reviSiOn anTeriOr cruciaTe ligaMenT recOnSTrucTiOn - dealing WiTh an enlarged Tibial Tunnel

INTRODUCTION Reconstructing a torn anterior cruciate ligament (ACL) in a knee that has had prior ACL surgery presents challenges, especially if multiple procedures have been done in the past. Revision ACL surgery will continue to become more common as the number of primary ACL reconstruction procedures continues to increase. A common problem faced by the surgeon in the revision setting is an enlarged tibial tunnel [1, 2]. This problem is most commonly encountered in reconstructions with allograft, hamstring autograft, and synthetic Gore-tex grafts [3-8]. Occasionally, the bone in the proximal tibia is almost hollow after the failed graft and the interference screw have been removed. In this scenario, new interference screw fixation is not possible. Several techniques can be employed to fix the new bone plug of a bone-tendon-bone graft in an enlarged tibial tunnel. These include 1) staging the revision by first removing the hardware and filling the tunnel with iliac bone graft and delaying the insertion of the new ACL graft until the bone graft incorporates (about a year); 2) nesting more than one interference screw in the tibial tunnel; 3) post-and-washer fixation; and 4) staple fixation [4, 9-11]. We present an alternate method of internal fixation of the plug to the tibia using AO/Synthes 3.5 mm fully threaded cortical screws with a lag technique though the tendon graft. The advantages of this method include the ability to switch to this technique in the midst of an operation without change in exposure, and the ability to secure immediate fixation regardless of the size of the tibial tunnel. TECHNIQUE Using an osteotome and ronguer, the anterior cortex of the tibia is removed to expose the anterior part of the bone plug and to deepen the tunnel into a trough. The graft is pushed into the trough so that it is buried below the anterior surface of the tibia. While applying tension to the graft with the knee in extension, a drill hole is made through the bone plug and underlying tibia. The drill bit is left in place. A second drill hole is made through the plug parallel to the first drill hole. An AO/Synthes 3.5 mm fully threaded cortical screw is then inserted into the second drill hole using a lag technique to create compression across the graft. The first drill bit is then removed and another cortical screw is inserted into the first drill hole. Both screws should obtain purchase in the posterior cortex of the tibia in order to generate compression across the graft. This technique may be employed with or without the use of washers. This method is difficult to employ if the graft is short and works best if the graft is too long, protruding from the tibial tunnel. CASE REPORTS We describe two patients who have undergone revision ACL reconstruction with the currently described technique used for tibial tunnel fixation.