3D assessment of graft malposition after ACL reconstruction: Comparison of native and 11o'clock ligament orientations.

BACKGROUND: Femoral tunnel malposition makes up the majority of technical failures for ACL reconstructive surgery. The goal of this study was to develop adolescent knee models that accurately predict anterior tibial translation when undergoing a Lachman and pivot shift test with the ACL in the 11o'clock femoral malposition (Level of Evidence: IV). METHODS: FEBio was used to build 22 subject-specific tibiofemoral joint finite element representations. To simulate the two clinical tests, the models were subject to loading and boundary conditions established in the literature. Clinical, historical control data were used to validate the predicted anterior tibial translations. RESULTS: A 95% confidence interval showed that with the ACL in the 11o'clock malposition, the simulated Lachman and pivot shift tests produced anterior tibial translations that were not statistically different from the in vivo data. The 11o'clock finite element knee models resulted in greater anterior displacement than those with the native (approximately 10o'clock) ACL position. The difference in anterior tibial translation between the native and 11o'clock ACL orientations was statistically significant. CONCLUSION: Clinically, by understanding the impact that ACL orientation has in anterior tibial displacement biomechanics, surgical interventions can be improved to prevent technical errors from occurring. The integration of this methodology into surgical practice not only allows for anatomical visualization prior to surgery, but also creates the opportunity to optimize graft placement, thus improving post-surgical outcomes.

Comparison of side-cutting maneuvers versus low impact baseball swing on knee ligament loading in adolescent populations.

BACKGROUND: High impact sports are associated with an increased incidence rate for knee ligament injuries, specifically pertaining to the anterior cruciate ligament and medial collateral ligament. What is less clear is (i) the extent to which high impact activities preferentially load the anterior cruciate ligament versus the medial collateral ligament, and (ii) whether both ligaments experience similar stretch ratios during high loading scenarios. Therefore, the goal of this project was to assess how different loading conditions experienced through more at-risk sporting maneuvers influence the relative displacements of the anterior cruciate ligament and medial collateral ligament. The focus of the study was on adolescent patients - a group that has largely been overlooked when studying knee ligament biomechanics. METHODS: Through kinetic knee data obtained through motion capture experimentation, two different loading conditions (high vs low impact) were applied to 22 specimen-specific adolescent finite element knee models to investigate the biomechanical impact various sporting maneuvers place on the knee ligaments. FINDINGS: The high impact side cutting maneuver resulted in 102% and 47% increases in ligament displacement compared to the low impact baseball swing (p < 0.05) for both the anterior cruciate ligament and medial collateral ligament. INTERPRETATION: Quantifying biomechanical risks that sporting activities place on adolescent subjects provides physicians with insight into knee ligament vulnerability. More specifically, knowing the risks that various sports place on ligaments helps guide the selection of sports for at-risk patients (especially those who have undergone knee ligament surgery).

Pivot shift and Lachman test simulation-based exploration in juvenile populations for accurately predicting anterior tibial translation.

Advancements in technology and finite element software have made it possible to develop simulation-based exploration of subject-specific tibiofemoral joint kinematics. In this study, the goal was to develop baseline knee models that accurately predict anterior tibial displacement when undergoing a Lachman and pivot shift test. A total of 22 subject-specific adolescent tibiofemoral joint finite element representations were developed using FEBio. The models were subject to loading conditions established in the literature to simulate the two clinical tests. Anterior tibial translations that were measured through clinical, historical controls were used to validate the proposed models. A 95% confidence interval showed that the simulated Lachman and pivot shift tests of the juvenile knee models were not statistically different from the historical controls and were in accordance with the anterior tibial translations that were measured experimentally. Clinically, simulations are important in advancing the field of knee finite element modeling, particularly in pediatric applications where the surgeon must balance restoring full function in a patient who is skeletally immature and where the growth plate is vulnerable. The methodologies created in developing these foundational models can be utilized to build more anatomically complex finite element representations that can both predict ligament stresses in response to dynamic activities and analyze the effects of different insertion sites.