Optimizing tunnel placement for lateral extra-articular procedures in pediatric epiphyseal anterior cruciate ligament reconstruction: a three-dimensional simulation study of physeal damage and safe zone identification

INTRODUCTION: Lateral extra-articular procedures (LEAP) are increasingly used in anterior cruciate ligament (ACL) reconstruction (ACLR) in patients with open growth plates, reducing graft failure in high-risk populations. This study aimed to determine safe tunnel orientations for epiphyseal ACLR, identify the anterolateral ligament (ALL) position relative to the physis, quantify physeal damage, and define safe zones for LEAP to prevent physeal injury and tunnel collision using three-dimensional (3D) simulation. METHODS: Magnetic resonance images of patients aged 10-17 were analyzed to create 3D models of the distal femur and distal femoral physis (DFP). ACL tunnels were simulated with 8-mm drills from the ACL-femoral insertion in anterolateral (AL) and direct lateral (DL) directions while avoiding lateral structures, the physis, and articular surface. ALL drillings used 4-mm drills with 20-mm depth from the ALL-femoral insertion across a 70° cone. Safe zones were defined as directions where neither the DFP nor ACL tunnel were breached. Physeal injury was quantified as a percentage of total physeal volume. STATISTICAL ANALYSES: Student's t-test, one-way ANOVA, and simple linear regression (p<0.05). RESULTS: ) and greater drilling length (34 vs 26 mm) than the DL direction. ALL footprints were located between the DFP borders in 58% of cases, with a median distance of 1.74 mm IQR 2.13 to the DFP center, decreasing with age (p<0.05). Maximum DFP damage with LEAP occurred with horizontal drilling (10°-cephalic, 5°-posterior), resulting in 1.67% SD 0.78 physeal injury. Optimal safe zone directions for LEAP were 21° distal and 18° anterior for DL approaches and 18° distal and 17° posterior for AL approaches, with AL approaches providing a larger angular area (p<0.05). No other significant differences by age or sex were observed. CONCLUSIONS: This 3D-simulation quantifies physeal damage, establishes safe zones for epiphyseal ACLR, and defines optimal LEAP drilling and fixation orientations. The AL approach provides a wider safe zone and greater drilling length for the epiphyseal ACL tunnel, with the potential to minimize the risk of physeal injury and tunnel collisions during LEAP drilling or fixation. STUDY DESIGN AND LEVEL OF EVIDENCE: Descriptive Laboratory Study; Level V.