Tibial Tunnel Positioning Technique Using Bony/Anatomical Landmarks in Anatomical Anterior Cruciate Ligament Reconstruction  Hiroki Shimodaira, M.D., Keiji Tensho, M.D., Ph.D., Yusuke Akaoka, M.D., Seiji Takanashi, M.D., Ph.D., Hiroyuki Kato, M.D., Ph.D., Naoto Saito, M.D., Ph.D.  Arthroscopy Techniques  Volume 6, Issue 1, Pages e49-e55 (February 2017) DOI: 10.1016/j.eats.2016.09.003 Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 1 (A) Axial 3-dimensional computed tomography image of the left knee tibial plateau. (B) Two-tunnel arrangement for double-bundle reconstruction. Anteromedial (AM) and posterolateral (PL) bone tunnels reference the L-shaped ridge and the midpoint between the anterior border of the medial and lateral intercondylar tubercle, respectively. (C) AM tunnel placement within the anterior cruciate ligament (ACL) tibial footprint for single-bundle reconstruction: the L-shaped ridge is referenced identically to AM bundle tunnel placement. (D) Central tunnel placement: midpoint between the corner of the L-shaped ridge and the lateral intercondylar tubercle is the target point for the center of footprint. There is a risk of damage to the attachment site of the anterior horn of the lateral meniscus when creating a large bone tunnel at the center. Blue area: ACL tibial footprint; blue circle: AM bundle tunnel; yellow circle: PL bundle tunnel; red circle: single-bundle tunnel; red dotted line: Parsons' knob; green dotted line: medial intercondylar ridge (a), medial intercondylar tubercle (b), lateral intercondylar tubercle (c); white dotted line: anterior horn of lateral meniscus; blue dotted line: anterior edge of the medial and lateral intercondylar tubercle; arrowheads: Parsons' knob and medial intercondylar ridge are joined at their anteromedial edge to form the L-shaped ridge. Arthroscopy Techniques 2017 6, e49-e55DOI: (10.1016/j.eats.2016.09.003) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 2 After remnant removal, an arthroscopic bird's eye view from the anterolateral portal clearly shows the anterior cruciate ligament (ACL) tibial footprint of the right knee and surrounding bony and/or anatomical landmark. Blue area: ACL tibial footprint; red dotted line: Parsons' knob; green dotted line: medial intercondylar ridge (a), medial intercondylar tubercle (b), lateral intercondylar tubercle (c); white dotted line: anterior horn of lateral meniscus; blue dotted line: anterior edge of the medial and lateral intercondylar tubercle; arrowheads: Parsons' knob and medial intercondylar ridge are joined at their anteromedial edge to form the L-shaped ridge. Arthroscopy Techniques 2017 6, e49-e55DOI: (10.1016/j.eats.2016.09.003) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 3 An arthroscopic view of the right tibial anterior cruciate ligament footprint from the anterolateral portal. The center of the posterolateral (PL) tunnel position was defined as the point forward from the midpoint of both intercondylar tubercles by the radius of the PL graft. (A) Estimation of the target point with a ruler inserted from the anteromedial portal. (B) Tip aimer introduced through the anteromedial portal and located at the target point. Blue dotted line: anterior edge of the medial and lateral intercondylar tubercle; yellow circle: PL graft size. Arthroscopy Techniques 2017 6, e49-e55DOI: (10.1016/j.eats.2016.09.003) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 4 The insertion point of each guidewire is very important for preventing bone tunnel communication and posterolateral (PL) tunnel perforation to the medial articular surface. The PL and anteromedial (AM) guide pins should be inserted from the anterior border of the medial collateral ligament (MCL) and medial border of the tibial tuberosity, respectively. Red dotted line: Parsons' knob; green dotted line: medial intercondylar ridge; white dotted line: anterior horn of lateral meniscus; blue dotted line: anterior edge of the medial and lateral intercondylar tubercle. Arthroscopy Techniques 2017 6, e49-e55DOI: (10.1016/j.eats.2016.09.003) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 5 An arthroscopic view of the tibial footprint of the right knee from the anterolateral portal. The center of the anteromedial (AM) tunnel position was defined as the point separated by the radius of the AM graft from the corner of the L-shaped ridge. (A) Estimation of the target point with a ruler inserted from the anteromedial portal. (B) Tip aimer introduced through the anteromedial portal and located at the target point. (C) Two guide pins were adequately located within the anatomical anterior cruciate ligament tibial footprint. (D) Postoperative axial 3-dimensional computed tomography image of the tibial plateau. Two tunnels were successfully created. Red dotted line: Parsons' knob; green dotted line: medial intercondylar ridge; arrowheads: L-shaped ridge; blue circle: AM graft size. Arthroscopy Techniques 2017 6, e49-e55DOI: (10.1016/j.eats.2016.09.003) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions