Department of Bioengineering Tendon Stiffness and Strain Distribution GROUP 4B Dipal Patel – Background & Hypothesis Joe Frey – Methods & Protocol Chrysta Irolla – Deliverables & Pitfalls Akivaga Tsingalia – Equipment & Budget

Department of Bioengineering Background: Various tendons in the body are subjected to strains that may cause them to rip. These tendons should be repaired in a way that does not limit range of motion and maintains the stiffness of an intact tendon. Additionally, previous suture testing experiments have shown that a repaired material under tension will exert strain on the sutured area. Hypotheses & Aims: The experiment’s primary aim is to assess the difference between the stiffness of sutured tendons and intact tendons. Because intact tendons distribute strain over a larger area than sutured tendons, it is expected that a sutured tendon will have a lower stiffness than that of an intact tendon. Additionally, camera images will be used to assess the distribution of strain in three regions along the length of the tendon. It is expected that the strain will be uniformly distributed in the intact tendon, while the strain will be more highly concentrated around the area of repair for the sutured tendon. Dipal Patel

Department of Bioengineering Methods & Protocol: Remove ten 4-inch tendons from chicken leg samples. Cut 5 of the 10 tendons into 2-inch pieces. Sew the five sets of torn tendons together using the sewing apparatus to create 5 evenly spaced running stitches. Make each stitch 1/2-inches in length. For the sutured tendons, place markings above and below sutured area, making two 1/2-inch lengthwise segments. Also make markings directly above and below stitches. Place markings in similar areas on intact tendons. Use the video camera to isolate the marked regions of each tendon, taking continuous images of each area upon tension application. Test five intact tendons and five sutured tendons with the Instron Model 4444 using the tensile attachment. Record data of applied force and displacement. Gather data and compare, calculating values of stiffness. Use camera images to tabulate total displacements of each section of all tendon samples. Calculate averages of each section for sutured tendons and intact tendons. Analyze data, comparing stiffness values and strains of specific segments of sutured tendons and intact tendons. Joe Frey

Department of Bioengineering Potential Pitfalls: Chrysta Irolla Problems with quantifying strain at specific sites (use camera to isolate sutured area). Difficulty with slipping of tendons within Instron clamps (place extra tendon in clamp to reduce slipping). Difficult to get consistent results without many biological samples (more funding would be required for more samples). According to a Mayo Clinic study 1, the stiffness of an intact tendon was 39.2 N/mm, while the stiffness of tendons with various suture repairs was 25.1 N/mm or less. It is expected that the experimental data will agree with these findings, and the stiffness of intact tendons will be greater than that of the sutured tendons. Proposed Deliverables/Findings: RepairStiffness (N/mm) Kessler23.6 (n=17) MK24.4 (n=18) Modified Savage24.9 (n=18) Lee23.0 (n=18) MGH24.2 (n=18) Running25.1 (n=18) No Repair39.2 (n=7) It is expected that sutured tendons will concentrate strain in the area of repair (the weakest point in the tendon), while intact tendons will evenly distribute strain. 1 Comparison of Mechanical Properties of Various Suture Repair Techniques in a Partially Lacerated Tendon ft/vol_122/iss_6/604_1.html#F4

Department of Bioengineering Equipment/Materials & Budget Justification: Supplies: Supramid suture material Rulers and calipers Marking pen Scissors Cutting board Akivaga Tsingalia Newly purchased equipment and supplies (Total Spending: $1637): Chicken legs ($26): source of tendons Supramid sutures ($75): material commonly used for repair 2 Sewing machine ($180): used for consistency in sutures 3 1/3" Progressive Scan IEEE 1394 Color XGA Camera ($1356): high resolution progressive scan camera needed for constant imaging of displacement measurements productcode%3D3312+Supramid+Pricing&hl=en&gl=us&ct=clnk&cd=2&client=firefox-a Equipment: Instron 4444 Instron 4444 tensile attachment Computer LabView program