The femoral tunnel in anterior cruciate ligament (ACL) reconstruction can be created using transtibial, anteromedial portal, or outside-to-in techniques. The outside-to-in technique is less commonly performed because it requires an additional incision on the distal lateral aspect of the femur. In the transtibial technique, the femoral tunnel is drilled through the tibial tunnel and through the anteromedial portal in the anteromedial portal technique. The anteromedial portal technique allows femoral tunnel drilling independent of the placement of the tibial tunnel.
Recent studies have shown the superiority of the anteromedial portal technique over the transtibial technique. The anteromedial portal technique may more accurately position the femoral tunnel in the center of the ACL femoral footprint than the transtibial technique (Figure 1).1–5 Anteromedial portal drilling may lead to improved Lachman and anterior drawer tests, although clinical results have not been shown to be significantly different.1
Figure 1: Femoral tunnel location via the medial portal technique (M) compared with the transtibial technique (T).
Although the popularity of the anteromedial portal technique is growing, many surgeons are uncomfortable changing from the transtibial technique. Anteromedial portal drilling requires knee hyperflexion during use of the drill guide, guidewire, and cannulated drill, which is awkward and requires an additional assistant to stabilize the knee in hyperflexion during this critical surgical step.
The figure-4 position is a standard knee arthroscopy position most knee arthroscopists are comfortable with that can be used to easily obtain the necessary hyperflexion for femoral tunnel creation via the anteromedial portal. To the author’s knowledge, anteromedial portal femoral tunnel drilling in the figure-4 position has not been previously described.
Materials and Methods
Twenty consecutive patients underwent ACL reconstruction with patellar tendon autograft using the anteromedial technique in the figure-4 position. Mean patient age was 22.5 years (range, 15–34 years). Eleven patients were women, and 9 were men. All patients were followed for a minimum of 4 months postoperatively.
The patient is positioned supine in slight Trendelenburg with the lower portion of the operating table in full flexion. The knee is flexed at the bend of the operating table (Figure 2). A curved lateral knee post is used. A thigh tourniquet is placed. The anteromedial portal is placed 1 cm medial to the patellar tendon and 1 cm superior to the joint line. The anterolateral portal is placed immediately lateral to the patellar tendon and 1 cm superior to the joint line.
Figure 2: Photograph of knee positioning in anterior cruciate ligament reconstruction.
Treatment of meniscal or chondral pathology and an assessment of the ACL are first performed arthroscopically. The tourniquet is raised after exsanguination, typically to 350 mm Hg. Harvest of the central one-third of the bone–patellar tendon–bone autograft is then performed. The ACL stump is debrided, and a lateral notchplasty is performed as needed. The tibial tunnel is drilled from outside-to-in with the knee at 90° of flexion. The tibial tunnel is placed 7 mm anterior to the posterior cruciate ligament at the center of the tibial ACL footprint.
The femoral tunnel position is marked with a curet at the 10-o’clock position on the wall of the femoral notch at the center of the femoral ACL footprint with the knee at 90º of flexion. The knee is then flexed to 120º in the figure-4 position. A well-padded Mayo stand is used to stabilize the leg in the figure-4 position. The foot is inverted by an assistant to stabilize the knee in hyperflexion (Figure 3). The 7-mm offset femoral aimer is placed through the anteromedial portal and positioned at the previously marked femoral tunnel position (Figure 4). The femoral guidewire is placed and overdrilled with a cannulated acorn drill (Figure 5). The acorn drill is initially advanced 10 mm and then backed up to confirm maintenance of the posterior femoral cortex. The drill is then further advanced to a depth of 25 mm (Figure 6). Loose debris from the aperture of both tunnels is debrided with a shaver and an arthroscopic grabber.
Figure 3: Photograph of the figure-4 position with 120° of knee flexion and the foot held in inversion.
Figure 4: Photograph of the 7-mm offset guide placed through the anteromedial portal with the knee hyperflexed in the figure-4 position (A). Arthroscopic image of the 7-mm offset guide positioned at the femoral anterior cruciate ligament footprint (B). Diagram of the 7-mm offset guide positioned at the femoral anterior cruciate ligament footprint (C).
Figure 5: Arthroscopic image of the femoral guidewire in place at the 10-o’clock position (A). Diagram of the femoral guidewire placed at the 10-o’clockposition (B).
Figure 6: Arthroscopic image of the femoral tunnel is created at the 10-o’clock position on the wall of the femoral notch (A). Diagram of femoral tunnel created at the 10-o’clock position via the anteromedial portal (B).
The passing beath pin is placed through the femoral tunnel via the anteromedial portal and retrieved on the distal lateral aspect of the thigh. A #2 nonabsorbable passing suture is looped in the eyelet of the beath pin and brought through the femoral tunnel via the anteromedial portal (Figure 7). A guidewire for the femoral interference screw is placed through the anteromedial portal into the femoral tunnel. The passing suture is retrieved through the tibial tunnel with the knee flexed to 90º (Figure 8). The suture is used to pass the graft through both tunnels at 90º of flexion (Figure 9). The knee is again placed in the figure-4 position for placement of the cannulated femoral interference screw through the anteromedial portal. The tibial interference screw is placed with the knee flexed to 30º and with a posterior drawer force applied to the knee (Figure 10).
Figure 7: Diagram of the passing beath pin passed through the femoral tunnel via the anteromedial portal and used to pass the passing suture.
Figure 8: Diagram of the passing suture retrieved through the tibial tunnel.
Figure 9: Diagram of the passing suture used to pass the graft through the tibial and femoral tunnels.
Figure 10: Arthroscopic image of the final anterior cruciate ligament reconstruction with the graft in place.
In all 20 cases, the femoral tunnel was consistently placed at the 2-o’clock position on the wall of the femoral notch. No patient had significant intra- or postoperative complications. No cases were complicated by femoral wall blowout. All patients reported excellent results at final follow-up.
Femoral tunnel creation via the anteromedial portal requires knee hyperflexion to achieve the proper drilling angle. Knee hyperflexion in the axial plane during ACL reconstruction is awkward and difficult to achieve. The lower portion of the standard operating table typically blocks knee flexion past 100º. Therefore, knee hyperflexion requires flexion at the hip, which necessitates removal of knee holders or other obstructions to hip flexion. An assistant is required to hold the knee in hyperflexion, and the operating table must be lowered to allow the surgeon to be properly oriented to the knee. Therefore, many surgeons are uncomfortable with the technical difficulty associated with anteromedial portal drilling and the necessary knee hyperflexion.
The figure-4 position is commonly used in routine knee arthroscopy to gain access to the lateral compartment of the knee. This position is simple to obtain and highly reproducible. Hyperflexion of the knee up to 120º can be easily achieved in the figure-4 position. The Mayo stand is used to stabilize the leg in this position and can be raised or lowered to adjust knee flexion and varus stress on the knee. The foot is stabilized in inversion by the assistant to maintain stable knee hyperflexion.
The femoral tunnel can be created through the anteromedial portal using the figure-4 position. Most knee arthroscopists are comfortable with the figure-4 position and do not need to make adjustments to the operating table setup to accommodate this technique. Anteromedial portal femoral tunnel drilling in the figure-4 position is a useful alternative in ACL reconstruction.
Knee hyperflexion in the figure-4 position allows simple, reproducible femoral tunnel drilling through the anteromedial portal.
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