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Does the 5-strand-graft have superior biomechanical behaviour than 4-strand-graft during ACL reconstruction?

LEVEL OF EVIDENCE: Controlled Laboratory Study SUMMARY Purpose. This study aimed to compare the biomechanical proprieties of 4 and 5-strandgrafts. Methods. For the present study, fresh-frozen bovine common digital extensor tendons were used. Tendon grafts were prepared and sized to have a length of almost 27 cm and a cylinder 4 strand diameter of 8 mm. In half of all samples (Group A, n=12,), the graft was formed by 2 bundles duplicated around a metallic rod creating a 4-strand-tendon construct. In the other half of samples (Group B, n= 12,) 5-strand-tendon construct was created duplicating a single tendon around the rod, and tripling the other one. The grafts were preconditioned at 50 N for 10 min, followed by 1,000 cyclic loading between 50 and 250 N. Load-to-failure test was then carried out at a rate of 1 mm/s. Results. No statistically significant differences were found between two groups concerning cyclic elongation at the 500th cycle and at the final cycle. An increased stiffness was observed in the Group B during cyclic loads and at pull-out (p<0.05). Significant differences were noted at the ultimate load-to-failure between Group A (1533 ± 454 N) and Group B (1139 ± 276 N) (p< 0.05). Conclusion. This study showed that both graft construct appears to be biomechanically effective in a bovine tendon model. 5-strand-graft showed an increased stiffness and a decreased ultimate load-to-failure comparing to the 4-strand-graft construct. Biomechanically, no real benefit could be observed in the clinical setting increasing the numbers of strands used for the ACL reconstructive surgery.