Design and optimization of the graft pretension protocol for the reconstruction of the anterior cruciate ligament (ACL)

Anterior cruciate ligament (ACL) rupture is one of the mayor concerns of today’s professional high demand athletes due to its high probabilities of happening and slow recovery. In general, the grafts used in ACL reconstruction surgeries are tendons taken from the same patient in order to reduce the possibility of rejection. However, these soft tissue grafts share viscoelastic properties which produce an elongation of the graft after its implantation, which if too much can lead to an invalid surgery. Thus, in order to eliminate this undesired property, the tendon needs to be preconditioned after its removal from the patient and before the re-implantation. This procedure involves a graft board to be able to apply a specific load to the tendon, thus being able to elongate it before its final implantation in the affected person. However, this protocol has not been standardized to date, hence each surgeon proceeds in their own way. The main goal of this project is to design and optimize a graft pretension protocol for the reconstruction of the anterior cruciate ligament. Digital Extensor Bovine tendons were used in order to test the quality and efficiency of the proposed protocols. Using a hydraulic machine, an ACL reconstruction surgery was simulated. A successful surgical procedure is determined by the graft elongation after its implantation in the knee, which if elongated too much invalids the reconstruction, not being able to achieve the natural ACL functions. Thus, out of all the parameters obtained, the most important one and so, taken into account for the discussion, is the elongation of the graft in the rehabilitation process. Using this parameter, protocols can be compared. Two out of the three protocols proposed show to be statistical different from the control group. The third one produced a high elongation of the tendon grafts due to the small value load applied to them. As no significant difference was found between the two successful protocols, we can determine that the one implying less load would be the best one for its reproducibility in the operating room. In conclusion, a pretension protocol is beneficial to the grafts as it reduces post-surgery elongation and it has to consist of at least 89 N in order to be able to eliminate part of the graft’s intrinsic viscoelastic properties.Ingeniería Biomédica (Plan 2010