Single Bundle versus Double Bundle Techniques

The femoral side is almost always addressed arthroscopically, although two major techniques, the single bundle and the double bundle, are possible. Early reconstructive techniques, which focused on placing a single femoral tunnel in the "isometric" region of the native PCL, were found to produce abnormal knee kinematics, especially when the knee flexed more than 45 degrees.20 Only 5% to 15% of the femoral footprint is truly isometric, and therefore current single-bundle methods have been modified to place the femoral tunnel in the anterior aspect of the footprint to reproduce only the structurally superior antero-lateral bundle.

With the patient supine, a 2-cm incision over the anterior knee is necessary and should be placed just medial to the articular edge of the trochlear groove and distal to the vastus medialis obliquus. The retinaculum is incised in line with the skin incision. The proximal portion of the femoral tunnel guide is positioned midway between the patella and medial epicondyle, at least 1 cm from the patellofemoral articular edge to ensure that the joint is not violated. The tip of the drill guide is placed through the medial portal onto the anterior half of the femoral PCL footprint, 8 to 9 mm above the articular surface. The guide pin should be driven with the knee in 70 to 90 degrees of flexion and exit high in the notch at the 11- or 1-o'clock position (for left or right knees, respectively) within the anterior half of the anatomic footprint.10,16 The tunnel is then created by drilling over the wire. Most authors drill the femoral tunnel outside-in in this manner, although an inside-out technique has also been described using an accessory anterolateral portal. It is suggested that this latter method may lead to a more acute, and therefore less favorable, angle between the intra-articular graft and bony tunnel, resulting in fraying and graft wear if the tunnel entrance is not carefully chamfered21 (Fig. 53-12).

Because the PCL exhibits a very small zone of isometric fibers, only anatomic reconstructions can accurately restore native function.21 Reconstruction of only the AL bundle may over time allow graft elongation secondary to nonuniform distribution of forces across the graft. To improve the success of reconstruction, some surgeons have added a second bundle to better replicate the native PCL orientation and provide a more uniform load distribution.20 Theoretically, a two-bundle technique offers a biomechanical advantage and is superior to single-

Figure 53-12 Postoperative radiographs of a single-bundle posterior cruciate ligament reconstruction. (From Allen CR, Rihn JA, Harner CD: Posterior cruciate ligament: Diagnosis and decision making. In Miller MD, Cole BJ [eds]: Textbook of Arthroscopy. Philadelphia, WB Saunders, 2004, pp 687-702.)

Figure 53-13 Anatomic position of femoral tunnels for single-bundle (anterolateral [AL] only) or double-bundle (AL and posteromedial [PM]) posterior cruciate ligament reconstruction. (From Allen CR, Rihn JA, Harner CD: Posterior cruciate ligament: Diagnosis and decision making. In Miller MD, Cole BJ [eds]: Textbook of Arthroscopy. Philadelphia, WB Saunders, 2004, pp 687-702.)

Figure 53-13 Anatomic position of femoral tunnels for single-bundle (anterolateral [AL] only) or double-bundle (AL and posteromedial [PM]) posterior cruciate ligament reconstruction. (From Allen CR, Rihn JA, Harner CD: Posterior cruciate ligament: Diagnosis and decision making. In Miller MD, Cole BJ [eds]: Textbook of Arthroscopy. Philadelphia, WB Saunders, 2004, pp 687-702.)

tubercle through a longitudinal 2- to 3-cm incision. This results in a trajectory of 50 to 60 degrees to the long axis of the tibia, creating a graft orientation at the posterior tibia of approximately 45 degrees. This reduces the effects of the "killer turn," a term referring to the sudden bend that the graft must take as it passes from the tunnel into the knee joint.10 The anterior skin incision can also be placed lateral to the tubercle, which may further reduce graft angulation.21 It has been recommended that one make a 2-cm safety incision posteromedially, which will allow access for the surgeon's finger to directly protect the neurovascular structures and monitor any instruments placed in posterior knee10 (Fig. 53-14). A guidewire is drilled under arthroscopic visualization, and a 10- to 12-mm tunnel then drilled over the wire, taking care to protect the neurovascular structures at all times because, even with the knee flexed 90 degrees, the distance between the popliteal artery and posterior tibia is less than 1 cm. (Because of this, the inlay technique should be avoided in patients who have had recent or remote vascular repairs, which causes increased scarring and altered anatomy in the posterior knee.) The posteromedial portal and fluoroscopy may be used for direct observation during this step. The final drilling of the posterior cortex should also be completed by hand. The edge of the tibial tunnel must be chamfered to avoid excessive graft wear at the turn (Fig. 53-15).

bundle methods because it replaces both major portions of the native PCL. As each bundle is tensioned at the appropriate degree of flexion, this technique may decrease posterior laxity and better restore normal knee biomechanics through a greater range of knee motion.14,22 Proper placement of this second bundle is critical, however, as position greatly affects the tension of the AL bundle. A middle or distal second bundle allows cooperative load sharing and decreases anterior bundle tension, but proximal placement of the second bundle may not alter peak anterior bundle tension.20 Clinical studies have not yet consistently demonstrated improved resistance to posterior translation or improved in vivo joint kinematics between the two techniques.5,14

Although technically more challenging, the two-bundle method is similar to the single tunnel except for the fact that two femoral tunnels are drilled, one for the AL bundle in the anterior half of the femoral footprint and a smaller tunnel posteriorly (Fig. 53-13). Both grafts are routed through same tibial tunnel or can originate from the same tibial bone block. Again, the tunnel for the AL band is centered at the 1-o'clock position (for right knee), 2 to 3 mm behind the condylar articular margin, while the tunnel for the PM band is centered on the footprint at about 3:30-o'clock position.

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