, mesh infection) in intraperito- neal onlay mesh repair (IPOM). Although data for its biocompatibility as well as degradation behavior is still scarce, small intestine submucosa (SIS) implants have been suggested as a favorable alternative for IPOM repair. The aim of the study was to assess safety and efficacy of SIS used as allo- or xenograft in an ex- perimental model of IPOM repair, with the purpose of creating a critical awareness for specific aspects of the biomesh concept among researchers and surgeons alike. Main outcome parameters were adhesion forma- tion, tissue integration, shrinkage, and dislocation. Materials and Methods. Open IPOM repair was per- formed in 16 Sprague Dawley rats and two minipigs. SIS implants were 2 3 2cm in rats (one per animal) and 6 3 8cm in pigs (four per animal). All implants were fixed with six nonresorbable sutures. Observa- tion period was 17 and 28 d (n [ 8) in rats and 28 d in pigs. Outcome parameters were assessed macroscopi- cally, and histologic samples (H and E staining) were obtained. Results. Upon autopsy, SIS appeared to be only mod- erately integrated. Dislocation of five SIS implants in the rats and of two SIS implants in the pigs were observed although all sutures were still in place. No seroma forma- tion or infection was detected macroscopically, but sub- stantial shrinkage and adhesion formation at the margins of implants and suture sites were frequently ob- served. Histology confirmed the macroscopic finding of limited integration and substantial shrinkage. The path- omorphology was similar in both species. Conclusions. Small intestine submucosa implants are susceptible to shrinkage, dislocation, and adhesion formation in experimental IPOM repair in rats and pigs. These findings are in accordance with literature and warrant further investigations of SIS implants in hernia repair. Ó 2010 Elsevier Inc. All rights reserved. Key Words: porcine small intestine submucosa; experimental IPOM; shrinkage; adhesions. INTRODUCTION Intraperitoneal onlay mesh repair (IPOM) has be- come a standard procedure for the repair of incisional hernias [1, 2]. Although this technique has obvious technical advantages, including tension-free repair and laparoscopic detection of occult, multiple hernias, it can be associated with some adverse effects such as adhesion formation, mesh infection or shrinkage. The synthetic IPOM meshes most commonly used are made of polymers, often layered with absorbable anti- adhesive barriers [3–5]. Along with refined mesh tech- nologies, the atraumatic fixation of meshes, for example with fibrin sealant (FS) contribute to reducing compli- cations in IPOM [6]. Recent literature suggests the potential benefits of bi- omeshes. Biomeshes can be divided into two main cate- gories. First, products derived from animal sources, e.g., porcine small intestine submucosa (SIS; Surgisis, Cook, Bloomington, IN), porcine cross linked collagen (PCL; PermaCol, Covidien, Aldershot, UK) and bovine pericard (TuM; Tutomesh, Tutogen, Neunkirchen, Ger- many) [7–11]. Implants processed from decellularized human cadaveric skin (AD; Alloderm, KCI, Branch- burg, NJ) form a second category of human allografts 1 To whom correspondence and reprint requests should be addressed at Department of Visceral Surgery, Wilhelminenspital, Vienna, Austria, Montleartstrasse 37, A-1171-Vienna. E-mail: rene. [email protected]. 2 These two authors contributed equally to this study. 0022-4804/$36.00 Ó 2010 Elsevier Inc. All rights reserved. 264 Journal of Surgical Research 161, 264–271 (2010) doi:10.1016/j.jss.2009.04.007

Upload: alexander-h-petter-puchner

Post on 27-Oct-2016

215 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

Journal of Surgical Research 161, 264–271 (2010)doi:10.1016/j.jss.2009.04.007

Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

Alexander H. Petter-Puchner, M.D,*,2 Rene H. Fortelny, M.D,†,1,2 Nadja Walder, M.D,* Salvador Morales-Conde, M.D,‡ Simone Gruber-Blum, M.D,* Wolfgang Ohlinger, M.D,* and Heinz Redl, Ph.D*

*Ludwig Boltzmann Institute for Experimental and Clinical Traumatology and Cluster for Tissue Regeneration, Vienna, Austria;†II Department of Surgery, Wilhelminenspital der Stadt Wien, Vienna, Austria; and ‡Advanced Laparoscopic Unit,

University Hospital Virgen del RocAo, Sevilla, Spain

Submitted for publication October 30, 2008

Background. Synthetic meshes can cause adverseeffects (e.g., adhesions, mesh infection) in intraperito-neal onlay mesh repair (IPOM). Although data for itsbiocompatibility as well as degradation behavior isstill scarce, small intestine submucosa (SIS) implantshave been suggested as a favorable alternative forIPOM repair. The aim of the study was to assess safetyand efficacy of SIS used as allo- or xenograft in an ex-perimental model of IPOM repair, with the purposeof creating a critical awareness for specific aspects ofthe biomesh concept among researchers and surgeonsalike. Main outcome parameters were adhesion forma-tion, tissue integration, shrinkage, and dislocation.

Materials and Methods. Open IPOM repair was per-formed in 16 Sprague Dawley rats and two minipigs.SIS implants were 2 3 2cm in rats (one per animal)and 6 3 8cm in pigs (four per animal). All implantswere fixed with six nonresorbable sutures. Observa-tion period was 17 and 28 d (n [ 8) in rats and 28 d inpigs. Outcome parameters were assessed macroscopi-cally, and histologic samples (H and E staining) wereobtained.

