Dermal graft thickness over 2mm and grafts oriented parallel to skin tension lines increased graft strength and suture retention: a biomechanical study.

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The purpose of this study is to assess the variability in graft biomechanical properties of an acellular human dermal matrix patch. A total of 22 strips obtained from 6 separate graft specimens (AlloPatch HD) were tested. Load elongation properties after cyclic loading including ultimate load at break, energy at break and extension at break were tested, and compared by graft thickness. Suture pull-out testing using a simple vertical stitch suture retention test was performed. There was a significant, strong positive correlation between graft thickness and ultimate load to failure, energy at break, and extension at break (p<0.01). The association between direction of graft in relation to skin tension lines and ultimate load to failure was also significant (p< 0.034) The difference in ultimate load to failure from the extremes of graft thickness in this study (1.1 mm versus 3.2mm) was almost four-fold (104 N/mm2 versus 402 N/mm2). The suture pull-out testing of 10 dermal graft test strips demonstrated that once the graft thickness reaches a threshold thickness of 2mm, the mode of failure changed from cutting through the graft vertically to tearing the graft diagonally CONCLUSION: The tested dermal allograft patch shows great variability in thickness within and between individual patches. This study has demonstrated that grafts thicker than 2mm and those used in parallel to skin tension lines exhibit a higher ultimate load to failure. Furthermore, graft thickness over 2mm influenced the method of suture failure.