In standard ACL reconstruction, even an ACL remnant that bridges the femur and tibia should be debrided to create the femoral and tibial tunnels. However, it has been proven that these remnants conserve the neuroreceptors and mechanoreceptors, which is beneficial to joint position sense after surgery. Adachi et al  observed a positive correlation between the number of mechanoreceptors and the accuracy of joint position sense. The authors even found mechanoreceptors in patients having a long interval between the ACL injury and the surgery and concluded that surgeons should consider preserving ACL remnants during ACL reconstruction. Additionally, as far as revascularization of the grafted tendon is concerned, an ACL remnant with abundant vascularity can provide a favorable influence allowing swifter "ligmentization" of the graft [1, 2, 5, 15, 17, 18].
Crain et al  also proved that resection of the ACL remnants, especially those healed to the femur effectively crossing the joint, resulted in a measurable increase in passive anterior laxity in a group of ACL-deficient knees.
Noyes et al  reported that in up to 50% of all cases, partial ACL lesions develop into full ligament ruptures, primarily as a result of vascular interruption and necrosis of the fibers following their rupture. Consequently, this type of lesion will sooner or later develop into a full rupture of the ACL, or at the very least force the patient to adopt a lower level of activity.
Augmentation reconstruction is performed in case of partial rupture of the ACL by creating a tunnel that complements the ACL remnant in the native femoral anatomical attachment site. Ochi et al  demonstrated the favorable clinical results of the augmentation reconstructive surgery of the ACL using a 1-incision technique. On the other hand, if the ACL remnant is not of considerable thickness, or not bridging the femur and the tibia, remnant preserving double bundle ACL reconstruction can be performed.
Our technique comprises the creation of a longitudinal slit in the ACL remnant fibers. This would allow the visualization of the tip of the guide wire used for preliminary drilling of the tibial tunnel. We also used the transverse intermeniscal ligament as a landmark for creation of the AM tibial tunnel. This would allow for the creation of the tibial tunnels within the native ACL tibial foot print under direct vision without the need to use the image intensifier for tibial tunnel localization. Moreover, reconstruction of the femoral tunnels using the FAM portal independent from the tibial tunnels allow increasing the angulation of the tibial tunnels from 45° to up to 65° to maximize visualization of the tip of the guide wire. Also making a passage using a curved hemostat through the slit in the ACL remnant reaching the intra articular aperture of the femoral tunnel avoids impingement of the reconstruction graft against the ACL remnant and avoids notch overstuffing and the development of cyclops lesion. The biological potential for graft ligamentization is optimized by our technique of suturing the highly vascularized synovial folds over the reconstructed graft-remnant composite [19, 20].
During creation of an anatomical tibial PL tunnel with remnant preservation, especially if this remnant is bridging between the femur and the tibia (Group 2), it would be impossible to visualize the tip of the guide pin without making a longitudinal slit in the ACL remnant. The latter would also allow the passage of the PL graft through the remnant with minimal impingement against it. In that case also the AM reconstruction graft can be placed above the ACL remnant. On the other hand, if the ACL remnant is not bridging between the femur and the tibia (Group 1) e.g connecting the tibia to the roof of the intercondylar notch, in that case making a longitudinal slit through the remnant would allow anatomical creation of AM and PL tibial tunnels through the ACL tibial foot print by allowing visualization of the tip of the guide pins used for preliminary drilling of such tunnels, especially if this is coupled with mild increase of the slope of the tibial tunnel from 45 up to 65°.
In this study, the FAM was used to create the femoral tunnels, while viewing through the central anteromedial portal. This resulted in the creation of a femoral tunnel within the anatomic femoral ACL attachment independent of the tibial tunnel. This goes with the findings of other authors who recommended the use of the far anteromedial portal for anatomical creation of the femoral tunnels [4, 5, 9–13]. However, we added a step of using 3D CT for preoperative prediction of the optimal site of the incision for the FAM portal that allows creation of the femoral tunnels with optimal length and orientation and within the confines of the anatomical ACL footprint meanwhile without damaging the articular cartilage of the medial femoral condyle.
The resident's ridge is arthroscopically identifiable, and is a useful landmark for anatomical femoral tunnel drilling in arthroscopic ACL reconstruction. The main part of the femoral attachment of the ACL is on the resident's ridge, and the remaining part is attached to the posterior portion of the ridge. Creation of the femoral tunnel just on the ridge is theoretically right. However, in ACL reconstruction using hamstring tendons, the center of the femoral tunnel opening is not the central point of application of force, because the graft is pulled to anterior direction. Therefore, we create the femoral bone tunnel just behind the resident's ridge through the far anteromedial portal.
In the future, both short term and long term prospective as well as retrospective clinical studies may be needed to prove the theoretical biological as well as biomechanical advantages of our procedure comprising anatomical double bundle ACL reconstruction, meanwhile with ACL remnant preservation.