Results. Upon autopsy, SIS appeared to be only mod-erately integrated. Dislocation of five SIS implants intheratsandoftwoSISimplants inthepigswereobservedalthough all sutures were still in place. No seroma forma-tion or infection was detected macroscopically, but sub-stantial shrinkage and adhesion formation at themargins of implants and suture sites were frequently ob-served. Histology confirmed the macroscopic finding oflimited integration and substantial shrinkage. The path-omorphology was similar in both species.

1 To whom correspondence and reprint requests should beaddressed at Department of Visceral Surgery, Wilhelminenspital,Vienna, Austria, Montleartstrasse 37, A-1171-Vienna. E-mail: [email protected].

2 These two authors contributed equally to this study.

0022-4804/$36.00� 2010 Elsevier Inc. All rights reserved.

264

Conclusions. Small intestine submucosa implantsare susceptible to shrinkage, dislocation, and adhesionformation in experimental IPOM repair in rats andpigs. These findings are in accordance with literatureand warrant further investigations of SIS implants inhernia repair. � 2010 Elsevier Inc. All rights reserved.

Key Words: porcine small intestine submucosa;experimental IPOM; shrinkage; adhesions.

INTRODUCTION

Intraperitoneal onlay mesh repair (IPOM) has be-come a standard procedure for the repair of incisionalhernias [1, 2]. Although this technique has obvioustechnical advantages, including tension-free repairand laparoscopic detection of occult, multiple hernias,it can be associated with some adverse effects such asadhesion formation, mesh infection or shrinkage. Thesynthetic IPOM meshes most commonly used aremade of polymers, often layered with absorbable anti-adhesive barriers [3–5]. Along with refined mesh tech-nologies, the atraumatic fixation of meshes, for examplewith fibrin sealant (FS) contribute to reducing compli-cations in IPOM [6].

Recent literature suggests the potential benefits of bi-omeshes. Biomeshes can be divided into two main cate-gories. First, products derived from animal sources,e.g., porcine small intestine submucosa (SIS; Surgisis,Cook, Bloomington, IN), porcine cross linked collagen(PCL; PermaCol, Covidien, Aldershot, UK) and bovinepericard (TuM; Tutomesh, Tutogen, Neunkirchen, Ger-many) [7–11]. Implants processed from decellularizedhuman cadaveric skin (AD; Alloderm, KCI, Branch-burg, NJ) form a second category of human allografts

Page 2: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

PETTER-PUCHNER ET AL.: SMALL INTESTINE SUBMUCOSA IN EXPERIMENTAL IPOM 265

[12, 13]. The large number of related experimental andclinical studies on SIS, PCL, and AD reflect their wide-spread distribution in the clinical arena in North Amer-ica. The assumption that biological materials provokeless foreign body reaction (translating to less associatedadverse effects), yield better biocompatibility comparedwith synthetic competitors, and serve as biodegradablematrices for tissue ingrowth, could not be reproduced inour own experimental trials [14, 15]. In actual fact, theacceptance of these biomeshes for clinical incisional anddiaphragmatic hernia repair is based on results ofrather small trials [16, 17].

Most clinical reports have so far failed to provide nec-essary histologic data although distinct complicationsof biomeshes (e.g., transcutaneous exposure of PCL im-plant, shrinkage of SIS, and antibody formation to SIS)associated with the implantation of biomeshes havebeen described [15, 16, 18]. SIS has already been testedin our lab in a model of experimental onlay hernia re-pair [15]. This study was designed to assess safetyand efficacy of SIS implants as allo- or xenografts in ex-perimental IPOM repair, and to elucidate the contro-versial discussion [7, 11, 15, 19–21]. The observationperiods in this study were based on findings from recentpublications, and chosen to detect tissue integrationand adhesion formation at an early stage, as well aspersisting complications, such as implant shrinkageand dislocation [20–24].

MATERIALS AND METHODS

Male Sprague-Dawley rats, weighing 400–450 g, were obtainedfrom the Institut fuer Labortierkunde und genetik der MedizinischenFakultaet der Universitaet Wien (Himberg, Austria). Female mini-pigs, weighing 18–27 kg, were obtained from Ellegard Company, Aar-hus, Denmark. The Surgisis IHM implant (SIS; four perforatedlayers, Cook) was purchased from the local distributor. All reagentsused were of analytical grade, and surgery was performed under ster-ile conditions. The study protocol was approved by the authority of thecity government of Vienna.

Group Randomization

Sixteen rats were randomized to group 1 (17 d observation period;n¼ 8) or group 2 (28 d\ observation period; n¼ 8). Minipigs wereoperated in group 3 (28 d; n¼ 2).

Implant Size

SIS implants were precut to a 2 3 2 cm in rats and 6 3 8 cm in pigs,and preoperatively (preOP) hydrated with saline. The sizes of the im-plants were fitted to the anatomical and technical requirements, i.e.,adequate distance to wound margins, no overlap of implants in pigs,and an explantation without mechanical damage to the samples.

