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Tendon Strengthening - A Cadaveric Biomechanical Study
Julien J Shine, MD1, Ann-Sophie Lafreniere, MD1, Maleka Ramji, MD, FRCSC1 and Justin Yeung, MD, FRCSC2, (1)University of Calgary, Calgary, AB, Canada, (2)Plastic and Reconstructive Surgery, ., Calgary, AB, Canada

Ligament reconstructions with tendon autografts are common procedures. Examples include scapholunate and ulnar collateral ligament reconstructions. The autografts initially provide sturdy and anatomical reductions of bones and joints. However, the constructs are known to weaken with time, causing some patients to experience inconvenient levels of pain and weakness. We therefore designed a biomechanical study to examine if intraoperative tendon modifications could strengthen these autograft reconstructions.

Materials and Methods:
All forearm flexor tendons were harvested from two male fresh-frozen cadavers. FCU, PL and FCR tendons were kept aside as pilots to fine-tune our protocol. FPL, PDS and FDP tendons were trimmed and randomly assigned to 4 groups; a control group (Group C), free of any modification; a single-strand running locking 3-0 Fiberwire® group (Group 1); a double-strand running locking 3-0 FiberWire® group (Group 2); a SutureTape® group (Group 3). All tendon samples were then subjected to a standardized tensile testing protocol, comprised of three separate components: a stress-relaxation test; a cyclical test; and an ultimate failure test.

At a steady state strain of 0.04, average peak force was 37 N for groups C, 1 and 2, and 39 N for group 3, whereas average steady-state force was 10 N for group C, and 11 N for groups 1, 2, and 3. Cyclic testing consisting of 50 cycles of 0.02 strain yielded average peak stress values during the 1st, 25th and 50th cycles of 17 N, 10 N, and 10 N for Group C; 13 N, 8 N and 7 N for Group 1; 14 N, 8 N and 8 N for Group 2; and 14N, 9 N and 8 N for Group 3. The average calculated Young's modulus for the groups C, 1, 2, and 3 were 755 mPa, 722 mPa, 587 mPa, and 574 mPa, respectively. Kruskall-Wallace, Mann-Whitney and Friedman comparison tests were completed and revealed no statistical difference between the control (C) and intervention (1, 2, 3) groups in any of the three components of our standardized tensile testing protocol.

No statistically significant differences were obtained between the control, single-strand running locking 3-0 Fiberwire®, double-strand running locking 3-0 FiberWire®, and a SutureTape® groups in Young's modulus, ultimate tensile strength, cyclic test peak stress, and stress-relax test peak stress. This suggests that augmentation of tendon with suture tape or other materials does not increase its strength or durability.

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