A biomechanical comparison of 4-strand and 5-strand anterior cruciate ligament graft constructs

Hamstring tendon autografts are used for reconstruction of the anterior cruciate ligament. This study tested the hypothesis that a 5-strand hamstring autograft construct is superior in strength to a 4-strand construct. Four-strand and 5-strand tendon grafts constructs were prepared from ovine flexor tendons and then tested in a uniaxial electromechanical load system with suspensory fixation. The 4-strand and 5-strand constructs were pre-conditioned, stressrelaxed and loaded to ultimate failure. Stress-relaxation, stiffness and ultimate load were compared using a one-way ANOVA. There were no statistical differences in stress-relaxation, initial stiffness, secondary stiffness or ultimate load between 4-strand and 5-strand split tendon graft constructs. Inconsistent failure patterns for both 4-strand and 5-strand constructs were observed. The additional strand in the 5-strand construct may be shielded from stress with additional weakness secondary to the use of suspensory fixation. The potential biological benefit of religamentization and bony integration, with more autologous tissue in the intra-articular space and bony tunnels remains unknown.