Biomechanical analysis of a new 8-strand technique for flexor tendon repair

We sought to compare the strength and rupture sites of a new 8-strand suture technique with those of an established 6-strand flexor tendon repair through biomechanical analysis. This new 8-strand suture pattern places minimal suture material in the remodeling zone and focuses on protecting the knot, a well-known weak point of the suture construct. The knot was buried within the tendon so as to not interfere with tendon gliding. In a biomechanical simulation, strength and rupture sites were compared with those of the 6-strand repair. We repaired a total of 54 porcine flexor tendons using one of the two techniques (n=27 each). Tensile strength at 2-mm gap formation and ultimate failure load were determined. Afterwards, we dissected the tendons to identify the rupture site of the suture material. The new 8-strand suture had a significant higher ultimate load to failure (87.7N) and 2-mm gap load (71.6N) compared to the 6-strand technique (57.7N and 45.9N) (P<0.001). Whereas the rupture site of the core suture in the 6-strand technique was mainly located next to the knot (81.5%), the suture seemed to fail independently from this weak spot in the 8-strand technique (11.1%). This new 8-strand technique achieves a strong flexor tendon repair in a biomechanical model. Additional cross-locking on either side of the knot seems to contribute to the repair's strength. The resulting higher ultimate failure load and 2-mm gap load may allow more aggressive active motion-based postoperative rehabilitation.