Effect of the Optimal Asymmetry on the Strength of Six-Strand Tendon Repair: An Ex Vivo Biomechanical Study

Purpose To evaluate the mechanical properties of a 6-strand core suture repair with asymmetric purchase in the 2 tendon ends, in comparison with a repair with symmetric suture purchases. Methods Under cyclic loading of the tendons, we recorded the fatigue strength (Forces × Cycles) of a 6-strand flexor tendon repair with different symmetry in the lengths of suture purchase in 60 porcine tendons. The symmetric repair was made with 3 groups of parallel Kessler repairs of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps, and shifting 2 other Kessler repairs by 1, 2, 3, 4, or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair. Results The core repairs with 2 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly greater fatigue strength compared with those with symmetric suture placement. The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly smaller gaps compared with those with symmetric suture placement. Conclusions The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends generated increased fatigue strength and reduced gap sizes compared with those with symmetric suture placement in an ex vivo porcine model. Clinical relevance An asymmetric core suture repair with 3 mm or more difference in purchase length may allow for earlier rehabilitation and reduce the risk of postoperative complications.