Anatomic Femoral Tunnel Placement Research Articles

Paper # 188: Can You Achieve Anatomic Femoral Tunnel Placement with Transtibial Anterior Cruciate Ligament Reconstruction Using Smaller Tunnel Sizes?

Paper # 188: Can You Achieve Anatomic Femoral Tunnel Placement with Transtibial Anterior Cruciate Ligament Reconstruction Using Smaller Tunnel Sizes?

Comparison of ACL Fixation Devices Using Cadaveric Grafts

We evaluated two newer forms of femoral fixation of hamstring grafts for anterior cruciate ligament reconstruction, the Endobutton direct (Smith and Nephew, Andover, MA) and Femoral intrafix (Depuy Mitek, Raynham, MA), and compare them to devices that have been evaluated in the literature, the AXL Crosspin (Biomet, Warsaw, IN) and Biotransfix II (Arthrex, Naples, FL). Paired hamstring tendon allografts were fixed in the femoral tunnel of 24 cadaveric bovine knees (6 per group) according to each device's specifications. The free ends (tibial sides) were fixed to the materials testing machine via custom-made cryo-clamps. In Phase I, single load to failure and stiffness were evaluated, and in Phase II, peak displacement was evaluated while cyclic loading was performed over 1000 cycles. One-way analyses of variance were performed to test for differences between groups. There were no significant differences in failure load (p = 0.42) or stiffness (p = 0.39) between the fixation devices. There was also no significant difference in peak displacement measured during the cyclic loading phase (p = 0.32). Our findings suggest that the newer generation devices, Endobutton direct and Femoral intrafix, have similar strength in single load to failure and similar peak displacement during cyclic loading as compared with clinically proven Crosspin techniques. These newer devices, which are designed to accommodate for more anatomic femoral tunnel placement, may provide a reasonable alternative without compromising biomechanical properties.

In vitro and in vivo AM and PL tunnel positioning in anatomical double bundle anterior cruciate ligament reconstruction

There have been few studies investigating the correct anatomical femoral and tibial tunnel placement in double bundle anterior cruciate ligament (ACL) reconstruction. To compare anteromedial (AM) and posterolateral (PL) tunnel positions in anatomical double bundle ACL reconstruction in human cadaver and patient knees. Fifteen fresh-frozen non-paired adult human knees and 27 patients (27 knees) were evaluated. In the cadaver knees, AM and PL bundles were identified by their difference in tension patterns. Their femoral centers were marked with a K-wire, and cut from the femoral insertion site. After this, each bundle was divided at the tibial side. The center of each bundle insertion was again marked with a K-wire, and 5-7-mm tunnels were drilled with transportal or outside-in technique. In patient knees, each tunnel was made according to the native ACL foot print and bony landmarks using transtibial technique (n=5) and transportal technique (n=22). Tunnel placement was evaluated using a C-arm X-ray device and 3D CT. For the femoral side assessment, Bernard and Hertel's technique was used. For the tibial side assessment, Amis and Jakob's technique was used. The femoral AM tunnel in the cadaver knees was placed in a significantly deeper position when compared to patient knees. There was no significant difference in the AM vertical placement or in the PL tunnel placement in the femur. No significant differences were observed in the tibial tunnel placements between cadaver and patient knees. In vivo positioning of the femoral AM bundle differed significantly from the in vitro positioning.

Can Anatomic Femoral Tunnel Placement Be Achieved Using a Transtibial Technique for Hamstring Anterior Cruciate Ligament Reconstruction?

