RESUMO
Over the past decades, the development of high performance lightweight polymer nanocomposites and, in particular, of epoxy nanocomposites has become one the greatest challenges in material science. The ultimate goal of epoxy nanocomposites is to extrapolate the exceptional intrinsic properties of the nanoparticles to the bulk matrix. However, in spite of the efforts, this objective is still to be attained at commercially attractive scales. Key aspects to achieve this are ultimately the full understanding of network structure, the dispersion degree of the nanoparticles, the interfacial adhesion at the phase boundaries and the control of the localization and orientation of the nanoparticles in the epoxy system. In this Personal Account, we critically discuss the state of the art and evaluate the strategies to overcome these barriers.
RESUMO
Objetivo. Estudiar la integración de una plastia tendinosa en la reparación de un ligamento cruzado anterior (LCA) y el proceso de «ligamentización» con túneles de diferente calibre. Material y métodos. Estudiamos la integración del LCA en 41 ovejas adultas, según los siguientes grupos: grupo A: plastia tendinosa autóloga del tendón flexor superficial de la pezuña en túnel femoral y tibial de 5mm de diámetro; grupo B: en túneles de 7mm de diámetro. Sacrificio a los 3, 6 y 12 meses. Efectuamos un estudio histológico de la plastia en el túnel femoral, en el túnel tibial e intraarticular. También analizamos biomecánicamente el complejo fémur-plastia-tibia, con túneles de diferente diámetro y distintos tiempos de evolución. Resultados. En los túneles de 5mm no vimos integración directa de la plastia con el hueso. Observamos un tejido fibroso celular y vascularizado. En los túneles de 7mm tampoco observamos unión directa de la plastia con el hueso. El tejido de interfaz era un tejido fibroso con una estructura fascicular desarrollando la formación de septos y penetración de vasos. Macroscópicamente la plastia seguía recordando al tendón original. Las plastias de túnel de 7mm y con mayor tiempo de evolución necesitaban más fuerza de rotura y presentaban mayor elongación que las plastias de túneles de 5mm. Conclusión. Histológicamente, al año de evolución, el tendón no se transformó en un ligamento y no había integración de la plastia con el hueso de los túneles, independientemente del diámetro de éstos (AU)
Objective. To analyse the bone-ligament integration «ligamentization» of the tendon graft in the reconstruction of anterior cruciate ligament (ACL) performing tunnels of different diameter. Material and methods. We performed the same reconstruction procedure using an autologous tendon graft taken from the superficial tendon of the hoof in 41 adult sheep. In Group A the tibial and femoral tunnels were 5mm in diameter and in Group B they were 7mm in diameter. The sheep were sacrificed at 3, 6 and 12 months after the surgery. Histological studies were performed on the graft and the tunnels, as well as a biomechanical analysis of the tibial-femoral complex. Results. In group A we did not observe direct integration of the bone and the tendon graft or any fibres joining both structures, although there was vascularized fibrous tissue. In group B we did not observe any direct binding of the bone and the tendon graft either, although there was abundant fibrous tissue. The tendon graft showed a fascicular structure that increased over time in order to create septa for vascular penetration. Macroscopically the ACL graft had a dense appearance, which was very similar to the original tendon graft. The tendon grafts from group B and with a longer follow up period required a higher strength to produce maximum breakage than the tendon grafts from group A. Conclusion. After one year follow up, the histological study shows that the tendon graft is not transformed into a ligament, and there is no integration of the tendon graft in tunnels regardless of their diameter. Therefore, fixation techniques are essential to maintain the orientation and tension of the tendon graft (AU)
Assuntos
Animais , Masculino , Feminino , Ovinos/anormalidades , Ovinos/cirurgia , Transferência Tendinosa/métodos , Transferência Tendinosa/veterinária , Ligamento Cruzado Anterior/patologia , Ligamento Cruzado Anterior/cirurgia , Reconstrução do Ligamento Cruzado Anterior/métodos , Reconstrução do Ligamento Cruzado Anterior/veterinária , Implantes Experimentais , Implantes Experimentais/veterinária , Ligamento Cruzado Anterior/fisiopatologia , Ligamento Cruzado Anterior , Reconstrução do Ligamento Cruzado AnteriorRESUMO
OBJECTIVE: To analyse the bone-ligament integration «ligamentization¼ of the tendon graft in the reconstruction of anterior cruciate ligament (ACL) performing tunnels of different diameter. MATERIAL AND METHODS: We performed the same reconstruction procedure using an autologous tendon graft taken from the superficial tendon of the hoof in 41 adult sheep. In Group A the tibial and femoral tunnels were 5 mm in diameter and in Group B they were 7 mm in diameter. The sheep were sacrificed at 3, 6 and 12 months after the surgery. Histological studies were performed on the graft and the tunnels, as well as a biomechanical analysis of the tibial-femoral complex. RESULTS: In group A we did not observe direct integration of the bone and the tendon graft or any fibres joining both structures, although there was vascularized fibrous tissue. In group B we did not observe any direct binding of the bone and the tendon graft either, although there was abundant fibrous tissue. The tendon graft showed a fascicular structure that increased over time in order to create septa for vascular penetration. Macroscopically the ACL graft had a dense appearance, which was very similar to the original tendon graft. The tendon grafts from group B and with a longer follow up period required a higher strength to produce maximum breakage than the tendon grafts from group A. CONCLUSION: After one year follow up, the histological study shows that the tendon graft is not transformed into a ligament, and there is no integration of the tendon graft in tunnels regardless of their diameter. Therefore, fixation techniques are essential to maintain the orientation and tension of the tendon graft.
