Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005."June 2005."Includes bibliographical references (leaves 199-216).Very little is known regarding the function of the posterior cruciate ligament in response to physiological loading conditions. A limited understanding of posterior cruciate ligament function might contribute to the poor clinical outcomes that are observed after reconstruction. Therefore, the objectives of this thesis were to quantify the biomechanical function of the posterior cruciate ligament both in-vitro and in-vivo and to investigate the effects of injury and reconstruction of the posterior cruciate ligament on knee joint biomechanics. First, muscle loading conditions were simulated in cadavers to measure the effects of posterior cruciate ligament injury and reconstruction on knee joint kinematics and contact pressures. Next, the structural properties of the grafts used in posterior cruciate ligament reconstructions were optimized using a theoretical model. In order to verify these results using an experimental model, an imaging system was developed to measure the strain distributions around the graft surface during tensile testing. Finally, the deformation of the posterior cruciate ligament was studied in living subjects using imaging and solid modeling techniques. Three-dimensional models of the knee joint, including the insertion sites of the posterior cruciate ligament were created from magnetic resonance images. The subjects then flexed their knees as they were imaged using fluoroscopy from two orthogonal directions. The models and orthogonal images were imported into a solid modeling software and used to reproduce the kinematics of the knee as a function of flexion. From these models, the three- dimensional deformation of the posterior cruciate ligament insertion sites was measured.(cont.) These data illustrated that the in-vivo function of the posterior cruciate ligament is different from that observed in in-vitro studies. Current surgical treatments of posterior cruciate ligament injuries do not account for the in-vivo function observed in this study. In summary, this thesis quantified the biomechanical role of the posterior cruciate ligament in response to physiological loading conditions. In addition, grafts used to reconstruct the posterior cruciate ligament were optimized. These data provide valuable information for developing surgical treatments that recreate the in-vivo biomechanics of the posterior cruciate ligament.Sc.D
