ABSTRACT: Although the transtibial (TT) technique for single-bundle (SB) arthroscopic anterior cruciate ligament (ACL) reconstruction has been widely used, surgeons often disadvantageously create the femoral bone tunnel at the arthroscopically noon position, which is alleged the “ACL isometric point,” when the femoral bone tunnel could be created behind the resident’s ridge with TT-SB ACL reconstruction by paying attention to the location of the tibial tunnel inlet and the angle of tibial tunnel. This alternative approach preserves ACL remnant tissue, which might contribute to better postoperative remodeling and regeneration of proprioceptive mechanoreceptors. This technique reduces surgical invasiveness and can enhance postoperative graft remodeling and proprioceptive recovery. To successfully use the devices required for this procedure, surgeons must understand the proper techniques. Hence, this technical note aims to demonstrate TT-SB ACL reconstruction with remnant tissue preservation. Technique Video Video 1 Anterior cruciate ligament (ACL) reconstruction is carried out under regional or general anesthesia without a pneumatic tourniquet. The patient is placed in a supine position with the operative knee held in the leg drop position at 90° flexion. Standard anterolateral and anteromedial portals are made. After routine arthroscopic observation, the ACL remnant tissue is pulled with a probe and confirmed to be Crain type 3. The proximal end of the remnant femoral stump located behind the resident’s ridge is minimally debrided using a shaver, and a thermal device is used to create the femoral bone tunnel. During this procedure, careful attention should be made to the ACL remnant tissue so that it is not injured and to preserve the continuity and maximize the amount of ACL remnant tissue. Anatomic insertion of the femoral anteromedial bundle (AMB) is identified behind the resident’s ridge via the anteromedial portal. Then, a longitudinal slit is made at the center of the tibial ACL remnant tissue, into which the tibial ACL guide is inserted. The center of the tibial bone tunnel is placed at the AMB footprint from the lateral to the medial tibial spine. The center of the AMB insertion is defined according to 3 surrounding landmarks, namely, the anterior ridge, lateral groove, and intertubercular fossa, and bony prominences corresponding to the ACL tibial footprint are identified. The coronal angle relative to the tibial axis averages 25.5°, and the sagittal angle relative to the tibial axis was averages 52.3°. Then, a tibial tunnel with a diameter of 8.5 to 9 mm is made. The femoral bone tunnel insert is positioned inferior to the “over-the-top” position. The 6-mm femoral aimer is inserted through the tibial tunnel to prevent posterior wall blowout with varus and internal rotation of the tibia, thus resulting in a figure-four position. Hence, the femoral bone tunnel is created lower and deeper, thus placing it behind the resident’s ridge. The 2.4-mm guide pin insertion point is confirmed via anteromedial portal considering the location behind the resident’s ridge. Then, 4.5-mm arthroscopic drilling accompanied by an 8-mm over drilling is performed to create a socket-shaped tunnel. When the femoral tunnel cannot be created behind the resident’s ridge, surgeons should consider creating a femoral tunnel using the outside-in technique or transportal technique. The length of the femoral bone tunnel is measured using a depth gage and the length of suspensory fixation device is calculated. A hamstring graft is introduced into the joint cavity through the tibial tunnel and ACL remnant tissue and then placed in the femoral socket.
