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.

Do adipofascial flaps affect the mechanical properties of a repaired tendon? A biomechanical rat model study.

The aim of this study was to evaluate the effect of vascularized and non-vascularized fascial flaps on tendon healing, specifically the maximum strain, maximum stress, elasticity and resistance of the repaired tendon. Rats were randomly divided into 3 groups: Group 1 - primary repair; Group 2 - vascularized pedicled fascial graft; Group 3 - non-vascularized free fascial graft. The rats were euthanized after 2 weeks and 40mm-long samples were taken from the Achilles tendon and gastrocnemius muscle. To evaluate the mechanical properties of the tendons, maximum load, maximum deformation, energy stored until yield point and stiffness on the load-deformation curve were measured. Based on this mechanical testing, the best group in terms of tissue strength and quality was the primary repair group. When the samples were examined individually, the two samples with the highest breaking force after the control group were in the pedicled graft group. The worst results overall were in the free graft group. We believe that if the blood flow is preserved for the fascial flap in the pedicled graft group, the tendon's breaking force would be higher.