Introduction

Femoral INTRAFIX, first introduced in 2009, is a polyethylene sheath and Polyether ether ketone (PEEK) interference screw anchor based on the design of Tibial INTRAFIX ( Fig. 73.1 ). It provides aperture fixation, is stronger and more rigid than interference screw fixation alone, and prevents graft “wind-up” by the interference screw during insertion. By virtue of its two-channel design the surgeon can separate the graft into two bundles and precisely position them within the femoral tunnel to replicate the anteromedial (AM) and posterolateral (PL) footprint ( Fig. 73.2 ). This feature, when used in conjunction with Tibial INTRAFIX, allows for the creation of a single-tunnel, double-bundle graft construct that is short, stiff, and approximately the length of the native anterior cruciate ligament (ACL) between fixation points.

Femoral INTRAFIX sheath and screw.

Courtesy Depuy Mitek, Raynham, MA.

Femoral INTRAFIX is designed to separate the graft into separate anteromedial (AM) and posterolateral (PL) bundles and precisely orient them in the anterior cruciate ligament (ACL) footprint by eccentrically compressing each bundle against the tunnel wall.

Courtesy Depuy Mitek, Raynham MA.

Graft Preparation: Autograft

Graft preparation is a critical component of the procedure and is described in part elsewhere in this publication in Chapter 81 . The overall length of each single strand of the graft should be 110 mm in small- to average-sized patients and 120 mm in larger patients. This allows for 27–30 mm of each doubled-over bundle to be seated into the femoral tunnel, 25–35 mm of graft within the joint, and 35–50 mm of graft to be contained in the tibial tunnel, with a small amount of excess graft to allow for backup tibial fixation where deemed necessary.

The graft is placed under tension, the middle of the graft marked with a pen, and an additional mark made in both directions, 30 mm away from the midpoint. A “Roman sandal” suture is then created on both sides of the midpoint. This creates a two-stranded graft over this 60-mm segment. One side of the prepared graft will be the AM bundle and is colored with a pen to differentiate it from the PL bundle for positioning later. The graft is then looped over a #5 passing suture and placed back under tension and wrapped with a moistened sponge.

Graft Preparation: Allograft

Allograft preparation is similar when using sizes similar to those of autografts. Large allografts, such as anterior tibialis and peroneus longus, are often of sufficient size to be used alone as a double-stranded graft, especially in smaller patients. In this case, graft preparation is simplified, with placement of whip sutures at the two graft ends and the Roman sandal central suture as described previously.

The authors recommend against using a soft tissue allograft larger than 10–11 mm in diameter after constructing the graft per previously described. This is because healing of allografts is delayed compared with autografts and may require even longer with larger-sized tissue, and because graft impingement of an excessively large graft may occur.

Graft Preparation: Autograft

Graft preparation is a critical component of the procedure and is described in part elsewhere in this publication in Chapter 81 . The overall length of each single strand of the graft should be 110 mm in small- to average-sized patients and 120 mm in larger patients. This allows for 27–30 mm of each doubled-over bundle to be seated into the femoral tunnel, 25–35 mm of graft within the joint, and 35–50 mm of graft to be contained in the tibial tunnel, with a small amount of excess graft to allow for backup tibial fixation where deemed necessary.

The graft is placed under tension, the middle of the graft marked with a pen, and an additional mark made in both directions, 30 mm away from the midpoint. A “Roman sandal” suture is then created on both sides of the midpoint. This creates a two-stranded graft over this 60-mm segment. One side of the prepared graft will be the AM bundle and is colored with a pen to differentiate it from the PL bundle for positioning later. The graft is then looped over a #5 passing suture and placed back under tension and wrapped with a moistened sponge.

Graft Preparation: Allograft

Allograft preparation is similar when using sizes similar to those of autografts. Large allografts, such as anterior tibialis and peroneus longus, are often of sufficient size to be used alone as a double-stranded graft, especially in smaller patients. In this case, graft preparation is simplified, with placement of whip sutures at the two graft ends and the Roman sandal central suture as described previously.

The authors recommend against using a soft tissue allograft larger than 10–11 mm in diameter after constructing the graft per previously described. This is because healing of allografts is delayed compared with autografts and may require even longer with larger-sized tissue, and because graft impingement of an excessively large graft may occur.

Femoral Tunnel Preparation

The use of the accessory AM or inferomedial (IM) portal is mandatory when using Femoral INTRAFIX with the all-endoscopic method. The method for creation of this portal is described in detail elsewhere in this volume. Patient positioning should allow for flexion of the knee to at least 110 degrees.

The Femoral Aimer in the instrument set comes in three sizes. The choice of guide is based on using a drill 1 mm larger than the graft, which accommodates the added bulk from suture material while leaving a minimum 1.5-mm posterior wall. These guides have been designed to fit the flare of the femur in the over-the-top position as encountered via the AM or IM portal, and the shaft should be placed against the base of the posterior cruciate ligament, targeting the anatomical center of the femoral footprint when the knee is flexed at least 110 degrees.

The selected Femoral Guide is placed through the accessory AM/IM portal with the knee at 90 degrees of flexion and advanced to the over-the-top position while observing with the 30-degree arthroscope in the anterolateral portal. The outflow sheath is now removed from its proximal portal and repositioned in the standard AM portal to facilitate irrigant flow during the hyperflexed stages of the procedure. The knee is then slowly flexed to 110–120 degrees, and the Femoral Aimer is kept tightly onto the femur in the over-the-top position. The appropriate guidewire (provided with the instrumentation disposable pack) is then placed through the Femoral Aimer and directed toward the desired point according to preference of the surgeon. We recommend placing the guidewire at or just proximal to the bifurcate ridge toward the AM bundle of the ACL footprint.

When the position is felt to be satisfactory, the guidewire is drilled through the lateral femoral cortex but not the skin. Note where the skin is tented, and if it is at or just anterior to the midlateral line of the thigh and 15–20 cm proximal to the lateral joint line, then the tunnel position should be satisfactory. If the guidewire tents the skin too posteriorly, the knee is not adequately flexed and the pin should be redrilled after the knee is repositioned to avoid posterior tunnel wall blowout and a tunnel that is too short.

After the guidewire is placed satisfactorily, the appropriate reamer is advanced past the femoral condyle by hand, under direct visualization with the knee maintained in the same degree of flexion used for the guidewire insertion. The reamer is then drilled to a depth of at least 27 mm by monitoring the graduations marked on the reamer shaft.

If the knee is small, the surgeon may have to penetrate the lateral cortex to obtain a depth of 27 mm, which is necessary to accommodate the Femoral INTRAFIX sheath and screw. Broaching the lateral cortex is not contraindicated but can be problematic if the graft is pulled too deeply into the femoral tunnel and out beneath the iliotibial band during graft passage.

The tunnel position is checked after clearing the bony debris to be sure the posterior wall is intact and the tunnel has been placed exactly where desired. A passing suture can now be placed when ready to pass the graft.