A Biomechanical Comparison of Modified Krackow and Locking Loop Suture Patterns for Soft-Tissue Graft Fixation

PURPOSE: The purpose of this ex vivo biomechanical study was to evaluate the tensile mechanical properties of 2 modified suture-graft constructs regarding elongation after pre-tensioning and cyclic loading as well as load to failure.

METHODS: Thirty fresh-frozen porcine Achilles tendons were randomly divided into 2 groups of 15 specimens to assess elongation of the suture-graft construct across 2 different tendon-grasping techniques: a modified locking SpeedWhip (MLS) stitch and a modified Krackow (MK) stitch. Each tendon was pre-tensioned to 89 N for 10 minutes and then cyclically loaded to 200 N for 200 cycles. Finally, each tendon was loaded to failure.

RESULTS: After being pre-tensioned, the MK group elongated significantly more than the MLS group (7.12 ± 0.95 mm v 6.26 ± 0.94 mm, P = .02). Elongation after cyclic loading for the MK and MLS groups was not significantly different (3.39 ± 0.95 mm and 3.21 ± 0.93 mm, respectively; P > .05). The MK group showed a significantly larger load to failure compared with the MLS group (689 ± 61 N v 604 ± 46 N, P = .000024). The mean tendon cross-sectional area was larger in the MK group (399 ± 5 mm(2)v 393 ± 8 mm(2), P = .02), but this difference did not relate to the amount of elongation or load to failure. All but 1 specimen failed by suture breakage at the square knot.

CONCLUSIONS: The MLS and MK stitches, pre-tensioned to 89 N for 10 minutes, both effectively minimized suture-graft construct elongation after cyclic loading. Consequently, both suture patterns are recommended for soft-tissue graft fixation.

CLINICAL RELEVANCE: The MLS and MK suture configurations may provide sufficient biomechanical fixation of the tendon graft in the clinical setting of soft-tissue fixation without an interference screw.