Surgical Model

The described procedure in rats and pigs mimics intraperitoneal on-lay mesh repair, in which the implant is placed intra-abdominally on

the intact peritoneum and attached to the abdominal wall by means ofperforating fixation devices.

Surgery in Rats

Rats (n¼ 16) were anaesthetized with an intramuscular injection ofKetavet (ketamine-hydrochloride 100 mg/mL; Pharmacia, Erlangen,Germany) and Rompun (xylazine-hydrochloride; Bayer, Leverkusen,Germany).

The abdomen was thoroughly shaved and skin desinfection per-formed. Subsequently, the skin was incised with a scalpel and the sub-cutaneous fat tissue was bluntly detached from the abdominalmuscles. A U-shaped laparotomy was made in the epigastral levelfrom left to right, beginning and ending about 1.5 cm under the lateralrib cage. The abdominal wall was flipped caudally and the peritoneumexposed, allowing a direct view of the implant site. SIS was placed onthe peritoneum in a midline position with a distance of at least 1 cmbetween the implant margins and the incision. SIS was suturedwith six stitches of nonresorbable suture material (Synthofil 4/0; Ethi-con, Norderstedt, Germany). The mesh was sutured at all four cornersand in the middle of the lateral margins in rats. Special attention wasdevoted to a reproducible suture technique with stitches placed 4 to5 mm towards the centers of the SIS implants in order to achieve a se-cure grip of the SIS matrix. The skin incision was closed in anatomicallayers, and 1 mL of physiologic saline was administered subcutane-ously to compensate for dehydration.

Postoperative Care of Rats

The rats were kept in single cages during the remaining observa-tion periods, and were checked daily for signs of infection, seroma for-mation, or abscess formation. Analgesic treatment was routinelysupplied once daily for 3 d postoperatively (postop; intramuscular ap-plication of Temgesic, buprenorphine; Merck, Vienna, Austria; 2 mg/kg bodyweight).

Surgery in Pigs

Anesthesia in pigs was induced with a cocktail (1 mL per kg body-weight) of Zoletil 100 (tiletamine 250 mg/zolazepam 250 mg; VirbacLab., Carros, France), Rompun (xylazine; Bayer, Leverkusen, Ger-many), and Ketamidor (ketamine hydrochloride; Richter Pharmaka,Wels, Austria). Thiopental (0.5 mL thiopental-Na 2.5%; Sandoz,Kundl, Austria) was administered intravenously to facilitate intuba-tion. General anesthesia was established with isofluran (Abbott,Kent, UK), and Alloferin (alcuronium; ICN Pharmaceuticals, Frank-furt/M., Germany) was used for relaxation. Atropine (atropinum sul-furicum; Nycomed, Vienna, Austria, 0.5 mg) as well as a single shot ofPeni-Strepto antibiotic (penicillin G 50 000 IU; Virbac Lab., Carros,France) were delivered perioperatively. A midline laparotomy of ap-proximately 20 cm in length was performed and four SIS were im-planted per animal bilaterally to the midline in the upper andmiddle abdomen. All implants were fixed with six nonresorbable su-tures (Synthofil 2/0, Ethicon, Norderstedt, Germany). The mesh wassutured at all four corners and in the centre of the long margins ofthe implants (8 cm) with stitches placed 7 to 8 mm towards the centersof the SIS implants. The incision was closed in anatomical layers.After application of a wound dressing, anesthesia was ended, andthe pigs were allowed to recover in single compartments.

Postoperative Care of Pigs

The pigs were closely observed for 72 h postop, and were examineddaily by a veterinarian for signs of disturbed wound healing or infec-tion. If necessary, the wound dressing was renewed and analgetictreatment, consisting of Metacam 20 mg/mL (meloxicam, 1 mL/50 kgbodyweight; Intervet, Vienna, Austria) was routinely administered.

Page 3: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

JOURNAL OF SURGICAL RESEARCH: VOL. 161, NO. 2, JUNE 15, 2010266

After 3 d, the animals were transferred to an approved longtermhousing facility. Animals were routinely weighed and examined twotimes per week.

Autopsy of Rats

Two of the rats operated in the 28 d group died within 48 h postop.Postop bleeding into the abdominal cavity was verified as cause ofdeath in one rat; the operating field showed no complications in thesecond animal at autopsy. The remaining 14 rats were sacrificed asscheduled on the 17th (n¼ 8, group 1) and 28th (n¼ 6, group 2) daypostop under anaesthesia by an i.v. injection of 1 mL of thiopental(1 g; Sandoz, Kundl, Austria).

Autopsy of Pigs

The minipigs (group 3) were sacrificed on the 28th postop day. Gen-eral anesthesia was induced as described, and the minipigs were eu-thanized by intravenous administration of T61 (drug foreuthanasia-combined of embutramid 200 mg, mebezonium 50 mg,and tetracain 5 mg per mL; Intervet, Vienna, Austria).

Observation Periods

Observation periods were chosen to assess early adhesion forma-tion (17 d in rats) and persisting complications, e.g., dislocation andshrinkage, 4 wk postop, in order to spare animals from unnecessarysuffering.

Macroscopy

Seroma formation, signs of local inflammation, and tissue integra-tion were independently assessed by two investigators blinded togroup assignment (AHP, NW). These macroscopical parameters aregenerally accepted in experimental hernia research [3, 14, 15, 25, 26].

