Stacked Biocomposite Screws in a Single-Stage Revision Anterior Cruciate Ligament Reconstruction Has Acceptable Fixation Strength in a Porcine Cadaveric Model

Background: Stacked screws is a commonly used technique in single-stage revision anterior cruciate ligament (ACL) reconstruction in the setting of bone loss, but there are limited data to support its use. Hypothesis: Two configurations of a biocomposite stacked screws construct have similar fixation strength and linear stiffness as a primary ACL reconstruction construct in a biomechanical model. Study Design: Controlled laboratory study. Methods: A total of 30 porcine legs were divided into 3 groups. Group 1 underwent primary ACL reconstruction with a patellar tendon graft fixed into the femur, with an 8-mm biocomposite interference screw of beta-tricalcium phosphate and poly lactide-co-glycolide. For a revision ACL reconstruction model, groups 2 and 3 had bone tunnels created and subsequently filled with 12-mm biocomposite screws. New bone tunnels were drilled through the filler screw and the surrounding bone, and the patellar bone plug was inserted. Group 2 was fixed with 8-mm biocomposite screws on the side of the graft opposite the filler screw, while group 3 had the interference screw interposed between the graft and the filler screw. The construct was loaded at 1.5 mm/s in line with the tunnel until failure. Load to failure, linear stiffness, and mode of failure were recorded. Results: The mean pullout strength for groups 1, 2, and 3 was 626 +/- 145 N, 653 +/- 152 N, and 720 +/- 125 N, respectively (P = .328). The mean linear stiffness of the construct in groups 1, 2, and 3 was 71.4 +/- 9.9 N/mm, 84.1 +/- 11.1 N/mm, and 82.0 +/- 10.8 N/mm, respectively. Group 2 was significantly stiffer than group 1 (P = .037). Conclusion: Two configurations of a biocomposite stacked screws construct for a single-stage revision ACL reconstruction in the setting of bone loss show a similar fixation strength and linear stiffness to a primary ACL reconstruction at time zero in a porcine model.

Automated summary

The study showed that two configurations of a biocomposite stacked screws construct for single-stage revision ACL reconstruction in the setting of bone loss have similar fixation strength and linear stiffness to a primary ACL reconstruction at time zero in a porcine model.