Krackow Locking Stitch Versus Nonlocking Premanufactured Loop Stitch for Soft-Tissue Fixation: A Biomechanical Study

Purpose: The purpose of this study was to biomechanically compare the Krackow stitch, an established locking stitch, with a new nonlocking premanufactured stitch for soft-tissue fixation. We evaluated suture construct elongation under loading and load to failure to compare the 2 stitches. Methods: Twenty porcine Achilles tendons were randomly assigned to receive the locking Krackow stitch with No. 2 FiberWire or the nonlocking SpeedWhip stitch with No. 2 FiberLoop (Arthrex, Naples, FL). Each prepared tendon was mounted in a servohydraulic load frame, and the 2 free suture strands were knotted over the bar of the machine. Each tendon was pretensioned to 100 N to simulate the removal of slack, preloaded to 50 N to simulate tension applied clinically with suture tying over the post, and cyclically loaded at 200 mm/min to 200 N for 200 cycles. Total elongation of both suture strands was measured at each stage. Each tendon was loaded to failure. Results: During preloading, the SpeedWhip group elongated significantly more than the Krackow group (65.6 ± 22.5 mm v 14.9 ± 5.9 mm, P < .001). During cyclic loading, the SpeedWhip group also showed significantly higher elongation than the Krackow group (23.5 ± 8.7 mm v 11 ± 4.5 mm, P = .02). The load to failure for the Krackow and SpeedWhip groups was not significantly different (376.2 ± 39.8 N and 337.3 ± 103.8 N, respectively; P = .65). With load to failure, suture breakage at the knot occurred in every specimen without further pullout of the suture. Conclusions: The nonlocking stitch applied in a manner consistent with manufacturer guidelines was significantly less secure than the locking Krackow stitch in a porcine Achilles tendon model. Clinical Relevance: On the basis of these findings, the Krackow stitch remains the preferred method for suture fixation of soft-tissue grafts.