A new device to measure the structural properties of the femuranterior cruciate ligament-tibia complex

Previous studies of biomechanical properties of femur-anterior cruciate ligamenttibia complex (FATC) utilized a wide variety of testing methodologies Introduction The anterior cruciate ligament (ACL) has a very complex anatomy which enables it to perform an important role in guiding knee motion. As the knee undergoes flexionextension, internal-external, and varus-valgus rotation, the length and orientation of the ACL change significantly. The broad attachments of the ACL to both the femur and the tibia allow various portions of the ligament to be relatively taut throughout a full range of knee motion. So, given a particular orientation of the knee, some collagen bundles of the ACL experience tension while other bundles are unloaded Previous studies of the biomechanical properties of the femur-ACL-tibia complexes (FATC) utilized knee orientations and loading directions which were poorly documented and seemingly arbitrary with respect to the ligament orientation relative to the direction of applied load. Thus, data are difficult to compare with one another. Viidik [5] investigated the structural properties of the FATC in rabbits with the knee in a fully extended position and with the femur, tibia, and ACL all aligned along the axis of the applied tensile load. Gupta et al. [6] used a similar experimental set up to test the FATC of canines, but with the tibia externally rotated 90 deg relative to the femur to eliminate the natural twist in the ACL. Noyes and Groo

Biomechanics and anterior cruciate ligament reconstruction

For years, bioengineers and orthopaedic surgeons have applied the principles of mechanics to gain valuable information about the complex function of the anterior cruciate ligament (ACL). The results of these investigations have provided scientific data for surgeons to improve methods of ACL reconstruction and postoperative rehabilitation. This review paper will present specific examples of how the field of biomechanics has impacted the evolution of ACL research. The anatomy and biomechanics of the ACL as well as the discovery of new tools in ACL-related biomechanical study are first introduced. Some important factors affecting the surgical outcome of ACL reconstruction, including graft selection, tunnel placement, initial graft tension, graft fixation, graft tunnel motion and healing, are then discussed. The scientific basis for the new surgical procedure, i.e., anatomic double bundle ACL reconstruction, designed to regain rotatory stability of the knee, is presented. To conclude, the future role of biomechanics in gaining valuable in-vivo data that can further advance the understanding of the ACL and ACL graft function in order to improve the patient outcome following ACL reconstruction is suggested

Evaluation of Knee Stability with Use of a Robotic System

In our research center, we have developed and utilized a novel robotic/universal force-moment sensor testing system to gain quantitative data on multiple-degree-of-freedom kinematics of the knee simultaneously with data on the in situ forces in normal and repaired soft tissues. In particular, we have investigated the complex interaction of the anteromedial and posterolateral bundles of the anterior cruciate ligament as well as several key biomechanical variables in anterior cruciate ligament reconstruction, such as graft selection and femoral tunnel placement (both of which impact knee stability). For example, both the bone-patellar tendon-bone and quadrupled hamstrings tendon autografts restored anterior stability but were insufficient in gaining rotatory stability. In a follow-up study, we have shown that a more laterally placed graft was beneficial and could improve these outcomes. Such findings led to additional investigation in which the biomechanical advantages of double-bundle anterior cruciate ligament reconstruction were demonstrated. However, a more laterally placed autograft at the femoral insertion of the posterolateral bundle also worked well, especially when the knee was nearly at full extension (a position in which the anterior cruciate ligament is needed most). At present, we are moving forward by obtaining in vivo kinematics data and then repeating those kinematics exactly to obtain new data with use of the robotic/universal force-moment sensor testing system in order to gain further insight regarding the function of the anterior cruciate ligament and anterior cruciate ligament replacement grafts in vivo. In parallel, we are developing a mathematical model of the knee and validating the computational model with experimental data. The combined approach will yield new and relevant information, including the stress and strain distribution in the anterior cruciate ligament and anterior cruciate ligament grafts. This will facilitate a better understanding of the function of the anterior cruciate ligament and a scientifically based design of surgical procedures and postoperative rehabilitation protocols that will lead to better patient outcomes