The score is based on an A (no), B (modest), to C (severe alteration)scale, and has already been reliably used in studies on bio- and syn-thetic meshes [14].

Seroma Formation

Absence of seroma was scored as A, a seroma (encapsulation withfluid) closely adjacent to the implant was scored as B, and massive‘‘bubble-like’’ swelling as C.

Local Inflammation

No visible inflammation (defined as unfavorable inflammation withpus and debris) was scored as A, small amounts of debris and pus werescored as B, and abscess formation as C.

Tissue Integration

Complete integration of the whole implant (tissue ingrowth and vas-cularization visible to the naked eye) was scored as A, an implant onlypartly integrated (less than 50% of surface area) was scored as B,whereas no detectable integration (e.g., no tissue penetration throughperforation holes, edges of the implant not integrated) was scored as C.

Dislocation

Dislocation was defined as visible detachment of the implant fromthe underlying abdominal wall. The implant found in its original po-sition with all four edges adjacent to abdominal wall was scored as A,an implant with up to 30% of its surface area detached was scored asB, any dislocation more severe (>30% to free-floating in the abdomi-nal cavity) was scored C. The failure of a suture knot led to a scoringof A in favor of the implant material.

Shrinkage

A shrinkage of less than 10% of the original size was scored A, 10%to 30% as B, and >30% as C. If the local situation prevented the scor-ing of a parameter, it was rated X (not definable).

Adhesions

Adhesions were scored in rats according to the score first describedby Vandendael [27] (Appendix 1).

Histology

After macroscopical evaluation, all samples were fixed in 10% buff-ered formaldehyde solution (Merck, Vienna, Austria) and embeddedin paraffin. Five micrometer (mm) sections were stained with H andE. Blinded analysis and grading for the following parameters wereperformed (WO).

� Macrophages� Lymphocytes and plasma cells� Foreign body reaction (as defined as prolonged neutro-

phil response, foreign body giant cells and necrosis)� Tissue integration based on neovascularization and fi-

broblast ingrowth through the perforation holes or thematrix of the implant

Histologicl Grading

0 indicated¼ no, 1¼moderate, 2¼ strong, and 3¼maximum alter-ation in comparison with tissue of native rats. This histologic gradingsystem has also been previously used in our own studies [15].

RESULTS

Macroscopy in Rats and Minipigs

The observation period was unremarkable in all ani-mals. Two rats in group 2 died prior to the intended endof the experiment. No wound infection or superficialsigns of implant migration were observed.

There were no indications for a species-specificresponse to SIS. The exuberant granuloma formationpreviously encountered with SIS in the onlay positionwas not observed in rats in this study [15]. Macroscopi-cal results are summarized in Table 1.

Seroma Formation and Local Inflammation (group 1, 2, and 3)

No seroma formation was detected in any animal.

Group 1 (17 D Observation Period; n [ 8 Rats)

Tissue Integration and DislocationThe tissue integration was markedly impaired in

group 1. In five rats, less than 50% of the surface ofSIS was integrated and scored B. Nevertheless, thesewere the samples that were still found in the originalposition at autopsy, and were not dislocated (A). Inthree rats, no macroscopical signs of tissue integrationwere observed (C). These samples showed no signs of fi-broblastic ingrowth or neovascularization, and theedges of the implants were not incorporated into the un-derlying abdominal wall. They were attached to the ab-dominal wall by only one suture (n¼ 2), or freelyfloating in the abdominal cavity (n¼ 1), resulting inan insufficient score for dislocation (C). All sutures

Page 4: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

TABLE 1

Scores of Macroscopical Outcome Parameters

Species Seromaformation

Localinflammation

Tissueintegration

Dislocation Shrinkage Adhesionformation

Rat 17 dGroup 1

A A 5B/3C 5A/3C 4A/4C 2: I2: II4: III

Rat 28 dGroup 2

(þ¼Death of animals)

A A 6B/2þ 4A/2C/2þ 4A/2C/2þ 2: I4: III2:þ

Minipig 28 dGroup 3

A A 6B/ 2C 6A/2 C 6A/ 2B 0: I2: II6: III

Two rats in group 2 died for unknown causes prior to the scheduled time point of assessment (¼þ). The number of implants are given forevery outcome parameter. A ‘‘letter only’’ signifies that all implants within a group received the same scoring for this specific parameter,e.g., good results (A) for seroma formation and local inflammation in all three groups. If samples were scored differently for a parameterthen the number of animals is followed by the score, e.g., 5B/3C for tissue integration in group 1 means that five rats were scored B and threerats were scored C. In short description, the score A reflects a good, the score B a only moderate, and the score C a nonfavorable result for thefollowing parameters: seroma formation, local inflammation, tissue integration, dislocation and shrinkage. The scoring of the adhesion forma-tion was performed according to an algorithm published by Vandendael (Appendix 1). This scoring system of macroscopical parameters andadhesions has been repeatedly published. The precise definitions are listed in the Methods section. The summarized findings show problematicaspects concerning dislocation and shrinkage of SIS in all groups. Species specific differences could not be assessed and were not directly tested.

