Introduction: This study compares the performance of a commonly used synthetic implant, expanded polytetrafluoroethylene (DualMesh® Plus, W.L. Gore Associates, Flagstaff, AZ) to human acellular dermal matrix (AlloDerm®, LifeCell Corporation, Branchburg, NJ) for repair of lateral chest wall defects in rabbits. The study was also designed to evaluate whether human acellular dermal matrix is able to revascularize within the dynamic environment of the thorax. Methods: Seventeen rabbits were randomly assigned to one of two repair groups: expanded polytetrafluoroethylene (ePTFE) (n=8) or human acellular dermal matrix (ADM) (n=9). All animals received a 3cm x 3cm full-thickness right lateral chest wall defect and were then repaired with one of the two materials. At twenty-eight days the animals were euthanized and the following endpoints were analyzed: (a) incidence of herniation; (b) presence and tenacity of adhesions between the graft and the lung; (c) presence or absence of fluid collections overlying the graft; and (d) various biomechanical measures including the strength of the patch-fascial interface, the strength of the native contralateral chest wall, and a comparison of the tensile strength of the explanted AlloDerm® to AlloDerm® which had been re-hydrated but never implanted. Additionally, one AlloDerm® animal underwent fluorescein dye infusion to assess for graft vascularization. Tissue was sent for histological analysis and immunohistochemical evaluation of extracellular matrix composition and vascular content. Results: There was no incidence of herniation or dehiscence for either graft material. Adhesions between the graft and the lung occurred for all sites repaired with ePTFE (8/8) and in most of the sites repaired with ADM (8/9). Use of a previously described grading scale for abdominal adhesions indicated that the adhesions between the ePTFE and the lung tended to be stronger than the adhesions formed to ADM . Seromas were found overlying three of the nine ADM grafts and two of the eight ePTFE grafts. Tensiometric testing demonstrated that the mean breaking strength of the ADM -fascial interface (14.2 N ±8.7) was greater than the mean breaking strength of the ePTFE -fascial interface (10.0 N ±5.7) (p=0.028). These mean breaking strengths were both similar to the mean breaking strength of the rib-intercostal-rib interface of the contralateral chest (13.6 N ±5.1). Although not statistically significant, the mean breaking strength of ADM increased from 68.1 N (±16.5) to 71.0 N (±22.9) after 30 days of implantation. Fluorescein dye injection, and histology confirmed that the ADM patches repopulate with cells and become revascularized during the study. Conclusions: This study demonstrates that both ADM and ePTFE perform well for reconstuction of lateral chest wall defects in a rabbit model. The study also confirms that ADM revascularizes within 28 days of implantation as an interpositional graft for repair of lateral chest wall defects in a rabbit model. Since ADM develops a vascular supply, it may be a more appropriate choice for chest wall reconstruction when the defect site is contaminated or at high risk for infection.
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