Optimizing Drilling Orientation for the ALL Femoral Tunnel During Anterolateral Augmentation Procedures For Minimizing Collision With the ACL Tunnel Created Using Modified Transtibial Technique

Abstract

Background: Research on surgical strategies to minimize tunnel collisions in combined anterior cruciate ligament (ACL) reconstruction (ACLR) using the modified transtibial technique (MTT) and anterolateral augmentation is limited, unlike with independent tunnel drilling techniques.Purpose: To analyze the optimal drill orientations for the anterolateral ligament (ALL) femoral tunnel to minimize tunnel collisions and reduce damage to surrounding structures during combined ACLR with MTT and anterolateral augmentation procedures, accounting for far-cortex drilling (FCD) of the ALL femoral tunnel required for graft fixation.Study Design: Descriptive laboratory study.Methods: Three-dimensional reconstructed femoral models of patients who underwent ACLR with MTT between 2015 and 2018 were used. Geometric factors of femoral models were analyzed, and virtual ALL femoral tunnels were simulated to evaluate 45 drilling combinations. To assess potential damage to surrounding structures associated with ALL femoral tunnel drilling, femoral cortical violation caused by the ALL femoral tunnel itself was assessed under each drilling condition, whereas tunnel trajectories were analyzed to classify drilling conditions according to FCD. In addition, the minimum distance between the ACL and ALL femoral tunnels (MDBT) and the tunnel collision rate were evaluated.Results: A total of 27 patients were analyzed. In scenarios where FCD was not required for ALL graft femoral fixation, the optimal drill orientation for the ALL femoral tunnel was within the range of coronal -40 degrees to -20 degrees, eliminating cortex violation and tunnel collisions (mean MDBT, 9 +/- 4.1 mm; collision rate 0%). When FCD was required for ALL graft femoral fixation, the optimal drill orientation was axial 40 degrees and coronal 10 degrees, resulting in the longest MDBT without the risk of femoral cortex violation (MDBT, 4.9 +/- 3.5 mm; collision rate, 7.4%).Conclusion: During the combined surgeries for ACLR using MTT and anterolateral augmentation procedures, the optimal drill orientation of the ALL femoral tunnel was within the range of coronal -40 degrees to -20 degrees for techniques not requiring FCD and axial 40 degrees and coronal 10 degrees for those requiring FCD.Clinical Relevance: This study provides practical surgical guidance for optimizing ALL femoral tunnel orientation during combined ACLR using MTT and anterolateral augmentation. By accounting for whether FCD is required for ALL graft femoral fixation, the findings may help surgeons minimize tunnel collision and reduce the risk of femoral cortical violation, thereby potentially decreasing procedure-related complications.