Biomechanical evaluation of an allograft fixation system for ACL reconstruction

Abstract

The purpose of this study was to compare the biomechanical stability, especially graft slippage of an allograft screw and a conventional interference screw for tibial implant fixation in ACL reconstruction. Twenty-four paired human proximal tibia specimens underwent ACL reconstruction, with the graft in one specimen of each pair fixed using the allograft screw and the other using the conventional interference screw. Specimens were subjected to cyclic tensile loading until failure. The two fixation methods did not show any statistical difference in load at graft slippage (p = 0.241) or estimated mean survival until slippage onset (p = 0.061). The ultimate load and the estimated mean survival until failure were higher for the interference screw (p = 0.04, and p = 0.018, respectively). Graft displacement at ultimate load reached values of up to 7.2 (interference screw) and 11.3 mm (allograft screw). The allograft screw for implant fixation in ACL reconstruction demonstrated comparable behavior in terms of graft slippage to the interference screw but underperformed in terms of ultimate load. However, the ultimate load, occurring at progressive graft slippage, may not be considered a direct indicator of clinical failure.

The Development and Biomechanical Analysis of an Allograft Interference Screw for Anterior Cruciate Ligament Reconstruction

“…Compared to the previous study analyzing the biomechanical stability of the allograft interference screw in human proximal tibia specimens [40], the ultimate failure load measured here is higher (235.08 ± 88.54 N compared to 174.9 ± 82.9 N). Again, this was to be expected, as bovine or porcine models tend to over estimate ultimate failure load of the graft fixation, hence the results achieved of in vitro animal models cannot be directly transferred to a clinical setting [47].…”

“…The observed mean insertion torque of the interference screw during graft fixation was 1125 ± 369.58 N mm and, therefore, slightly higher than the insertion torque of 822 ± 289 N mm reported in a recent study analyzing the biomechanical stability of the allograft interference screw in human proximal tibia specimens [40]. This was to be expected, since the insertion torques in bovine bone are generally higher than in human bone [41].…”