A. Orsi

Failure locus of the anterior cruciate ligament: 3D finite element analysis

Anterior cruciate ligament (ACL) disruption is a common injury that is detrimental to an athletes quality of life. Determining the mechanisms that cause ACL injury is important in order to develop proper interventions. A failure locus defined as various combinations of loadings and movements, internal/external rotation of femur and valgus and varus moments at a 25o knee flexion angle leading to ACL failure was obtained. The results indicated that varus and valgus movements were more dominant to the ACL injury than femoral rotation. Also, Von Mises stress in the lateral tibial cartilage during the valgus ACL injury mechanism was 83% greater than that of the medial cartilage during the varus mechanism of ACL injury. The results of this study could be used to develop training programmes focused on the avoidance of the described combination of movements which may lead to ACL injury.

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.

The effects of graft size and insertion site location during anterior cruciate ligament reconstruction on intercondylar notch impingement

BACKGROUND Intercondylar notch impingement is detrimental to the anterior cruciate ligament (ACL). Notchplasty is a preventative remodeling procedure performed on the intercondylar notch during ACL reconstruction (ACLR). This study investigates how ACL graft geometry and both tibial and femoral insertion site location may affect ACL-intercondylar notch interactions post ACLR. A range of ACL graft sizes are reported during ACLR, from six millimeters to 11mm in diameter. Variability of three millimeters in ACL insertion site location is reported during ACLR. This study aims to determine the post-operative effects of minor variations in graft size and insertion location on intercondylar notch impingement. METHODS Several 3D finite element knee joint models were constructed using three ACL graft sizes and polar arrays of tibial and femoral insertion locations. Each model was subjected to flexion, tibial external rotation, and valgus motion. Impingement force and contact area between the ACL and intercondylar notch compared well with experimental cadaver data from literature. RESULTS A three millimeter anterior-lateral tibial insertion site shift of the maximum size ACL increased impingement force by 242.9%. A three millimeter anterior-proximal femoral insertion site shift of the maximum size ACL increased impingement by 346.2%. Simulated notchplasty of five millimeters eliminated all impingement for the simulation with the greatest impingement. For the kinematics applied, small differences in graft size and insertion site location led to large increases in impingement force and contact area. CONCLUSIONS Minor surgical variations may increase ACL impingement. The results indicate that notchplasty reduces impingement during ACLR. Notchplasty may help to improve ACLR success rates.

The Effects of Graft Size and Insertion Site Location During Anterior Cruciate Ligament Reconstruction on Intercondylar Notch Impingement

Intercondylar notch impingement is detrimental to the anterior cruciate ligament (ACL). Notchplasty is a preventative remodeling procedure performed on the intercondylar notch during ACL reconstruction (ACLR). This study investigates how ACL graft geometry and both tibial and femoral insertion site location affect ACL-intercondylar notch interactions post ACLR. A range of ACL graft sizes are reported during ACLR, from 6mm–11mm in diameter. Minor variability of up to 3mm in ACL insertion site locations is reported during ACLR. Several 3D finite element (FE) knee joint models were constructed using three ACL graft sizes and polar arrays of tibial and femoral insertion site locations. Each knee model was subjected to flexion, tibial external rotation, and valgus motion. Impingement force and contact area between the ACL and the intercondylar notch compared well with published cadaver study results. A 3mm shift in the antero-lateral direction of the tibial insertion site of the average and maximum size ACL increased impingement force by 155.4% and 242.9% respectively. A 3mm shift in the anterior-proximal direction of the femoral insertion site of the average and maximum size ACL increased impingement by 292.6%, and 346.2% respectively. Simulated notchplasties of 4mm and 5mm reduced graft impingement force by 89.4% and 100% respectively for the simulations with greatest impingement. For the kinematics applied, the results show that small differences in graft size and insertion site location may lead to large increases in impingement force and contact area. The study aims to improve ACLR success rates by understanding how minor variations in graft size and insertion site location affect intercondylar notch impingement. Because minor variations in insertion site location during ACLR are a known occurrence, the results of this study may support the argument for performing notchplasty during ACLR.Copyright

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

The Effect of Rate Dependency on the ACL Failure Locus: A Subject Specific Study

A full or partial tear of the anterior cruciate ligament (ACL) is a common and painful injury that has been estimated to occur 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

Development of a failure locus for a 3-dimensional anterior crutiate ligament: A finite element analysis

This study investigates the combinations of loading which cause injury to knee joint ligaments. A 3D model of a knee, including bones, cartilage, menisci and ligament bundles was created from magnetic resonance images (MRI). Material properties for bone, cartilage, meniscus and ligament were all determined based on previous published work. The model incorporates a novel approach for accounting for prestrain in ligament bundles. The ligament bundle structures were resized based to their zero load lengths and strained to their reference lengths at full extension using FEBio (University of Utah). Previous studies investigating ligament failure used 1D nonlinear spring elements for ligament structures. The 3D ligament model will provide improved accuracy for locating bundle ruptures. By monitoring stresses and strains in ligament bundles during knee joint orientation simulations, ruptures can be virtually diagnosed. The results of these simulations can be used in clinical applications. In sports where anterior cruciate ligament (ACL) injuries are prevalent, training programs can be adapted to address the avoidance of harmful knee orientations. The ability to monitor where bundle ruptures occur will provide increased insight for practitioners in identifying more precise mechanisms of injury to ligaments and cartilage within the knee joint.

Development of a Failure Locus for a 3-Dimensional Anterior Crutiate Ligament: A Finite Element Analysis

This study investigated movement combinations which may cause injury to the anterior cruciate ligament (ACL). A 3-Dimensional finite element knee joint model, including bones and ligament bundles, was developed. Bone was modeled as rigid, and a transversely isotropic material was applied to the ligament structures. This study incorporates a novel approach for developing bundle specific prestrain within the ligament structures. The bundles were stretched from their zero load lengths to their reference lengths, producing a strain field mimicking in vivo conditions at full knee extension. A failure locus was created by performing multiple knee joint motion combination simulations until ligament failure. The locus shows which movement combinations of internal/external femoral rotation and varus/valgus angle cause failure within the ACL bundles at 25° of knee flexion. The 3D model provided improved accuracy for locating bundle ruptures. By monitoring stresses and strains within the ligament bundles during knee joint orientation simulations, ruptures were virtually diagnosed. The relationship between knee joint orientation and ligament rupture provides a spectrum for the propensity of ACL injury. The results highlight femoral external rotation relative to the tibia as an important factor related to ACL injury. The results also show the posterolateral bundle to be more susceptible to rupture than the anteromedial bundle. These results have various clinical applications. In sports where ACL injuries are prevalent, training programs can be adapted to address the avoidance of harmful knee orientations. Monitoring bundle rupture locations also increases insight for practitioners in identifying more precise injury mechanisms.Copyright

The Development of a Three Dimensional Anterior Cruciate Ligament Failure Locus: A Finite Element Analysis

A full or partial tear of the anterior cruciate ligament (ACL) is a common and painful injury that has been estimated to occur 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