PETTER-PUCHNER ET AL.: SMALL INTESTINE SUBMUCOSA IN EXPERIMENTAL IPOM 267

were intact but had cut through the SIS matrix. Theseresults indicate the importance of early tissue integra-tion of the implant in order to prevent dislocation.

ShrinkageFour SIS in group 1 shrunk less than 10% (A),

whereas four SIS shrunk more than 30% (C). Impor-tantly, all dislocated meshes showed substantialshrinkage. It seems likely that shrinkage played an im-portant role in the dislocation scenario and contributedto the fact that the sutures cut through.

Adhesion FormationTwo SIS in group 1 were rated I for mild adhesion for-

mation in the Vandendael score (Appendix 1). Two SISwere scored II reflecting moderate adhesions, and fourSIS showed severe adhesions (III), mostly originatingfrom mesh margins and sutures (Fig. 1). The scoringof adhesions according to the algorithm suggested byVandendael is based on a set of four parameters: width,thickness, strength, and amount of adhesions [27] (Ap-pendix 1). Moderate and severe adhesions correspondto clinically relevant adhesions in humans (great num-ber and/or not bluntly dissectible). These adhesionswould not dissolve in the early postop phase of our ani-mal model and persisted for at least 28 d (see results ofgroup 2).

FIG. 1. SIS showed only moderate susceptibility to adhesion for-mation in the samples that did not dislocate or shrink. However, ad-hesions originated from mesh margins and sutures (filled arrows),and tissue integration was restricted to perforation holes after 17 din rats (dotted area). (Color version of figure is available online.)

Group 2 (28 D Observation Period; n [ 8 Rats, 2 Dropouts)

Tissue Integration and DislocationIn all animals surviving the full observation period

(n¼ 6), SIS appeared only partly integrated, and were

rated B. This rating indicates that more than 50% ofthe surface of SIS was bare of fibroblastic ingrowth, vas-cularization, or signs of tissue integration to the nakedeye (Fig. 1). This finding is clearly inferior to our find-ings with synthetic meshes in the same animal model[28]. In terms of dislocation, four out of six SIS werefound in the original position and scored A for disloca-tion, whereas two were adjacent to the liver and weredislocated, elicting severe adhesions (C; Fig. 3).

Page 5: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

FIG. 2. In this figure, a SIS implant is shown in a pig 4 wk after sur-gery. The margin of the implant caused severe and broad adhesions,while sutures remained intact (dotted arrow). One suture connectsthe otherwise free floating implant to the peritoneum (filled arrow).On close inspection of the puncture holes, it seemed likely that the af-fected sutures cut through. The finding of dislocated SIS was similarin rats and pigs. (Color version of figure is available online.)

JOURNAL OF SURGICAL RESEARCH: VOL. 161, NO. 2, JUNE 15, 2010268

ShrinkageFour SIS were scored A because they retained their

original size (<10% shrinkage). Similar to group 1,the two dislocated SIS shrunk to less than a third oftheir original size, and were scored C.

Adhesion FormationTwo implants elicited mild adhesions (I), whereas

four implants (including the dislocated samples) eli-cited severe adhesions (III). The pattern of these severeadhesions was comparable to findings in group 1, withsutures and margins of SIS triggering their formation.

Group 3 (28 D; n [ 2 Minipigs with Four SIS Implanted

Per Animal)

Tissue Integration and DislocationTissue integration was impaired to less than 50% of

the surface area of six SIS and scored B (3 SIS per mini-pig). One SIS per minipig was completely integratedand scored A. Two SIS were free-floating in the abdom-inal cavity and scored C for dislocation (one SIS in eachminipig; Fig. 2). Four SIS stayed in place (A).

ShrinkageNo shrinkage (<10%) was found in six SIS (A), and

two implants showed severe shrinkage (>30%) in the

same minipig (C). One of the shrunken SIS was com-pletely dislocated.

Adhesion FormationAdhesion formation did not seem to be influenced by

the allogenic setting. Six SIS (three per minipig) werescored III for severe adhesions to the small bowel, stom-ach, and liver. Two SIS were scored B for moderate ad-hesions. Although not directly comparable to groups 1or 2, adhesion formation to SIS in the minipig groupgenerally appeared more severe (Figs.1 and 2).

HistologyHistology confirmed the macroscopical findings of

sufficient biocompatibility but limited integration ofSIS. Parameters relevant for an unfavorable inflamma-tory response, for example:

MacrophagesLymphocytes and plasma cellsForeign body reaction was rated as 1 (moderate; n¼ 16) in all samples in rats (17 and 28 d), and pigs.The inflammatory response was substantially lesspronounced than with Surgisis Gold in the previ-ously published onlay model in rats [15].Tissue integration was rated 1 in all rats and 1 inall pigs, with minimal fibroblast ingrowth andsporadic penetration of single vessels at the perfo-ration holes after 17 and 28 d in rats and after 4wk in pigs. The histologic assessment of tissue in-tegration did not reveal evident differences be-tween species. In contrast to the well knowntransgression of tissue through the pores of syn-thetic meshes implanted in the intraperitonealonlay position, the surface area of SIS appearedstrictly inpenetrable in histologic evaluation, con-firming macroscopic findings [28]. The histopatho-morphologic picture did not reveal differences inthe use of allo- or xenograft in rats or pigs (Figs.3, 4, and 5).

