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Anterior cruciate ligament injuries commonly in traffic accident, sports activities and extreme sports. Anterior cruciate ligament reconstruction is a common practice to help the patients restore the knee stability. However, there is no previous comparison study of single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction with respect to biomechanical characteristics such as rotational stability, force and stress inside the ligament and grafts, stresses inside the soft tissues. In this study, we developed a pair of three-dimensional finite element models of a lower extremity including femur, tibia, fibula, cartilage, meniscus, and four major ligaments at 0°，25°，60° and 80°of knee flexion. Based on the intact models, single bundle reconstruction, double-femoral double-tibial tunnel reconstruction, single-femoral double-tibial tunnel reconstruction, and double-femoral single-tibial tunnel reconstruction models were also developed. Then, the anterior tibial translations, the forces and stresses inside the ACL and ACL replacements, as well as the stresses inside the menisci, femoral and tibial cartilage were predicted under a combined rotatory load of 10Nm valgus moment and 5 Nm internal torque, respectively using finite element analysis. The rotational stability, ligament forces and stresses in the menisci, femoral and tibial cartilage following double bundle augmentation were superior to the other reconstruction techniques, while there is little advantage in ligament stress compared to that of the single bundle reconstruction. We conclude that double-femoral double-tibial tunnel reconstruction may have advantages with regard to biomechanical characteristics such as rotational stability, force inside the ligament and grafts, stresses inside the soft tissues.

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Signcryption is a public key cryptosystem that achieves the functions of digital signature and public key encryption simultaneously. It significantly reduces the cost of traditional signature‐then‐encryption approach. Although a large body of signcryption schemes have been proposed, few works have been done on attribute‐based signcryption (ABSC), which simultaneously achieves the functionalities of attribute‐based encryption and attribute‐based signature, two important cryptographic primitives proposed to enforce fine‐grained access control and user authentication in cloud computing applications. In this paper, we present a threshold ABSC scheme. The scheme is proven secure under the well‐established Decisional Bilinear Diffie–Hellman and the standard Computational Diffie–Hellman assumptions in the standard model. Compared with the state of the ABSC art, our scheme has comparable efficiency without relying on any random oracle. Furthermore, we construct an authenticated key agreement protocol based on this threshold attribute‐based signcryption from the point of improving the security of cloud computing. Copyright © 2016 John Wiley & Sons, Ltd.