• Raul Mayr, Christian Heinz Heinrichs, Martin Eichinger, Christian Coppola, Werner Schmoelz, and René Attal.
• Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
• Am J Sports Med. 2015 Jun 1; 43 (6): 1380-5.

BackgroundCortical button fixation at the femoral side and interference screws within the tibial bone tunnel are widely used for anterior cruciate ligament graft fixation. Using a bone socket instead of a full tunnel allows cortical button fixation on the tibial side as well. If adjustable-length loop cortical button devices are used for femoral and tibial fixation, the tendon graft has to be secured with sutures in a closed tendon loop. The increased distance of fixation points and potential slippage of the tendon strands at the securing sutures might lead to greater risk of postoperative graft elongation when compared with conventional graft preparation with tibial interference screw fixation.HypothesisCompared with an anterior cruciate ligament graft with tibial adjustable-length loop cortical button fixation, a graft with tibial interference screw fixation will show less graft elongation during cyclic loading and lower ultimate failure loads.Study DesignControlled laboratory study.MethodsGrafts with tibial adjustable-length loop cortical button fixation and grafts with tibial interference screw fixation were biomechanically tested in calf tibiae (n = 10 per group). Femoral fixation was equivalent for both groups, using an adjustable-length loop cortical button. Specimens underwent cyclic loading followed by a load-to-failure test.ResultsGrafts with screw fixation showed significantly less initial elongation (cycles 1-5: 1.46 ± 0.26 mm), secondary elongation (cycles 6-1000: 1.87 ± 0.67 mm), and total elongation (cycles 1-1000: 3.33 ± 0.83 mm) in comparison with grafts with button fixation (2.47 ± 0.26, 3.56 ± 0.39, and 6.03 ± 0.61 mm, respectively) (P < .001). While pull-out stiffness was significantly higher for grafts with screw fixation (309.5 ± 33.2 vs 185.6 ± 16.4 N/mm) (P < .001), grafts with button fixation were able to withstand significantly higher ultimate failure loads (908 ± 74 vs 693 ± 119 N) (P < .001).ConclusionGrafts with tibial adjustable-length loop cortical button fixation resulted in higher graft elongation during cyclic loading and showed higher ultimate failure loads in comparison with conventional graft preparation with tibial interference screw fixation at time zero.Clinical RelevanceThe results of this biomechanical study suggest that grafts with tibial interference screw fixation provide better knee stability at time zero because of reduced graft elongation and greater stiffness in comparison with grafts with tibial adjustable-length loop cortical button fixation.© 2015 The Author(s).

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