DISCUSSION

This study was designed to provide experimentaldata on implant ingrowth and adhesion formation ofSIS in experimental IPOM repair in rats and pigs. Sec-ondary endpoints of interest were shrinkage and dislo-cation. Although SIS can be considered as one of themost widely investigated biomeshes, important aspectsremain poorly understood [15, 20]. A recent publicationby Ansaloni et al. reported the postop formation of hu-man antibodies against SIS implants, but denied anyclinical relevance [29]. In our opinion, this is a contro-versial finding, signifying a classic foreign body reac-tion and not the favourable host acceptance proposed

Page 6: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

FIG. 3. Dislocated SIS was adjacent to the liver in two rats ingroup 3 (28 d observation period). This histologic picture shows twoimportant features of the adverse effects encountered with SIS in ex-perimental IPOM. First, shrinkage of the SIS implant, and second,adhesion formation, which were both frequent, especially in dislo-cated implants. The dotted circle marks the SIS implant, and the ar-row points at the border zone between SIS and liver parenchyma,which could only be dissected with sharp instruments. (Color versionof figure is available online.)

PETTER-PUCHNER ET AL.: SMALL INTESTINE SUBMUCOSA IN EXPERIMENTAL IPOM 269

by the authors. We suggest, on the contrary, that thisphenomenon actually helps to explain the severe com-plications, e.g., shrinkage, impaired integration, recur-rences, and the need for explantation reported inclinical and experimental studies [15, 20, 24, 30].

This study was a sequel to our own experiments withSIS in an experimental onlay model in rats [15]. Chronicabdominal wall defects, accurately mimicking inci-sional hernias, were covered with SIS, resulting in ab-scess formation, shrinkage, and dislocation after 17 d.The paper was published in 2006 in Surgical Endoscopyand was fiercely debated [31]. Consequently, various

FIG. 4. This histologic overview of a SIS implant in a rat 28 d postopout the double polarizing reflections of the suture material, indicating ttissue. The yellow circle is placed in the large gap between the large p(full yellow arrows). The mesh is not yet integrated but only encapsulat

studies were published, which encouraged us to testSIS intra-abdominally in experimental IPOM repair,and to adopt some important modifications to the studydesign [14–16, 32].

First, it was decided to implant the thinner SIS IHM,which consists of only four perforated layers of small in-testine submucosa (versus eight nonperforated layers ofthe SIS Gold) [32]. We followed the recommendation ofDr. Morales-Conde, who found similar adverse effects,i.e., granulomatous inflammation, with SIS Gold im-plants in a pilot trial in pigs. Light weight and macro-porosity are broadly discussed parameters forimproved tissue integration of synthetic mesh mate-rials, and seemed equally beneficial in this trial [33].

Second, the porcine SIS was implanted in pigs in or-der to rule out adverse effects triggered by xenogenic-ity. It should be emphasized, however, that theimplantation in rats is closer to the clinical xenograft‘‘reality’’.

The most prominent findings in this study of experi-mental IPOM were shrinkage and dislocation of SIS(Figs. 1, 2, and 3). Although shrinkage is a commonlyperceived phenomenon of virtually any hernia meshmaterial, the current understanding is that the syn-thetic materials do not shrink, but the surroundingscar tissue (meshoma) does. In this context, we pointout that there is unanimous evidence from in vitroand in vivo trials that the SIS matrix per se shrinks,and that this process is characterized by a significantreduction of the surface area of the implant in short ob-servation periods, comparable to the time period in thisstudy [18, 24, 34]. We suggest that shrinkage playeda key role in the dislocation of SIS in this trial, andcould possibly lead to an increased risk of clinical recur-rences due to the loss of overlap.

underlines the macroscopic observation. The broad black arrow pointshe small areas of full contact of the SIS implant with the underlyingart of the SIS implant (dotted black arrows) and the abdominal walled (dotted yellow arrow). (Color version of figure is available online.)

Page 7: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

FIG. 5. This histologic sample shows a SIS implant 4 wk after im-plantation in a pig. No substantial differences to the findings in ratsare observed, especially, tissue integration was not markedly im-proved, neither was the inflammatory reaction less pronounced. Theblack arrows point out the SIS implant, the red arrow marks the ac-cumulation of granulomatous cells. The four layered matrix of themesh is hardly entered by any fibroblasts or vessels. (Color versionof figure is available online.)

JOURNAL OF SURGICAL RESEARCH: VOL. 161, NO. 2, JUNE 15, 2010270

Recurrences after SIS implantation for the treatmentof abdominal wall defects in humans were reported bythe study group of Gupta et al. who also demonstratedimpaired tissue integration histologically in explantedSIS specimens [24, 35]. In the largest clinical trialaddressing the issue, the study group of Franklinet al. recently published good results with SIS for her-nia repair in infected or potentially contaminated fieldsin a large cohort of patients (n ¼ 116) and provided his-tology from six uncomplicated cases [15]. Unfortu-nately, the histologic data presented in this studymust be considered inconclusive because of the lack ofboth predefined outcome parameters as well as manda-tory information, e.g., the chosen staining method. Thestated overall recurrence rate of less than 8% in thesehigh risk patients seems extremely low, given the factthat the author concludes that SIS was fully degradedat 5 y postop. The low rate of recurrences could partlybe explained by the fact that 35% of patients (n ¼ 38)in this trial had been primarily operated for umbilicalhernias [15]. Mr. Franklin admits that recurrenceswere most often seen in large incisional hernias andcontaminated wounds, and although details are notlisted, it is noteworthy to remark that the recurrencerate for this patient population was closer to 15%–20%.

In our studies, the impaired tissue integration of SISwas evaluated microscopically, following the standardsthat have demonstrated their reproducibility in ourprevious publications (Figs. 4 and 5) [28]. SIS washighly susceptible to adhesion formation and not supe-rior to synthetic meshes when results were comparedusing the same animal model [28].

The pattern of adhesions revealed the crucial role ofperforating fixation devices and mesh margins as ‘‘hotspots’’ of adhesion formation (Figs. 1 and 2) [36–38].The definition of herniosis as a generalized disease ofthe connective tissue may demand nonresorbable andpermanent meshes [15, 39]. Keeping these aspects inmind, long-term complications associated with thetreatment of abdominal wall defects and hiatal herniarepair with SIS remain possible [30, 40].

CONCLUSION

We conclude that future experimental trials are man-datory to fully elucidate the biocompatibility of SIS inIPOM repair. We are aware of the limitations of ourstudy, but we are convinced that it serves as an impor-tant and valid contribution to the ongoing debate on SIS.

ACKNOWLEDGMENT

The authors thank James Crawford Ferguson and Christopher Mayfor revision of the manuscript.

APPENDIX 1

Score by Vandendael

Scoring points Parameter Criteria

1

Width, mm <2 2 2–10 3 >10 1 Thickness, mm <1 2 1–3 3 >3 1 Strength þ 2 þþ 3 þþþ 1 Amount 0–2 2 3–4 3 >4 Grade I (mild) 1–4 Grade II (moderate) 5–8 Grade III (severe) 9–12

REFERENCES

1. Lomanto D, Iyer SG, Shabbir A, Cheah WK. Laparoscopic versusopen ventral hernia mesh repair: a prospective study. Surg En-dosc 2006;20:1030.

2. Bingener J, Buck L, Richards M, et al. Long-term outcomes inlaparoscopic versus open ventral hernia repair. Arch Surg2007;142:562.

3. Burger JW, Halm JA, Wijsmuller AR, et al. Evaluation of newprosthetic meshes for ventral hernia repair. Surg Endosc 2006;20:1320.

4. Huschitt N, Feller M, Lotspeich E, et al. [Open intraperitonealhernia repair for treatment of abdominal wall defects–Early re-sults by placement of a polypropylene-ePTFE-mesh]. ZentralblChir 2006;131:57.

Page 8: Small Intestine Submucosa (SIS) Implants in Experimental IPOM Repair

PETTER-PUCHNER ET AL.: SMALL INTESTINE SUBMUCOSA IN EXPERIMENTAL IPOM 271

5. Schug-Pass C, Tamme C, Tannapfel A, et al. A lightweight poly-propylene mesh (TiMesh) for laparoscopic intraperitoneal repairof abdominal wall hernias: comparison of biocompatibility withthe DualMesh in an experimental study using the porcine model.Surg Endosc 2006;20:402.

6. Olmi S, Scaini A, Erba L, et al. Laparoscopic repair of inguinalhernias using an intraperitoneal onlay mesh technique and a Pa-rietex composite mesh fixed with fibrin glue (Tissucol). Personaltechnique and preliminary results. Surg Endosc 2007;21:1961.

7. St Peter SD, Ostlie DJ, Holcomb GW, III. The use of biosyntheticmesh to enhance hiatal repair at the time of redo Nissen fundo-plication. J Pediatr Surg 2007;42:1298.

8. Fine AP. Laparoscopic repair of inguinal hernia using Surgisismesh and fibrin sealant. JSLS 2006;10:461.

9. Ansaloni L, Catena F, Gagliardi S, et al. Hernia repair withporcine small-intestinal submucosa. Hernia 2007;11:321.

10. Armellino MF, De Stefano G, Scardi F, et al. [Use of Permacol incomplicated incisional hernia]. Chir Ital 2006;58:627.

11. Catena F, Ansaloni L, Gazzotti F, et al. Use of porcine dermal col-lagen graft (Permacol) for hernia repair in contaminated fields.Hernia 2007;11:57.

12. Bellows CF, Albo D, Berger DH, et al. Abdominal wall repair us-ing human acellular dermis. Am J Surg 2007;194:192.

13. Gaertner WB, Bonsack ME, Delaney JP. Experimental evalua-tion of four biologic prostheses for ventral hernia repair. J Gas-trointest Surg 2007;11:1275.

14. Petter-Puchner A, Fortelny R, Walder N, et al. Adverse effectsassociated with the use of porcine cross linked collagen implantsin an experimental model of incisional hernia repair. J Surg Res2007;145:105.

15. Petter-Puchner AH, Fortelny RH, Mittermayr R, et al. Adverseeffects of porcine small intestine submucosa implants in experi-mental ventral hernia repair. Surg Endosc 2006;20:942.

16. Parker DM, Armstrong PJ, Frizzi JD, et al. Porcine dermal col-lagen (Permacol) for abdominal wall reconstruction. Curr Surg2006;63:255.

17. Espinosa-de-los-Monteros A, de la Torre JI, Marrero I, et al.Utilization of human cadaveric acellular dermis for abdominalhernia reconstruction. Ann Plast Surg 2007;58:264.

18. Poulose BK, Scholz S, Moore DE, et al. Physiologic properties ofsmall intestine submucosa. J Surg Res 2005;123:262.

19. Wisbach G, Peterson T, Thoman D. Early results of the use ofacellular dermal allograft in type III paraesophageal herniarepair. JSLS 2006;10:184.

20. Helton WS, Fisichella PM, Berger R, et al. Short-term outcomeswith small intestinal submucosa for ventral abdominal hernia.Arch Surg 2005;140:549.

21. Kim H, Bruen K, Vargo D. Acellular dermal matrix in the man-agement of high-risk abdominal wall defects. Am J Surg 2006;192:705.

22. Rauth TP, Poulose BK, Nanney LB, et al. A comparative analysisof expanded polytetrafluoroethylene and small intestinal sub-mucosa–Implications for patch repair in ventral herniorrhaphy.J Surg Res 2007;143:43.

23. Poulose BK, Scholz S, Moore DE, et al. Physiologic properties ofsmall intestine submucosa. J Surg Res 2005;123:262.

24. Gupta A, Zahriya K, Mullens PL, et al. Ventral herniorrhaphy:Experience with two different biosynthetic mesh materials, Sur-gisis and Alloderm. Hernia 2006;10:419.

25. Garcia-Urena MA, Vega RV, Diaz GA, et al. Differences in poly-propylene shrinkage depending on mesh position in an experi-mental study. Am J Surg 2007;193:538.

26. Elliott MP, Juler GL. Comparison of Marlex mesh and micropo-rous teflon sheets when used for hernia repair in the experimen-tal animal. Am J Surg 1979;137:342.

27. Vandendael A, Struwig D, Nel JT, et al. Efficacy of fibrin sealantin prevention of adhesion formation on ovar surgical wounds inrabbit model. Gyn End 1996;1:169.

28. Petter-Puchner AH, Walder N, Redl H, et al. Fibrin sealant (Tis-sucol) enhances tissue integration of condensed polytetrafluoro-ethylene meshes and reduces early adhesion formation inexperimental intra-abdominal peritoneal onlay mesh repair.J Surg Res 2009.

29. Ansaloni L, Cambrini P, Catena F, Saverio SD, Gagliardi S,Gazzotti F, Hodde JP, Metzger DW, D’Alessandro L,Pinna AD. Immune response to small intestinal submucosa (sur-gisis) implant in humans: Preliminary observations. J InvestSurg 2007;20:237.

30. St Peter SD, Valusek PA, Tsao K, et al. Abdominal complicationsrelated to type of repair for congenital diaphragmatic hernia.J Surg Res 2007;140:234.

31. Catena F, Ansaloni L, D’Alessandro L, et al. Adverse effects ofporcine small intestine submucosa (SIS) implants in experimen-tal ventral hernia repair. Surg Endosc 2007;21:690.

32. Gagliardi S, Ansaloni L, Catena F, et al. Hernioplasty with Sur-gisis(R) Inguinal Hernia Matrix (IHM)trade mark. Surg TechnolInt 2007;16:128.

33. Conze J, Rosch R, Klinge U, et al. Polypropylene in the intra-abdominal position: influence of pore size and surface area. Her-nia 2004;8:365.

34. Amid PK. Radiologic images of meshoma: A new phenomenoncausing chronic pain after prosthetic repair of abdominal wallhernias. Arch Surg 2004;139:1297.

35. Franklin ME, Jr., Trevino JM, Portillo G, et al. The use of por-cine small intestinal submucosa as a prosthetic material for lap-aroscopic hernia repair in infected and potentially contaminatedfields: Long-term follow-up. Surg Endosc 2008;22:1941.

36. Martin-Cartes J, Morales-Conde S, Suarez-Grau J, et al. Use ofhyaluronidase cream to prevent peritoneal adhesions in laparo-scopic ventral hernia repair by means of intraperitoneal meshfixation using spiral tacks. Surg Endosc 2008;22:631.

37. Olmi S, Addis A, Domeneghini C, et al. Experimental compari-son of type of Tissucol dilution and composite mesh (Parietex)for laparoscopic repair of groin and abdominal hernia: Observa-tional study conducted in a university laboratory. Hernia 2007;11:211.

38. Joels CS, Matthews BD, Kercher KW, et al. Evaluation of adhe-sion formation, mesh fixation strength, and hydroxyproline con-tent after intra-abdominal placement of polytetrafluoroethylenemesh secured using titanium spiral tacks, nitinol anchors, andpolypropylene suture or polyglactin 910 suture. Surg Endosc2005;19:780.

39. Jansen PL, Mertens PP, Klinge U, Schumpelick V. The biology ofhernia formation. Surgery 2004;136:1.

40. Desai KM, Diaz S, Dorward IG, et al. Histologic results 1 yearafter bioprosthetic repair of paraesophageal hernia in a caninemodel. Surg Endosc 2006;20:1693.