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

Abstract

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. 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. 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. 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. On the basis of these findings, the Krackow stitch remains the preferred method for suture fixation of soft-tissue grafts.