Poster 351: Relation Between Femoral Anterior Cruciate Ligament Tunnel Orientation and Anterolateral Ligament Tunnel Collision in a 3D-CT Model

Objectives: The anterolateral ligament (ALL) is an important structure for knee stability and has roles in maintaining internal rotation anterior-posterior anterior cruciate (ACL)- insufficient knees. There a growing body of evidence demonstrating superior clinical outcomes including reduced graft failure rate residual pivot shift with combined ACL ALL reconstruction compared to isolated reconstruction. One common complication this procedure convergence the two tunnels used passage. Several studies have aimed determine optimal angles drill these that minimizes collision risk, but most literature limited by few angle combinations or manipulation tunnel exclusively. study examined how changing orientation femoral affected they their investigation relation line perpendicular axis. We aim investigate between coronal axial planes risk as measured minimum distance (MDBT). hypothesize there correlation both planes. Methods: This was determined be non-human subjects research Institutional Review Board. A 3D-CT anatomically normal radiologist de- identified exported into 3D modeling software Autodesk Fusion 360. model prepared analysis based on previous knee. central longitudinal axis femur set long axis, rotated so trans-epicondylar oriented x-axis. then parallel z-axis sagittal plane. Based results multiple prior evaluating orientation, “safe” 40° plane 10° proximal all ALL-ACL combinations. attachment site designated 8mm 4.3mm posterior lateral epicondyle. modeled cylinder 30mm 6mm diameter center placed at site. 4mm one end represent EndoButton tunnel. cylinders were 15° increments up 60° until 25 unique orientations created. (Figure 2) For each large face anatomic footprint, extended Endobutton penetrated cortex. MDBT measured, 2mm clearance satisfactory avoid convergence. recorded if overlapped model. Linear regression dependent variable independent variables angles. Significance p < 0.05. Results: occurred 36% orientations, unsatisfactory 20% remaining 44%. producing largest average 0°, 9.47mm zero collisions across also 3.93mm An produced lowest 1.26mm three collisions. linear had R 2 0.424. negative association indicating increases, decreases (β = –0.654 ,p 0.001). no =0.209, p=0.19). Conclusions: Despite using avoiding collisions, dangerously close proximity over half tested. These findings help reinforce ACL- high not properly accounted for. They raise awareness even when deemed remains proportion create demonstrates held constant, more anteriorly angled increases collision. Further work should involve performing similar methodology larger scale patients, order population. suggest role preoperative planning individual level, given differences patients. [Table: see text]