Dermal Graft Thickness Over 2 mm and Grafts Oriented Parallel to Skin Tension Lines Increased Graft Strength and Suture Retention: A Biomechanical Study.

Purpose: To assess the variability in graft biomechanical properties of an acellular human dermal matrix patch.

Methods: 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.

Results: There was a significant, strong positive correlation between graft thickness and ultimate load to failure, energy at break, and extension at break (P < .01). The association between direction of graft in relation to skin tension lines and ultimate load to failure was also significant (P < .034). The difference in ultimate load to failure from the extremes of graft thickness in this study (1.1 mm vs 3.2 mm) was almost 4-fold (104 N/mm vs 402 N/mm). The suture pull-out testing of 10 dermal graft test strips showed that once the graft thickness reached a threshold thickness of 2 mm, the mode of failure changed from cutting through the graft vertically to tearing the graft diagonally.

Conclusions: The tested dermal allograft patch shows great variability in thickness within and between individual patches. This study has revealed that grafts thicker than 2 mm and those used in parallel to skin tension lines exhibit a higher ultimate load to failure. Furthermore, graft thickness over 2 mm influenced the method of suture failure.

Clinical Relevance: Caution should be exercised when using grafts less than 2 mm due to lower ultimate load to failure and suture pull-out. Marking the patches in accordance with skin tension lines would help determine the ideal orientation of insertion.