Repair of oronasal fistulas with human amniotic membrane in minipigs

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Abstract

We evaluated the use of multilayer human amniotic membrane (HAM) as a grafting material for the repair of mid-palate oronasal fistulas in seven Berlin minipigs. After two weeks, three animals had the fistulas repaired with multilayered HAM grafts, three had them repaired with a collagen-based dermal substitute (INTEGRA®, Integra Life Sciences, Plainsboro, NJ, USA), and one fistula was left untreated to serve as a control. Grafts were interposed between the oral and nasal mucosa, traversing the fistulas. After healing for 40 days, the pigs were killed for clinical, histological, and immunohistochemical examination.

Two of the three fistulas closed with HAM were successful, the diameter of the third was reduced in size, and there was no change in the diameter of the fistula in the control.

This study shows successful closure of oronasal fistulas in minipigs using interposed grafts of cryopreserved HAM, and offers promise as a simple and effective technique for tension-free closure of such fistulas.

Introduction

The formation of an oronasal fistula is a serious complication of the primary repair of cleft palates. Its incidence varies widely, ranging from 0% to 68% in published reports.1 Many causes have been proposed for the formation of a fistula after repair of a cleft palate, including paucity of local tissue for closure, and excessive scarring.1, 2, 3, 4, 5 Various techniques for repair have been suggested including local2 and free flaps,3 tissue expansion,4 and the use of allogenic tissues and biomaterials.1, 5

Fresh human amniotic membrane (HAM) has been used for nearly a century in reconstructive surgery,6 but its use in developed countries has been limited by the risk of cross-infection. The introduction of a method for glycerol-cryopreservation allowed donors and tissue to be retested after the “infection window”, and HAM transplantation became a regular procedure in ophthalmological operations.7 Ophthalmological studies advocated the use of the tissue for its low immunogenicity, minimal inflammation and scarring, and enhancement of epithelialisation.8 Its success in ophthalmology as an adjunct in wound healing encouraged its use in extraocular, immunogenic tissue. Oral and maxillofacial surgeons have described its use for gingival wound healing,9 intraoral lining in vestibuloplasty,10, 11 and in the prefabrication of flaps.12 To overcome shortcomings in mechanical stability, Kruse et al. proposed a multilayered application for deep corneal defects.13 In vivo studies have shown that defects in the abdominal wall can be closed successfully with cryopreserved multilayered HAM.14 We evaluated the use of multilayered HAM as a grafting material for the repair of oronasal fistulas in minipigs.

Section snippets

Materials and methods

We used seven male six-month-old Berlin minipigs (Fa. Schlesier, Großerkmannsdorf, Germany), weighing 22–31 kg (mean 25.8) each. They were kept according to the international principles of laboratory animal care. Water and food were given freely. The study was approved by the local ethics committee and the local government.

Human placentas were obtained under sterile conditions from planned, uneventful Caesarean sections. All women had given written informed consent. A 5 cm × 5 cm piece was prepared

Results

The fistula of the untreated control had epithelialised wound margins, and it had decreased to 13 mm. Two of the three HAM-covered fistulas remained closed with no visual evidence of a remaining fistular tract (Fig. 3). The diameter of the third HAM-covered fistula had been 3 mm on day 9 and 6 mm on day 40. All the fistulas treated with INTEGRA® dehisced and had a significantly larger diameter than those treated with HAM on day 40 (p = 0.043) (Table 1). Interestingly, all wounds treated with INTEGRA®

Discussion

Formation of scars and a shortage of tissue complicate the repair of oronasal fistulas. Current methods for their closure can be broadly divided into four groups that use local mucoperiostal flaps, pedicled flaps such as from the tongue, free flaps such as from the forearm, and biomaterials. Donor site morbidity can be substantial so biomaterials seem ideal, but until now none have fulfilled the complex requirements of biocompatibility and integration.

HAM and its extracellular matrix contain

Acknowledgements

We thank Andrea Rittig for technical assistance. This work was supported by the medical faculty of the Ruhr University Bochum (FoRUM, F321/01).

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    • Cited by (0)

    1

    Both authors contributed equally to this work.

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    Copyright © 2009 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.