1. Department of Bioengineering SUTURE PERFORMANCE 102 A Gyong Min Bak – Background & Hypothesis Heather Forquer – Methods & Protocol Kelvin Leung – Deliverables George Scangas – Pitfalls & Equipment & Budget

2. Department of Bioengineering Background: Past findings show that the interrupted stitch sutures resist deformation better than the running locked sutures. However, the results were found using a constant force for a short period of time. These parameters do not give an appropriate measure of how the sutures would perform in tissue under more dynamic conditions, such as a changing force applied until failure. Objective & Hypothesis: The objective of the experiment is to evaluate the performance of an interrupted stitch suture in chicken skin, assuming that an inadequate suture will significantly alter the Young’s modulus and fracture force in samples. The central hypothesis is that these properties will be significantly different between intact samples and composites (sutured chicken skin), revealing that the interrupted stitch suture method is not adequate. Gyong Min Bak

3. Department of Bioengineering Methods & Protocol: Prepare 8 chicken skin samples (1.6 x 2.0”). Keep samples moist. Prepare 5 more samples of equal dimension. Cut in half with scalpel and suture using 3 interrupted stitches, 0.4” apart and 0.25” in from the severed edge. Calibrate Instron using 0.5 & 1kg. Set crosshead speed to 50 mm/min. Use three intact samples as surrogates to determine data acquisition parameters. Before clamping, wrap a piece of sandpaper over the ends of the sample, placing the rough side toward the skin. Test all samples. Record force vs. displacement values, noting slippage and location and geometry of failure. Calculate Young’s Modulus and fracture force for all samples, using reproducible mathematical methods. Use a two-tailed t-test to compare these values for the intact and sutured samples. Heather Forquer

4. Department of Bioengineering Proposed Deliverables/Findings: Expected data calculated from the force vs. displacement graph (example to the right) will give the Young’s Modulus and fracture force. The Young’s Modulus is the slope of the initial linear portion of the curve, which will be defined mathematically. We expect the p-value of the t-test to be less than 0.05, showing a significant difference between the Young’s Modulus and fracture force for sutured and intact skin. Kelvin Leung

5. Department of Bioengineering Potential Pitfalls: One potential problem is the slippage of samples out of the clamps before failure. Using sandpaper to increase the friction between sample and clamp reduces this possibility. However, cross head speed may need to be adjusted if samples or composites continue to slip. Another issue is an immediate failure of composite upon force loading. This would lead to an inadequate amount of data to be analyzed to find the Young’s Modulus and failure force. If this occurs, the amount of stitches and/or distance of suture from the edge of the sample may need to be adjusted. George Scangas

6. Department of Bioengineering Equipment/Materials and Budget & Justification: Equipment: These items are essential for performing the experiment. Instron 4444 Scalpel, cutting board, tweezers, scissors Caliper, ruler Weight set (0.5 & 1 kg) Supplies: Sandpaper needed to increase friction between chicken skin sample and Instron clamps. Sutures needed to more effectively imitate actual sutures. Perdue chicken thighs – 2 packages, approximately $7/package Norton 9 in. X 11 in. Coarse Sandpaper (25 Pack) - $13.35 Supplier: www.homedepot.com Monofilament Sutures, 6/0 Black Monofilament CP MEDICAL Suture, 18" w/ NC-2 - $28.80 Supplier: www.medicalsupply4sale.com George Scangas