Posterior cruciate ligament reconstruction with internal brace augmentation reduces posterior tibial translation under cyclic loading

The goal of this study was to evaluate the stiffness and resistance to elongation of an internal bracing (IB) construct in posterior cruciate ligament reconstruction (PCLR). The authors hypothesized that augmentation with an internal brace would increase construct stiffness and decrease posterior tibial translation during cyclic loading in a fresh frozen cadaveric model. Ten cadaver knees underwent PCL reconstruction with (PCLR+IB) and without (PCLR) augmentation with an internal brace and were compared with an intact PCL state. Knees were subjected to cyclic posterior drawer loading at 45 N, 90 N, and 134 N. The PCLR+IB showed significantly less tibial translation with posterior drawer loading compared with the PCLR. Posterior tibial translation measured 8.83 mm for the PCLR vs 6.59 mm for the PCLR+IB (P=.05) at 45 N posterior load. This difference remained significant at higher loads, with posterior translation of 10.84 mm and 8.44 mm for PCLR and PCLR+IB, respectively, at 90 N (P=.035) and posterior translation of 12.80 mm and 10.23 mm for PCLR and PCLR+IB, respectively, at 134 N (P=.023). No significant differences were found in overall construct stiffness between groups. These data suggest a checkrein mechanism of action for the internal brace in this construct, rather than a load-sharing mechanism. Importantly, the PCLR+IB technique did not constrain posterior translation more than the intact, physiologic state. Clinical studies are warranted to determine whether these ex vivo biomechanical benefits will translate to improved outcomes.