Background: Recent studies have emphasized the importance of anatomic tunnel placement during anterior cruciate ligament (ACL) reconstruction in an effort to restore normal knee kinematics and stability. Secondary to the constraints imposed by a coupled drilling technique, the ability to achieve an anatomic femoral tunnel during transtibial hamstring ACL reconstruction may be limited. Hypothesis: The size limitations imposed by the small-diameter tibial tunnel used in hamstring ACL reconstruction would preclude the ability to place an anatomic femoral tunnel. Study Design: Descriptive laboratory study. Methods: In a descriptive laboratory study, fresh-frozen human cadaveric knees fixed at 90° of flexion were dissected to expose the centers of the native femoral and tibial ACL insertions. The geometry and location of each insertion were evaluated. Using a standardized starting point, tibial tunnels were drilled to the center of the tibial insertion using an 8-mm reamer. Next, a 6-mm over-the-top guide was used to position as close as possible to the anatomic femoral ACL insertion on the lateral wall, and femoral tunnels were drilled with the 8-mm reamer. For each tunnel, the location, geometry, and percentage overlap with the native insertion site were evaluated using a 3-dimensional laser scanner. Results: The reamed tibial tunnel was central within the insertion site, occupying 40.4% ± 2.0% of the native tibial insertion. Transtibial drilling resulted in femoral tunnels that were superior and posterior compared with the native femoral insertion. Thefemoral tunnel had a mean ± SD overlap of 30.0% ± 12.6% with the femoral insertion, with the center of the tunnel 7.6± 0.5 mm from the center of the native ACL femoral insertion. Conclusion: Based on our data using our specific starting point, during hamstring ACL reconstructions, the constraints imposed by a coupled drilling technique result in nonanatomic femoral tunnels that are superior and posterior to the native femoral insertion. Clinical Relevance: Anatomic femoral tunnel placement during hamstring ACL reconstructions may not be possible using a coupled, transtibial drilling approach.

Femoral Tunnel Placement During Anterior Cruciate Ligament Reconstruction

Background Recent studies have questioned the ability of the transtibial technique to place the anterior cruciate ligament graft within the footprint of the anterior cruciate ligament on the femur. There are limited data directly comparing the abilities of transtibial and tibial tunnel—independent techniques to place the graft anatomically at the femoral attachment site of the anterior cruciate ligament in patients. Hypothesis Because placement with the tibial tunnel–independent technique is unconstrained by the tibial tunnel, it would allow for more anatomic tunnel placement compared with the transtibial technique. Study Design Cross-sectional study; Level of evidence, 3. Methods High-resolution, multiplanar magnetic resonance imaging and advanced 3-dimensional modeling techniques were used to measure in vivo femoral tunnel placement in 8 patients with the transtibial technique and 8 patients with a tibial tunnel–independent technique. Femoral tunnel placement in 3 dimensions was measured relative to the center of the native anterior cruciate ligament attachment on the intact contralateral knee. Results The tibial tunnel–independent technique placed the graft closer to the center of the native anterior cruciate ligament attachment compared with the transtibial technique. The transtibial technique placed the tunnel center an average of 9 mm from the center of the anterior cruciate ligament attachment, compared with 3 mm for the tibial tunnel–independent technique. The transtibial technique resulted in a more anterior and superior placement of the tunnel compared with the tibial tunnel– independent technique. Conclusion The tibial tunnel–independent technique allowed for more anatomic femoral tunnel placement compared with the transtibial technique.

Lateral Anatomic Structures at Risk During Transepiphyseal Reconstruction of the Anterior Cruciate Ligament (SS-47)

