Background: Our hypothesis that multiple, equally tensioned strands of hamstring graft used for reconstruction of the anterior cruciate ligament are stronger and stiffer than ten-millimeter patellar ligament grafts was tested biomechanically with use of tendons from cadavera. Methods: In the first part of the study, we measured the strength and stiffness of one, two, and four-strand hamstring grafts, from fresh-frozen cadaveric knees, that had been tensioned equally when clamped. In the second part of the study, we compared four-strand grafts to which tension had been applied by hand and then clamped with similar grafts to which tension had been applied with weights and then clamped. The grafts for the two experiments were obtained from thirtyfour paired and ten unpaired knees. We also studied the effects of cooling on the biomechanical properties of grafts by comparing patellar ligament grafts tested at 13 degrees Celsius with those tested at room temperature. Results: Two equally tensioned gracilis strands had 185 percent of the strength and 210 percent of the stiffness (1550 ± 428 newtons and 336 ± 141 newtons per millimeter, respectively) of one gracilis strand (837 ± 138 newtons and 160 ± 44 newtons per millimeter, respectively). Two equally tensioned semitendinosus strands had 220 percent of the strength and 220 percent of the stiffness (2330 ± 452 newtons and 469 ± 185 newtons per millimeter, respectively) of one semi-*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding sources were the

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