Biomechanical Comparisons of Bone-Patellar Tendon-Bone Graft With or Without Suture Tape for Anterior Cruciate Ligament Reconstruction

Author(s): Hong Li, Lawrence Berglund, Subin Lin, Zhanwen Wang, Aaron J. Krych, Chunfeng Zhao

The suspensory fixations are utilized as femoral fixation for BPTB grafts with the advantages of precise position of the tunnel and high tensile strength. However, there remains a concern that BPTB grafts fixed with sutures and button might fail as a result of bone plug fracture or sutures cutting through the bone. The aim of this study was to investigate the biomechanical strength of bone-patellar tendon-bone (BPTB) graft with or without independent suture tape reinforcement in anterior cruciate ligament (ACL) reconstruction. Twenty-four knees from dogs were used, including ACL-intact knees (Intact group, n = 8), ACL reconstructed knees (BPTB group, n = 8), and ACL reconstructed knees with suture tape augmentation (BPTB- internal brace (IB) group, n = 8). Specimens were mounted on the MTS system by securing the femur and tibia within custom-made clamps. The joint was positioned in 30° of flexion. A 67 N anterior tibial loading condition was applied to test anterior tibial translation (ATT, mm). After loading, the devices and construct grafts were further displaced at 50 mm/min until failure. The failure mechanism was recorded. Cyclic displacement at 67 N (mm), ultimate failure load (N), and pullout stiffness (N/mm) were determined. Under the 67 N anterior tibial load, the ATT was 1.3 ± 0.3 mm for the intact group, 8.0 ± 5.0 mm for the BPTB group, 2.1 ± 1.0 mm for the BPTB-IB group. The ATT of the BPTB-IB group was significantly lower than that of the BPTB group (p < 0.001).

Regarding the failure mode during the failure testing, the BPTB group had all samples of sutures cutting through the bone and the BPTB-IB group failed in all samples by breakage or loosening of suture tape and then sutures cutting through the bone. The BPTB-IB group had a higher ultimate failure load than the BPTB group (668 ± 159 N vs 230 ± 87 N; p < 0.001). The mean stiffness of the BPTB-IB group was also significantly higher than that of the BPTB group (28 ±7 N/mm vs. 11 ± 3 N/mm; p < 0.001). The suture tape augmentation increased knee stability and ACL failure strength after ACL reconstruction with BPTB. Therefore, this technology could be helpful to reduce the complications of ACL reconstruction such as graft failure and promote patients back activities sooner after reconstruction, especially for the young athletic patients.

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