The Effect of Varying Throws in Three Suture Techniques for Tendon Graft Fixation- A Biomechanical Study

Purpose: Biomechanically evaluate the optimal number of throws for achieving graft-holding capacity of currently used suture techniques. Methods: Porcine flexor profundus tendons randomly divided into 9 groups of 11 specimens were used. Three stitch configurations, namely the Krachow stitch, locking SpeedWhip (LSW) stitch and modified finger trap (MFT) suture, were assessed with 3, 5 and 7 throws. The Krackow stitch and MFT suture were completed with a No. 2 FiberWire suture (Arthrex), while the LSW stitches were completed with a loop of No. 2 FiberWire suture (Arthrex). Each tendon was pre-tensioned to 100 N for three cycles and then cyclically loaded to 200 N for 200 cycles. Finally, each tendon was loaded to failure. Percent elongation, load to failure, and mode of failure for each suture-tendon construct were measured. Results: After being pre-tensioned, there were no significant differences in the elongation between different suture throws in the LSW and MFT suture groups (p= 0.38 and 0.34). The elongation of the 7-throw group in the Krackow suture group was significantly larger than the 5-throw group (p= 0.01) and 3-throw group (p= 0.03). After cyclic loading, there was no significant difference in the elongation of each suture technique, with respect to different suture throws. The elongation after 200 loading cycles of the MFT sutures was significantly less than the Krackow sutures and LSW sutures for the 3, 5, and 7-throw. The load to failure and cross-sectional area were not significantly different across all suture groups. Conclusion: This study showed that there are no significant differences in the elongation after cyclic loading and loads to failure among the various suture throws in any of the tested suture configurations. Clinical Relevance: The 3-suture throw configuration may provide sufficient fixation of the tendon graft with regard to biomechanical characteristics of elongation and load to failure.