A guidepin is then placed and drilled out through the lateral femoral cortex. The tunnel distance is measured as the guidepin is pulled back and marked. The guidepin is then advanced and we ensure that the pin is not aimed posteriorly towards the neurovascular structures but rather in the midshaft or exiting anterior to that. A standard reamer, fluted reamer or half reamer may be used to then drill the socket to the predetermined depth, must take great care not to violate the articular cartilage of the medial femoral condyle. The half fluted reamers are very helpful in this regard.

Tibial guide placement and creating a tibial socket: The Retrodrill Tibial Guide System (Arthrex) facilitates precise placement of the tibial tunnel. The fixed angle guide may be inserted in either the low anteromedial portal or the high central anteromedial portal, depending upon the patient’s anatomy and ease of placement. The guide is aimed so that the exiting guidepin comes in precisely at the anatomic center of the tibial footprint which is often approximately about 7 mm anterior to the posterior cruciate ligament. In addition, it is important that the guide be angled so that it will aim towards the femoral tunnel as well and not simply be placed as far posteriorly as possible or placed in such a way where it comes out directly on the medial tibial spine. In fact, because of the retro- screw construct, screw placement will be easier if the socket created is in fact in the anatomic center of the ACL which is somewhat anterior to the edge of the notch. The transtibial retrodrill guidepin is inserted through the skin percutaneously just medial to the tibial tubercle, and while advancing the pin under forward direction, the preassembled appropriate sized retrocutter is then captured within the joint.

Forward drilling with the retrograde reamer creates an all-inside socket. The potential length of the socket could be determined by reading the marks on the drill guide bullet and by tactile sensation which comes about abutting the distal tibial cortex. We generally drill a socket length between 30 and 40 mm depending upon the anatomy, size of the patient and the graft length that we have by precisely recording the available socket length available by reading the guides bullet arm and subsequently recording the amount of socket drilled by using the grommet on the guidewire, one can avoid penetrating the tibial cortex. When the desired depth is met, the retro reamer is advanced in an antegrade fashion until the docking station is approached at which point the drill is placed unreversed and a retro cutter is then affixed to the superior arm of the guide and atraumatically removed from the joint. After the sockets have been drilled, thorough arthroscopic lavage is performed and all loose debris is removed. Graft selection and preparation of allograft tissue allows for essentially no incision “all arthroscopic technique”. We often prefer to use autogenous patellar tendon and tibial tubercles sparing the patellar bone, however any graft option is possible with this technique. When allograft tissue is used, we create sockets to match the exact graft tissue size. Graft length is essential while performing this procedure. The graft length not exceeds the combined intraarticular distance and femoral tibial socket lengths to prevent bottoming out of the construct and not obtaining correct graft tension.
Allografts are prepared prior to the arthroscopic surgery. We utilize 75-mm graft length for an average-sized knee. We do modify this and will create a somewhat smaller construct for a petite gymnast for instance and yet create an appropriate longer construct for a professional football player. The rationale for choosing the graft length is as followed. The intraarticular distance of the reconstructed ligament based upon the methods we described is approximately 27 to 35 mm. The minimum socket length we obtained on the femur is approximately 22 mm while the minimum socket length on the tibia is at least 30 mm. Therefore, under these assumptions, the graft length has to be approximately 82 mm or less, allowing for approximately 5-7 degrees of leeway, we back down to a 75 mm graft and in this way have never had an episode of bottoming out or not having sufficient length within either the femoral or tibial sockets to allow excellent fixation. Graft passage and fixation, once tunnels have been created, graft fashioned appropriately, a standard Beath pin is utilized to pass the femoral portion of the graft, alining either the soft tissue or bony portion of the graft within the socket to allow for later joint line fixation. To allow for tibial side graft passage and preparation of graft fixation, a FiberWire had been placed through the cannulated guide pin and left outside the anteromedial portal. The graft sutures exiting the tibial side of the graft were then tied onto the passing FiberStick (Arthrex Naples, FL) approximately 4 cm from the end. A Nitinol guidewire (Arthrex) is then tied to the end of the passing FiberStick approximately 4 to 5 cm from the graft sutures. The FiberStick is then pulled distally through the tibial hole, and under direct visualization, the graft sutures are first retrieved with the aid of a probe or other passing instrument. The graft is then reduced under direct visualization while the guidewire is placed in an anterior to anteromedial location. After the graft is secured but not fixed in either the femur or tibia, the guidewire is then placed under direct visualization and placed appropriately anteriorly so the subsequent screw fixation is possible. Isometry may be checked at this point or one may elect to fix the femoral side of the graft as desired. We generally use a bio-interference screw fixation on a bone plug or a soft tissue interference screw in combination with an EndoButton, depending upon graft selection made. We feel it is essential to have joint line fixation at the aperture of the femoral socket taking care to position the interference screw in such a way that it does not cause impingement on the PCL, lateral wall or anterior wall of the notch. When the femoral side of the graft is then fixed, the graft is pre-tensioned and put through a range of motion and the further isometry testing may be judged. Certainly, one would be able to judge whether there is any potential interference with the PCL or the femoral notch. When graft position and femoral fixation are complete, the Nitinol wire is passed through the tibial socket and out the tibial guidewire hole percutaneously. The Nitinol wire is then removed and the retro-screwdriver is advanced over the Nitinol wire just placed and brought into the proximal end of the tibial socket under direct visualization in an anterior to slightly anteromedial configuration within the notch. Next, a FiberStick is advanced into the joint via the retro-screwdriver and retrieved through the high central anteromedial portal and then loaded with a tibial retro-screw either conventional or reverse thread. The tibial retro-screw is secured with a large mulberry knot, pulled back into the joint and carefully loaded onto the retro-screwdriver as the retro-screwdriver is advanced to the level of the joint line and a probe or grasper is placed on the top of the screw to facilitate this maneuver.

Care is then taken to advance the retro-driver up through the length of the screw so good purchase is obtainable. The graft is tensioned appropriately. A reverse procedure is performed and the tibial screw is advanced in a counterclockwise fashion (clockwise of the reverse screw is used while the retro-screw tamp) Arthrex, Naples, FL exerts an axial force downward while gently pulling this screwdriver which has the FiberStick attached to it distally until the screw advances to be flushed at the joint line. In general, we utilize a femoral screw and tibial screw diameter 1 mm less than the socket diameter. Backup fixation on the tibial side is often done with a button as this has shown to greatly increase pullout strength. We do not routinely use backup fixation on the femur for bony grafts unless bone quality or other technical factors which may have jeopardized fixation are incurred.