Srinath S. Chakravarthy

New algorithms for discrete dislocation modeling of fracture

The application of discrete dislocation (DD) dynamics methods to study materials with realistic yield stresses and realistic cohesive strengths requires new algorithms. Here, limitations of the standard algorithms are discussed, and then new algorithms to overcome these limitations are presented and their successes demonstrated by example. With these new methods, the stability, accuracy and robustness of the DD methodology for the study of deformation and fracture is significantly improved.

The effects of knee joint kinematics on anterior cruciate ligament injury and articular cartilage damage

This study determined which knee joint motions lead to anterior cruciate ligament (ACL) rupture with the knee at 25° of flexion. The knee was subjected to internal and external rotations, as well as varus and valgus motions. A failure locus representing the relationship between these motions and ACL rupture was established using finite element simulations. This study also considered possible concomitant injuries to the tibial articular cartilage prior to ACL injury. The posterolateral bundle of the ACL demonstrated higher rupture susceptibility than the anteromedial bundle. The average varus angular displacement required for ACL failure was 46.6% lower compared to the average valgus angular displacement. Femoral external rotation decreased the frontal plane angle required for ACL failure by 27.5% compared to internal rotation. Tibial articular cartilage damage initiated prior to ACL failure in all valgus simulations. The results from this investigation agreed well with other experimental and analytical investigations. This study provides a greater understanding of the various knee joint motion combinations leading to ACL injury and articular cartilage damage.

Investigating the effects of knee joint motion schemes on knee joint injury: A finite element analysis

This study uses a three dimensional model of the knee joint to determine which knee joint motion schemes lead to ACL injury, while exploring the possible types of concomitant injuries associated with each motion scheme. The physical elements of the knee joint including bones, articular cartilage, meniscus and ligaments were obtained by reconstructing magnetic resonance images. A failure locus representing the relationship between motion schemes and knee joint injury was created from finite element simulations considering knee flexion, femoral axial rotation and both valgus and varus motion. The relationships between knee joint orientation and various tissue failures were examined and susceptibility spectrums for knee injuries were obtained. The posterolateral bundle demonstrated higher rupture susceptibility than the anteromedial bundle. The average varus angular displacement for ACL failure was 46.6\% lower than the average valgus angular displacement. Femoral external rotation decreases overall ACL valgus/varus failure angle by 27.5\% compared to internal rotation. Articular cartilage injury was shown to occur prior to ACL failure in all valgus simulations. A simplified and computationally efficient version of the full 3D model showed close correlation to the complete model with respect to ligament failure and shows that if only ligament failure is of interest, a simple model can be used. The results of this study highlight several detrimental joint motions and can aid in improved clinical diagnoses and improved training programs for athletes.

Uncovering the Mechanism of Soft Tissue Injuries Associated With ACL Tear

Anterior cruciate ligament (ACL) injury is a common and painful injury that occurs approximately 250,000 times annually in the U.S. [1]. Articular cartilage and meniscal injuries are also associated with ACL injuries [2]. ACL injuries can often lead to degenerative osteoarthritis of the articular cartilage [2]. An epidemiology study of athletic injuries by Majewski et al. [3] determined that out of 19,530 sports injuries, 20% were ACL injuries and 8% were medial collateral ligament (MCL) injuries.Copyright