Comparison of the split stacked versus the split Achilles allograft for dual femoral tunnel posterior cruciate ligament reconstruction

Background: Cadaveric testing has shown that double-bundle reconstruction better replicates the native anatomy of the posterior cruciate ligament. With the current trend toward allograft Achilles posterior cruciate ligament reconstructions, the need to determine a graft configuration with the highest tensile and pull-out strength has become paramount. Hypothesis: The split stacked Achilles allograft construct provides greater graft material to traverse the notch and provides increased load to failure at the tibial point of fixation compared with a standard monoblock Achilles allograft construct. Study Design: Controlled laboratory study. Methods: Eight matched pairs of Achilles allograft tendons were secured to 8 matched pairs of fresh-frozen human cadaveric tibiae. Group 1 consisted of single-block grafts (n = 8), and group 2 included the split stacked grafts (n = 8). The cross-sectional area of each graft's 2 collagenous bundles was measured with a micrometer. The graft constructs were pulled to ultimate failure at a rate of 50 mm/min on a materials testing machine. Results: The mean cross-sectional area of the group 2 split stacked grafts (76.6 ± 3.1 mm²) was significantly greater than that of the group 1 single-block grafts (48.2 ± 3.0 mm²; P =.00006). The maximum load to failure of the group 2 construct was significantly greater (1383 ± 102 N) than that of the group 1 single-block configuration (1020 ± 136 N; P =.01). Conclusion: These results indicate that the novel split stacked configuration of an Achilles tendon allograft provides a greater cross-sectional area of graft material across the joint as well as a significant increase in the overall load to failure strength compared with a standard monoblock Achilles allograft construct. Clinical Relevance: The split stacked Achilles graft is an efficient method for using the entire allograft. With maintenance and use of all collagen fibers, the split stacked Achilles construct provides essentially 2 grafts in 1 while only using a single tibial tunnel.