Poster P16 - Mechanical Characterization of Porcine Dura Mater under Uniaxial Tension

Introduction: Traumatic brain injury is one of the significant causes of death in the United States, making up ~30% of all injury-related deaths. In the clinical setting, understanding the underlying mechanisms of the head injury is essential to treat patients with these types of injuries. There are currently a multitude of physical and computational brain injury models that are used to study the underlying mechanisms of traumatic brain injury, but these models often neglect the dura mater's role in mitigating these types of injuries. Therefore, this study provides region specific mechanical properties of porcine dura mater to help with informing brain injury models with increased fidelity.

Materials and

Methods: Cranial dura mater used in this study was harvested from three female pigs (24-72 hours post-mortem). Immediately after dissection, the tissue was flash-frozen in an isopentane solution and stored at -80°C. When ready for testing, the samples were thawed at 4°C for 24 hours and then brought to room temperature in a phosphate-buffered saline (PBS) solution. Dog-bone shapes were retrieved from the anterior (x3), lateral (x2), and posterior (x3) regions of the dura mater using a customized cutter. Samples were tested at a strain rate of 0.3 mm/s along the anterior-posterior direction. Small sections to either side of the gauge length were saved in a separate vial of PBS to measure the tissue thickness. Thickness was measured by creating impressions with a light-cure adhesive and measuring the depth of the impression with a caliper. The samples were then loaded into the Mach1 (Biomomentum, QC, Canada) V500C for tensile testing, and a 2-camera Vic3D (Correlated Solutions, South Carolina, USA) system was used to analyze local strain. A custom MATLAB code was generated to synchronize the imaging and mechanical data and to locate the linear regions of the resultant curves.

Results, Conclusions, and Discussions:

Results:
The linear region for the anterior, lateral, and posterior regions were in strain ranges between 3.3-8.8%, 3.1-5.8%, and 2.3-10.2%, respectively. Linear regression was performed on the linear region to obtain the following Young’s Modulus values: anterior = 38.4 ± 15.7MPa, lateral = 72.6 ± 17.4MPa, posterior = 14.1 ± 3.00MPa. The ultimate tensile strengths (UTS) were anterior = 4.02 ± 1.45MPa, lateral = 4.51 ± 0.511MPa, posterior = 2.34 ± 0.994MPa. The average thickness for each region were anterior = 0.306 ± 0.083mm, lateral = 0.213 ± 0.071mm, posterior = 0.37 ± 0.009mm.

Conclusions:
A one-way ANOVA test at significance level α = 0.05 revealed that the Young’s modulus values of the regions were significantly different. The lateral region exhibited the stiffest properties, followed by the anterior and then posterior regions. Another one-way ANOVA test at α = 0.05 revealed that the UTS was also significantly different.

Discussion:
Youngs modulus and UTS vary across dura likely due to the functional roles of the tissue in the three different regions. This information could serve as valuable input for designing and developing region-specific dura implants for post-surgery use. The regional difference in mechanical properties found in this study can also be used to develop more accurate physical and computational brain injury models for clinical use. To further add on to these models, the viscoelastic and anisotropic properties should also be evaluated.

Acknowledgements (Optional): The authors would like to thank the University of Florida Animal Care Services for the tissue donation. Research reported was supported by the National Institute of Neurological Disorders and Stroke of the National Institutes of Health under award number R01NS122939.