Hydrated vs. freeze-dried human acellular dermal matrix for hernia repair: A comparison in a rabbit model

Background: Abdominal wall hernias commonly occur following laparotomy. Biologic grafts are used to treat these hernias due to their biocompatibility and their ability to serve as a matrix for tissue regeneration and remodeling. Freeze-dried human acellular dermal matrices (F-HADMs) have been shown to be effective in abdominal wall defect repair. Hydrated human acellular dermal matrices (H-HADMs) have not been previously evaluated. This study evaluates H-HADM and F-HADM in the repair of abdominal wall hernias in the rabbit. Methods: Thirty-six3-4-kg New Zealand white rabbits underwent laparotomy with the creation of a hernia. After defect reperitonealization, the animals underwent hernia repair with H-HADM, F-HADM, or primary repair. Within each group, four animals were survived for 4, 8, and 20 weeks. The outcomes evaluated included recurrences, adhesions, histology, immunohistochemistry, and tensiometry. Results: Thirty-five animals underwent abdominal wall hernia repair. One animal in the F-HADM group developed a recurrent hernia. No significant difference was demonstrated in adhesion scores between the H-HADM (0.75) and F-HADM (0.83) groups. Tensiometry demonstrated no differences in the forces required to disrupt the graft from the native fascia between H-HADM and F-HADM at any time point. H-HADM demonstrated fewer white blood cells (WBC) and eosinophils (EOS) per high-powered field (hpf) than F-HADM at 4 weeks (144 WBC/hpf vs. 534 WBC/hpf, P <0.05; 87 EOS/ hpf vs. 304 EOS/hpf, P <0.05) and 8 weeks (104 WBC/hpf vs. 314 WBC/ hpf, P <0.05; 41 EOS/hpf vs. 149 EOS/hpf, P <0.05). At 20 weeks, there was no difference in WBC or EOS (134 WBC/hpf vs. 144 WBC/hpf, P = NS; 86 EOS/hpf vs. 104 EOS/hpf, P = NS). Immunohistochemistry for CD31 demonstrated no difference in vascularity at any time point. Conclusions: H-HADM and F-HADM demonstrate comparable results in abdominal wall hernia treatment in a rabbit model. With both grafts, the weakest area of the repair occurs at the graft and native fascia interface. Hernia repairs with H-HADM and F-HADM demonstrate similar incidences of adhesions and tensile strength characteristics. H-HADM demonstrates a reduced inflammatory response at 4 and 8 weeks compared to F-HADM. Both H-HADM and F-HADM demonstrate similar amounts of vascular ingrowth.