Preservation of the Anterior Cruciate Ligament: Surgical Techniques

Addition of Internal Brace

Over the last few years, the senior author has added an internal brace (FiberTape, Arthrex) to the repair technique, which was first performed by MacKay and colleagues.⁸ The added internal brace protects the repair and the healing process in the first few weeks and enables early ROM.

With this technique, the previously described arthroscopic primary repair technique is performed with suturing of both bundles. However, after punching, tapping, or drilling a hole in the anteromedial origin of the femoral footprint, the anteromedial anchor is first loaded with the FiberTape in addition to the repair stitches. After placing the anteromedial suture anchor in the femoral footprint, the internal brace is fixated proximally with the suture anchor into the femoral wall.

After the normal placement of the posterolateral suture anchors and completion of the repair, the internal brace has to be fixed distally. An ACL guide is used to drill a 2.4-mm drill pin up through the tibia from the anteromedial cortex (Figure 2A) and into the anterior half of the ACL tibial insertion. This is then switched for a Straight Microsuture Lasso (Arthrex) (Figure 2B), and the nitinol wire is retrieved out of the anteromedial portal with the 2 ends of the FiberTape. The FiberTape is then shuttled along the ACL substance anteriorly and down through the tibia (Figure 2C) where it fixed with a vented suture anchor near full extension after cycling the knee.

Others, however, have advocated fixing the internal brace independently of the repaired ligament and suture anchors.⁹ With this technique, tunnels are drilled in the femur and tibia and the internal brace construct is fixed proximally using a RetroButton (Arthrex) and fixed distally in the tibial metaphysis using a suture anchor. A disadvantage of this technique is that an extra femoral tunnel needs to be drilled, which is especially important in pediatric patients with the increased risk for growth disturbances.¹⁰

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the anteromedial or posterolateral bundle is a type I tear with good or excellent tissue quality, whereas the other bundle is not a type I tear or has poor tissue quality (Figure 3A). In these cases, a primary repair of one bundle is performed with a hamstring reconstruction of the other bundle.

First, a No. 2 FiberWire is used to make 4 to 5 passes from distal to proximal, as previously described. Then, the remnants of the irreparable bundle are debrided (Figure 3B). Subsequently, the semitendinosus tendon is harvested in standard fashion, or soft tissue allografts can be used.

Tunnels are then drilled for the reconstruction of the second bundle. The femoral tunnel, really a socket, is drilled at the femoral origin of the irreparable bundle using a FlipCutter (Arthrex) (Figure 3B). The tibial tunnel is localized using standard ACL guides, and drilled retrograde bicortically over a guide wire up into the ACL footprint of the bundle that is going to be reconstructed. Care must be taken to avoid damaging of the remnant that is being preserved. The sutures of the repaired remnant are then pulled back through the tibial tunnel and the repair stitches are passed through the TightRope RT (Arthrex) button. Once this is completed, all sutures and the button are passed up through the tibial tunnel and into the femoral socket. The proximal button is then flipped to engage the lateral femoral cortex in standard fashion (Figure 3C). Care should be taken to not tension the repairable remnant during the passage of the sutures through the femoral socket, as too much tension can cause tears in the remnant. Once the doubled hamstring graft has been advanced up into the femoral tunnel using the cinch stitches, the remnant bundle can then be tensioned towards the femoral wall (Figure 3D), and the sutures are tied over the TightRope RT button. Finally, the knee is cycled and held near full extension, while a BioComposite interference screw (Arthrex) is placed in the tibial tunnel for distal fixation.

Type II Tears: Augmented Repair

In patients with type II tears, primary repair is not possible as the length of the remnant is too short to firmly approximate the remnant towards the femoral wall (75%-90% of native tissue length) (Figure 4A). In these patients, an augmented repair of the entire ACL is performed using hamstring autograft or soft tissue allograft.

With this technique, repair stitches are passed into the anteromedial bundle of the remnant as previously described (Figure 4B). Keeping the repair stitches anteriorly in the anteromedial bundle tends to prevent entanglement during graft passage later in the case.

In some cases, it can be noted that the remnant has scarred to the femoral wall or the femoral notch. Crain and colleagues¹¹ previously described that in 20% of the cases, the remnant was reattached to the notch or the lateral wall of the notch. Because the reattachment is not at an anatomical position, the ligament should be detached from the femoral wall to allow the repair to be placed anatomically. In these cases, the senior author leaves the bundle initially attached to the femoral wall in order to make the passage of sutures through the ligament easier, and then he detaches the ligament to restore the anatomy.

Once the repair stitches are in place, a small accessory stab incision is made just above the medial portal. The repair stitches are parked here to keep them out of harms way. Traction on the repair stitches will retract the ACL away from the lateral wall of the notch and allow work to be performed here. A small opening notchplasty is generally performed to enhance visualization and to add a bleeding surface for enhanced healing. Next, the arthroscope is placed into the medial portal, which allows the femoral guide to be placed into the lateral portal. The femoral guide is positioned to optimize the femoral tunnel location in the center of the footprint. A small incision is made laterally over the condyle and through the iliotibial band to allow access to the lateral cortex of the lateral femoral condyle. The FlipCutter is then used to back-cut the femoral socket as described above. A FiberStick (Arthrex) passing suture is then placed in the femoral tunnel and brought out through the anteromedial portal.

Next, the tibial tunnel is drilled with a tibial guide at 55° inclination. The pin is drilled up into the center of the tibial footprint and this is over-reamed with a reamer. The reaming is stopped precisely upon breaking to proximal tibial cortex so as to minimize soft tissue damage of the ACL insertion fibers that are typically pristine. Then, a grasper is passed up and through the tunnel to retrieve the repair stitches and bring them out distally for later use. At the same time, the passing suture in the femoral is also retrieved distally. The soft tissue graft is proximally prepared with a TightRope RT button, and the repair stitches are passed through the button. The passing suture from the femoral socket is then used to shuttle the draw sutures and repair stitches up through the tibia, through the ACL remnant, and out the femoral socket (Figure 4C). The TightRope RT button is then engaged on the lateral femoral cortex in standard fashion. Using the cinch stitches, the graft is delivered through the tibia, up and through the center of the ACL remnant, and into the femoral socket. The knee is then cycled and the graft is tensioned distally in standard fashion, and fixed using a BioComposite interference screw. Finally, the repair stitches can be tensioned pulling the ligament remnant up as a sleeve around the hamstring graft (Figure 4D). They are then tied over the TightRope RT button using alternating half hitches tied with a knot pusher from laterally.