Over-The-Top Knot Placement Technique Enhances Tensile Stability of Tendon Repairs

Background: Currently a major concern for the surgical treatment of Achilles tendon rupture repairs is the creation of stable enough fixation to allow early range of motion. It was documented that the weakest point in a suture loop is the knot. Thus, we hypothesized that moving the knot away from the repair junction (over-the-top Krackow technique) would increase the strength of the repair. Materials and Methods: Transected bovine tendons were repaired by the traditional Krackow and over-the-top Krackow techniques using four suture materials (Fiberwire Nos. 5 and 2, Ethibond Nos. 5 and 2). Tendons were cyclically tested at incremental loads beginning from 50 N until 5-mm gap formation. Then all tendons were loaded to failure. The number of cycles to 5-mm gapping, ultimate failure loads and knot slip were compared using t-test and Mann-Whitney tests (with Tukey corrections for multiple comparisons). Results: Mean number of cycles to 5-mm gapping did not reveal significant differences (p = 0.113) between repair groups. Mean failure load of tendons repaired by over-the-top Krackow technique were significantly higher (p < 0.0001) for all four paired groups than tendons repaired by traditional Krackow technique. Ethibond No. 5, No. 2, and Fiberwire No. 2 suture repairs with over-the-top configuration did not reveal any knot slip. Conclusion: Over-the-top Krackow technique increases the ultimate failure load of repaired tendons. But 5-mm gapping resistivity was not enhanced either by the technique or the suture material. Clinical Relevance: The knot itself is a stress-riser in the suture loop so we suggest that freeing it from tension by our modificiation may achieve more durable repairs.