Transepiphyseal reconstruction of the ACL allows for anatomic placement of the femoral tunnel and avoids damage to the distal femoral physis. To our knowledge there is no published study describing the lateral structures at risk during this technique. The popliteus tendon and lateral collateral ligament are at greatest risk during guide pin placement for the posterolateral bundle femoral tunnel. The lateral collateral ligament and gastrocnemius tendon are at risk during placement of the anteromedial bundle guide pin. A better understanding of the lateral knee anatomy can help avoid damage to the lateral structures during transepiphyseal ACL reconstruction. The purpose of the present study is to describe the lateral anatomic structures at risk during transepiphyseal preparation of the anterior cruciate ligament femoral tunnel. We utilized 6 fresh frozen cadaveric knees. We first excised the ACL and identified the anatomic footprints of the anteromedial (AM) and posterolateral (PL) bundles. A guide pin, oriented parallel to the ground, was then passed through the center of each bundle's footprint, exiting the lateral femoral cortex. Subsequently, the anatomic structures on the lateral aspect of the knee were exposed. We then measured the distance from the AM and PL bundle guide pins to the lateral collateral ligament, popliteus and gastrocnemius tendons. We also measured the angle of the guide pin with respect to the lateral epicondyle in the axial plane (epicondyle angle). The mean length from the AM bundle guide pin to the LCL, popliteus and gastrocnemius tendons were 0.76, 6.32, and 2.67 mm, respectively. The guide pin pierced the LCL in 2 out of 6 specimens. The gastrocnemius tendon was pierced in 1 of 6 specimens. The AM bundle mean epicondyle angle measured 15.5 degrees. The mean length from the PL bundle guide pin to the LCL, popliteus and gastrocnemius tendons were 0.72, 1.14, and 8.11 mm, respectively. The guide pin pierced the LCL in 4 of 6 specimens. The popliteus tendon was pierced in 3 out of 6 specimens. The mean PL bundle epicondyle angle measured 17.7 degrees. Anterior cruciate ligament (ACL) reconstruction in the preadolescent patient is becoming more commonplace. Anderson described a transepiphyseal technique for anatomic reconstruction of the ACL which avoids the distal femoral physis. We have shown that multiple structures are at risk with transphyseal drilling of the ACL femoral tunnel. The LCL is most at risk during guide pin placement for the AM bundle. Both the LCL and popliteus tendons are at risk during guide pin placement for the PL bundle. A transepiphyseal femoral tunnel is a promising option for anatomic reconstruction of the ACL in the skeletally immature patient. This technique avoids the distal femoral physis, thus decreasing the incidence of distal femoral growth arrest that can be seen following transphyseal reconstruction techniques. It also allows for anatomic placement of the ACL femoral tunnel. Several retrograde drilling devices are now available that allow for minimally invasive, inside-out placement of the ACL femoral tunnel. With retrograde devices a poke and spread technique should be utilized to reach the lateral femoral cortex, thus avoiding several important structures. Violation of the lateral cortex should also be avoided to preserve the lateral anatomic structures. Alternatively an outside in approach can be utilized. With the outside-in technique, we recommend a small incision to facilitate exposure and retraction of the important lateral structures. It is our hope that a better understanding of the lateral soft tissue anatomy will avoid injury to the vital lateral structures.

Reconstruction Technique Affects Femoral Tunnel Placement in ACL Reconstruction

Grafts placed too anteriorly on the femur are reportedly a common cause of failure in anterior cruciate ligament reconstruction. Some studies suggest more anatomic femoral tunnel placement improves kinematics. The ability of the transtibial technique and a tibial tunnel-independent technique (placed transfemorally outside-in) to place the guide pin near the center of the femoral attachment of the anterior cruciate ligament was compared in 12 cadavers. After arthroscopic placement of the guide pins, the femur was dissected and the three-dimensional geometry of the femur, anterior cruciate ligament footprint, and positions of each guide pin were measured. The transtibial guide-pin placement was 7.9 +/- 2.2 mm from the center of the footprint (near its anterior border), whereas the independent technique positioned the guide pin 1.9 +/- 1.0 mm from the center. The center of the footprint was within 2 mm of an anteroposterior line through the most posterior border of the femoral cartilage in the notch and a proximodistal line through the proximal margin of the cartilage at the capsular reflection. More accurate placement of the femoral tunnel might reduce the incidence of graft failure and might reduce long-term degeneration observed after reconstruction although both would require clinical confirmation.

Anatomical and Nonanatomical Double-Bundle Anterior Cruciate Ligament Reconstruction

Background Studies have suggested that double-bundle anterior cruciate ligament reconstruction may restore intact knee kinematics better than single-bundle anterior cruciate ligament reconstruction. Although the tunnel position of the femoral anteromedial bundle is well established, the effects of different posterolateral bundle positions on knee kinematics are unknown. Hypothesis Double-bundle anterior cruciate ligament reconstruction with an anatomical (shallow) femoral posterolateral bundle tunnel placement will restore knee kinematics more closely than will a nonanatomical (deep) femoral posterolateral bundle tunnel position. Study Design Controlled laboratory study. Methods In 12 human cadaveric knees, the kinematics of the intact knee, anterior cruciate ligament-deficient knee, and double-bundle anterior cruciate ligament-reconstructed knees with nonanatomical femoral posterolateral tunnel placement and anatomical posterolateral bundle placement were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation using a robotic/universal force moment sensor testing system. Statistical analyses were performed using a 2-way analysis of variance test. Results Double-bundle anterior cruciate ligament reconstruction with nonanatomical posterolateral bundle placement showed significantly higher anterior tibial translation under anterior tibial and combined rotatory load than did the intact knee at 0° and 30° of knee flexion (P < .05). Reconstruction with an anatomical posterolateral tunnel placement restored the intact knee kinematics and showed significantly lower anterior tibial translation under anterior tibial and combined rotatory load when compared with reconstruction with nonanatomical posterolateral placement (P < .05). Conclusion Double-bundle anterior cruciate ligament reconstruction using the anatomical posterolateral bundle tunnel position restores the intact knee kinematics. A nonanatomical posterolateral bundle position results in rotatory instability. Clinical Relevance Double-bundle anterior cruciate ligament reconstruction should be performed using anatomical tunnel placement of the anteromedial and posterolateral bundles. Nonanatomical double-bundle reconstruction may fail to show any clinical superiority to single-bundle reconstruction and should be avoided.

