| Background:In recent years, the incidence of anterior cruciate ligament(ACL) injury gradually increased. It has reached a consensus that the ACL, which plays an important role in stabilizing the knee joint, should be reconstructed if it was severely torn. At present, autohamstring tendon graft was the most preferred graft selection for reconstructing ACL. As the hamstring tendons are long and thin, they are often folded into 4 strands to acquire appropriate length, diameter and biomechanical property, which were the most important premise for gaining excellent result after ligament reconstruction operation. But, the relevant research about how to maintain multi-strand tendons sutured in iso-tension status is rare now.Objective:1. To design a new tendon tensioning platform, which could help surgeon suture multi-strand tendons in iso-tension status.2. Suturing tendons in different tension and analysising the effect of iso-tension or non-i so tension on biomechanical property of tendon grafts.Methods:First part:To design a new tendon tensioning platform.Designing Principle: This new platform should contain two independent pulling module. each module could stretch a single tendon independently,and suturing could be accomplished during the pretension process. The platform should be handled conveniently and can tolerate high temperature and high air pressure.Second part:Experiment about the effect of suturing with iso-tension or non-isotension on the biomechanical property of tendon grafts.60 tendons were divided into 3 groups, each group had 20 tendons and every two tendons were sutured into one tendon graft. The group I was the 4-strand iso-tension group, in which the 4 strands tendon were all pulled at a force of 20N in the suturing process. The group II was the 3-strand iso-tension group, in which 3 strands tendon were pulled at a force of 20N, and the other one was not exerted any force in the suturing process. The group III was the 2-strand iso-tension group, in which 2 strands tendon were pulled at a force of 20N, and the other two were not exerted any force. Measuring the diameter of all tendon grafts and calculating their average cross section area. Then the mechanical test was undertaken to evaluate the biomechanical effect of suturing with iso-tension or non-isotension.Results:First part:We developed a new multi-strand tendon tensioning platform, which consist of two tendon traction modules. It can stretch 4 strands tendon simultaneously, and make it possible to perform suturing during the tendon traction process. This new platform can show the tension level and make it possible to implement the traction with every strand tendon in the same tension. This platform is made of stainless steel and Polytetrafluoroethylene, which can be sterilized with high temperature and pressure.Second part:The average cross section area and length of tendon graft in 3 group have no statistical difference (p>0.05). The graft stiffness in I group is (150.66±42.15)N/mm, which is larger than that of group II and III(p<0.01);.The graft normalizing stiffness in I group is (213.22±72.23) MPa, which is also larger than that of group II and III (p<0.05). There is a turning point in the load-displacement curve of non-isotension group. The stiffness and normalizing stiffness befor and post-point have statistical differences. All the failure occurred at the fixation site, and we didn't observe any tendon rupture.Conclusions:1. The new platform that we designed and developed to help suture multi-strand tendons at identical tension level is a practical instrument for the graft preconditioning.2. The tension of all strands tendon should be kept at an identical level during the suturing process, so as to ensure that the grafts have the most stable biomechanical properties.
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