Biomechanical comparison of different fixation methods on the tibial side in anterior cruciate ligament reconstruction: a biomechanical study in porcine tibial bone

Background. The fixation strength of the hamstring tendon graft on the tibial side is considered the weak point in anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the biomechanical characteristics of four types of ACL reconstruction methods on the tibial side. Methods. Extensor digitorum tendons harvested from fresh bovine forelimbs were used as the graft materials in this study. Twenty-eight porcine tibias were divided into four groups based on different fixation methods. Group D was fixed using a double spike plate (DSP), group I was fixed using an interference screw, group DI-80 was fixed using both an interference screw and DSP (80N tension was applied to DSP), and group DI-150 was fixed using both an interference screw and DSP (150N tension was applied to DSP). Results. The displacement of the grafts in response to 500 cycles of 0-150N loading was significantly greater in groups D (10.3 +/- 15mm) and I (5.5 +/- 1.7mm) than that in groups DI-80 (2.1 +/- 0.3mm) and DI-150 (1.2 +/- 0.4mm), with no significant differences between groups DI-80 and DI-150. The ultimate failure load and stiffness were significantly higher in groups DI-80 (745 +/- 156N, 103 +/- 17N/mm) and DI-150 (801 +/- 129N, 151 +/- 35N/mm) than those in groups D (374 +/- 53N, 70 +/- 13N/mm), and I (520 +/- 76N, 78 +/- 18N/mm). The stiffness of group DI-150 was significantly greater than that of group DI-80. Conclusions. Our results indicate that the initial fixation strength of the hamstring tendon can be increased by using an interference screw combined with DSP on the tibial side.