This study was conducted to clarify the influence of cyclic displacement on the structural properties of four types of femur-graft-tibia complexes used to reconstruct the anterior cruciate ligament. Forty hindlimbs from pigs were used. In two groups, bone-patellar tendon-bone grafts were secured with interference screws (group A) or the suture-post technique (group B). In two groups, multistrand flexor tendons were fixed using the tape-staple technique (group C) or the sutures-tied-over-a-button technique (group D). In each group, five femur-graft-tibia complexes underwent tensile failure tests without cyclic displacement. The other five complexes underwent 5000 cycles of cyclic elongation for 2 mm, and then underwent the tensile failure tests. The initial stiffness significantly decreased after cyclic displacement in each group, although there were no significant differences in the linear stiffness and the ultimate failure load between the tests with and without cyclic displacement. These findings suggest that 5000 cycles of repetitive elongation of the femur-graft-tibia complex by 2 mm does not jeopardize the graft fixed with the procedures used in this study, despite a slight but significant increase of an anterior-posterior laxity of the knee.

Considering the tension of the normal anterior cruciate ligament (16 to 87 N), an initial tension of 20 N appears to be high enough for a patellar tendon graft. For a flexor tendon graft with interference screws, an increase in initial tension above 80 N has no biomechanical advantages.

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