Biomechanical Evaluation of the Transtibial Pull-Out Technique for Posterior Medial Meniscal Root Repairs Using 1 and 2 Transtibial Bone Tunnels

Background: Current methods of the transtibial pull-out meniscal root repair significantly displace under cyclic loading in porcine models but have not been evaluated in human models. One potential explanation for the displacement is that a single transtibial tunnel may not fully restore the attachment of the entire posterior medial meniscal root. Purpose/Hypothesis: The purpose of this study was to biomechanically evaluate the transtibial pull-out technique in a human cadaveric model using either 1 or 2 transtibial bone tunnels. The hypothesis was that a transtibial pull-out technique using 2 transtibial bone tunnels would confer superior biomechanical properties in comparison to an iteration using 1 transtibial bone tunnel. Study Design: Controlled laboratory study. Methods: Ten matched pairs of male human cadaveric knees (average age, 52.7 years) were randomly assigned (1 each of the pair) to 2 groups consisting of a transtibial pull-out technique using either 1 or 2 transtibial bone tunnels. The knees were cyclically loaded for 1000 cycles from 10 to 30 N at 0.5 Hz, representing the loads experienced during a typical meniscal root repair postoperative rehabilitation program, and then pulled to failure at a rate of 0.5 mm/s. Results: Differences between 1- and 2-tunnel repair groups were neither statistically nor clinically significant with respect to displacement or ultimate failure load. On average, the 1- and 2-tunnel repair groups resulted in 3.32 mm and 3.23 mm of displacement, respectively, after 1000 testing cycles. At 1, 100, 500, and 1000 testing cycles, displacement was not significantly different between groups ( P > .799). The 2-tunnel repair technique resulted in a 10.2% higher ultimate failure load (135 N vs 123 N); however, this was not significant ( P = .333). Conclusions: Similar biomechanical properties were seen between transtibial pull-out repairs using either 1 or 2 transtibial bone tunnels in a human cadaveric model. Both repair groups exceeded the 3-mm threshold for nonanatomic displacement. Clinical Relevance: This study indicates that a newly proposed iteration of the transtibial pull-out repair technique using a second transtibial tunnel, which theoretically restores more of the posterior medial meniscal root, was almost identical to the current clinical standard involving a single transtibial tunnel. As the importance of repairing meniscal root tears is increasingly recognized, further studies on new iterations of both techniques are warranted to minimize the risk of displacement caused by early motion in the initial postoperative rehabilitation period.