Biomechanical comparison of shoelace suture technique for repairing calcaneal tendon

Background: The biomechanical assessment of tendon repair is essential for the evaluation of different tendon suturing techniques. The shoelace suture technique with absorbable Vicryl (R) is a modified technique of Achilles tendon repair that may have biomechanical advantages depending on the number of threads used and the direction of the suture. Purpose: To evaluate the creep under constant pre-load, the stiffness, the maximum strength, and the failure mode for three different configurations of the shoelace suture in a bovine tendon biomechanical model. Study design: Controlled Laboratory Study. Methods: 36 bovine Achilles tendon specimens were acquired and divided into three test groups of 12 Achilles tendons each. A model of the calcaneal tendon rupture was created through a transverse cut with a scalpel, performed 5 centimeters proximal to the calcaneal bone insertion. Group 1 was repaired using the simple shoelace technique with just one suture. Group 2 was repaired using the shoelace technique with three sutures individually sutured from distal to proximal at the site of rupture. Group 3 was repaired using the shoelace technique with three sutures individually sutured from proximal to distal at the site of rupture. Results: System creep after constant pre-load was 5.9 +/- 2.5 mm, 3.0 +/- 0.4 mm and 2.9 +/- 0.4 mm for groups 1, 2 and 3, respectively. The system's stiffness was 23.2 +/- 2.8 N/mm, 30.3 +/- 1.1 N/mm and 29.8 +/- 2.3 N/mm for groups 1, 2 and 3, respectively. In the final load-to-failure test, the ultimate load force (ULF) was 158.2 +/- 27.5 N, 346.5 +/- 47.6 N and 358.1 +/- 41.6 N for groups 1, 2 and 3, respectively. There was statistical significance in the comparative tests between groups 1-2 and 1-3 in terms of means of creep, system stiffness and maximum system strength. No statistically significant difference was found between groups 2 and 3 when analyzing creep, system stiffness and ULF. Suture breakage was the prevalent mode of failure for all tested groups. Conclusion: The shoelace with three sutures significantly reduced creep in the preloading phase and increased the stiffness and ultimate load force. The biomechanical results demonstrate better overall mechanical performance of the technique than the simple shoelace technique. The better mechanical performance indicates that the shoelace with three sutures could result in early postoperative rehabilitation. Clinical relevance: This study indicates that the shoelace suture technique with three sutures is biomechanically strong and stiff, being a possible therapeutic option to be used.