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Method Article
This manuscript describes methods associated with creation and repair of a ventral abdominal wall defect (hernia). This model can be used to study repair strategies such as those that use implanted materials. In this manuscript, repair of the experimental hernia with porcine small intestinal submucosa is presented as an example.
Ventral abdominal hernia is a relatively common clinical condition that sometimes requires herniorraphy (surgical repair). The repair of ventral abdominal hernia typically requires implantation of a material to serve as a mechanical bridge across the defect in the abdominal wall. Biomaterials, such as porcine small intestinal submucosa (SIS), also serve as a lattice for cell growth into the implant and can naturally incorporate into the host tissue. Development of such repair materials benefits from use of animal models in which experimental abdominal wall defects are easily created and are amenable to repair in a reproducible fashion. The method offered here describes surgical creation and repair of ventral abdominal hernia in a rat model. When SIS is used to repair an experimental ventral abdominal hernia in this model, it is rapidly incorporated into host tissue within 28 days of implantation. Histologically, incorporation of their implanted material into host tissue is characterized by a robust fibrovascular response. Future refinements and applications of the rat abdominal hernia model may likely involve diabetic and/or obese animals as a means to more closely mimic common co-morbidities of man.
Abdominal wall hernia is a commonly encountered clinical issue which may occur as a result of congenital defect, traumatic injury, or failed closure of surgical wounds involving the abdominal wall. Repair commonly involves using an implant to reinforce the abdominal wall, with a reduced rate of recurrence noted in patients treated with an implant compared to those in whom the abdominal wall is simply closed with suture.1
Surgical hernia repair often requires mechanical bridging of the defect with an implanted material. In this regard, both synthetic and natural materials have been used for hernia repair. Many synthetic materials are typically non-absorbable and include polypropylene, polyethylene terephthalate polyester, and expanded polytetrafluoroethylene, while other synthetic implants combine one of the non-absorbable materials with an absorbable polymer such as polygalactine.1 In contrast, natural material implants are generally derived from either animal or human cadaveric sources. Natural materials used for hernia repair are typically rich in collagen and act as a scaffold for ingrowth and integration of host tissue.
The desire to develop and optimize new materials for ventral abdominal hernia repair requires an appropriate animal model for evaluation of candidate materials. Studies have been conducted in a variety of species, including sheep,2 pigs,3 rabbits,4 rats,5,6,7,8 and dogs.9 The advantage of using rats for such studies is that they offer an easily handled model available in a variety of inbred strains to allow for control of genetic variability. In addition, the smaller overall body surface area of the rat compared to the other species listed above permit evaluation of materials that may be experimental in nature and, therefore, not abundant. Further, reduced costs associated with rats versus other species allow for relatively increased ability to screen candidate materials for use in repair of ventral abdominal hernia. Considerations for materials typically include ease of handling by the surgeon, strength, ability to incorporate into host tissue, biocompatibility, and resistance to infection.
As an example, porcine small intestinal submucosa (SIS) is a natural biomaterial that has been used for a wide variety of tissue repair indications, including repair of ventral abdominal, inguinal, and diaphragmatic hernias.10,11,12 SIS is rapidly incorporated into host tissue and has been found to be generally resistant to infection and so the material has particular utility in contaminated fields.13,14 In the rat model, SIS has demonstrated ease of handling, good tensile strength as determined by the uniaxial tensile failure test, and promotion of tissue ingrowth in terms of collagen deposition and neovascularization.6,7
Accurate surgical bridging of the defect is an essential feature of productive modeling when evaluating candidate repair materials. The animal must be sufficiently anesthetized and aseptic technique strictly followed. Further, an abdominal wall defect of standard size must be carefully created and then bridged in a manner that sufficiently secures the material to the margins of the defect.8 This protocol provides a standard method to be followed for surgical creation, and repair of, a ventral abdominal hernia using SIS as an example bridging material in a rat.
The use of animals in this protocol was approved by the University of Notre Dame Institutional Animal Care and Use Committee, followed all regulatory requirements and guidelines, and was conducted in a facility that is accredited by the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC), International.
1. Selection of Animals
2. Anesthesia and Preparation of Animal for Aseptic Surgery
3. Creation and Repair of the Ventral Abdominal Hernia
4. Harvest of the Implanted Material
By 28 days after implantation, SIS typically demonstrates good incorporation into host tissue (Figure 2). In most cases, there is residual SIS apparent, though the tissue must often be explored to identify the implanted material. Histological analyses confirmed the gross pathological observations, illustrating good tissue incorporation with primarily fibrovascular tissue and very little residual SIS noted (Figure 3). These results demonstrate the utility ...
Materials for the repair of ventral abdominal hernia are of great interest, particularly those that provide an initial mechanical bridge and are then able to incorporate into host tissue. In this regard, a variety of materials have been investigated, including SIS, porcine acellular dermal matrix, and porcine pericardium.6,7 These materials represent the extracellular matrices of those tissues and act as scaffolds into which cells can migrate and proliferate, thu...
One of the authors (CJ) is employed by Cook Biotech, Inc., the manufacturer of medical grade SIS.
The authors wish to thank Valerie Schroeder for her assistance with technical aspects of this work. Work related to development of this model was supported by Cook Biotech, Inc. (West Lafayette, IN USA).
Name | Company | Catalog Number | Comments |
Isoflurane (Isoflo) | Henry Schine Animal Health | 17579 | gas anesthetic |
Optixcare Eye Lubricant | Henry Schine Animal Health | OPX4240 | Ocular lubricant |
Oster clippers | Henry Schine Animal Health | 6092 | hair clippers |
Betadine surgical scrub | Henry Schine Animal Health | 1618 | antiseptic iodophor |
Sterile scalpel | Henry Schine Animal Health | 329 | #10 scalpel |
9" x 12" disposable surgical drape | Braintree Scientific, Inc. | SP-RPS | Surgical drape |
4-0 nylon suture | Braintree Scientific, Inc. | SUT 812 | Suture material |
4-0 Absorbable Suture | Henry Schine Animal Health | 29242 | Synthetic absorbable suture |
9 mm Autoclips and applier | Braintree Scientific, Inc. | ACS KIT | Surgical staples for closure of skin incision |
Torbugesic/analgesic | Henry Schine Animal Health | 12084 | Butorphanol tartarate for post-operative analgesia |
Small intestinal submucosa (SIS) | Cook Biotech, Inc. | Implant material for bridging experimental abdominal wall defect | |
Rats | Harlan, Inc. | Sprague Dawley | Animal for hernia modeling |
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