Graft Length Changes in the Bi-Socket Anterior Cruciate Ligament Reconstruction: Comparison Between Isometric and Anatomic Femoral Tunnel Placement

To compare the length change of grafts in bi-socket anterior cruciate ligament (ACL) reconstruction between isometric and anatomic placement. Case series. The subjects were 110 knees of 110 patients with a mean age of 27 years. All knees were reconstructed using multistranded autogenous semitendinosus tendon and the bi-socket procedure. Of those, 43 knees were reconstructed in the isometric position, around the isometric point (group I) and the remaining 67 in the anatomic position, mimicking the anatomic footprint of ACL (group II). Grouping was performed based on the femoral socket position. Each femoral socket for the anterior medial graft (AMG) and the posterolateral graft (PLG) for the left knee was positioned at 1 o'clock and 2 o'clock to 2:30 in group I, or 2 o'clock and 3 o'clock in group II in the posterior border of the notch. Their positioning for the right knee was at 11 o'clock and 9:30 to 10 o'clock in group I, or 10 o'clock and 9 o'clock in group II. The length changes of grafts were intraoperatively measured while extending the knee from 120 degrees to full extension, using a commercially available isometric positioner. The Student t test was used for statistical analysis. All the grafts showed the pattern of elongation approaching extension. The length change of AMG and PLG was 1.3+/-0.6 mm and 2.2+/-1.0 mm in the group I, 1.4+/-0.7 mm and 2.5+/-0.9 mm in the group II, respectively. There was no statistically significant difference in the values of AMG (P = .51) and PLG (P = .074) between the 2 groups. The length change of ACL grafts placed in the anatomic position was not significantly different from that positioned in the isometric position. Level IV, case series.

Knee Stability and Graft Function after Anterior Cruciate Ligament Reconstruction

Background Locations of femoral tunnels for anterior cruciate ligament replacement grafts remain a subject of debate. Hypothesis A lateral femoral tunnel placed at the insertion of the posterolateral bundle of the anterior cruciate ligament can restore knee function comparably to anatomical femoral tunnel placement. Study Design Controlled laboratory study. Methods Ten cadaveric knees were subjected to the following external loading conditions: (1) a 134-N anterior tibial load and (2) combined rotatory loads of 10-N.m valgus and 5-N.m internal tibial torques. Data on resulting knee kinematics and in situ force of the intact anterior cruciate ligament and anterior cruciate ligament graft were collected using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) anatomical double-bundle reconstructed, and (4) laterally placed single-bundle reconstructed knees. Results In response to anterior tibial load, anterior tibial translation and in situ force in the graft were not significantly different between the 2 reconstructions except at high knee flexion. For example, at 90° of knee flexion, anterior tibial translation was 6.1 ± 2.3 mm for anatomical double-bundle reconstruction and 7.6 ± 2.6 mm for laterally placed single-bundle reconstruction (P < .05). In response to rotatory loads, there were no significant differences between the 2 reconstruction procedures (4.8 ± 2.4 mm vs 4.8 ± 3.0 mm in anterior tibial translation at 15° of knee flexion, P > .05). Conclusion Lateral tunnel placement can restore rotatory and anterior knee stability similarly to an anatomical reconstruction when the knee is near extension. However, the same is not true when the knee is at high flexion angles. Clinical Relevance To reproduce the complex function of the anterior cruciate ligament, reproducing both bundles of the anterior cruciate ligament may be necessary.