Posterior Proximal Cartilage of the Lateral Femoral Condyle as a Reference for Positioning the Femoral Tunnel in ACL Reconstruction

Abstract

Background:

Due to the similarity among specimens in the height of the anterior cruciate ligament (ACL) on the distal proximal axis in relation to the proximal posterior cartilage of the lateral femoral condyle (point C), it is known this point can be used as an arthroscopic intraoperative parameter to define the position of the femoral tunnel in ACL reconstruction.

Indications:

For ACL reconstruction, point C can be used as an arthroscopic intraoperative parameter to define the position of the femoral tunnel on the distal proximal and anteroposterior axes.

Technique Description:

For access to the joint, standard arthroscopic ports, both anterolateral (AL) and anteromedial (AM), are used. By directing the camera toward the posterior region of the lateral femoral condyle through the AM port, it is possible to visualize the end of the posterior and proximal articular cartilage, the so-called C point. In this case, we sought to position the center of the femoral tunnel in the center of the AM band of the ACL. Holding the camera through the AM portal and visualizing point C, a millimeter-scale femoral guide is introduced through the AL portal toward the posterior femoral cartilage (point C) and positioned over it, creating a line between point C and the lateral distal femoral cartilage. The distance between point C and the distal femoral cartilage is measured. At this time, an accessory AM portal 1.5 cm from the AM port is constructed. Through it, with the aid of an ice pick or radiofrequency tip, a marking is made in the deep to shallow axis at 35% of this distance. Then, approximately 2 mm above the imaginary line formed by the union of point C and the lateral distal femoral cartilage, the center of the femoral tunnel is marked.

Results:

Point C is an anatomical landmark that is easy to view and is present in all knees; thus, it can be used as a reference during surgery for positioning the femoral tunnel.

Discussion/Conclusion:

Point C can be used as an arthroscopic intraoperative parameter to define the position of the femoral tunnel in ACL reconstruction.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Greetings, everyone. In this video, we will present the proximal posterior cartilage of the lateral femoral condyle as an arthroscopic reference for anterior cruciate ligament (ACL) reconstruction.

There are no conflicts of interest for this presentation.

The anatomy of the ACL has been studied for over 1 century. The first publication regarding ACL surgery was in 1903 about ligament repair. Since then, much has been studied and published about the ACL and many aspects are still being discussed nowadays. For example, the presence or absence of 2 different bundles, the ribbon-like appearance of the 2 bundles, ¹⁰ the presence of direct and indirect fibers in the femoral and tibial insertions, and the different functions of the bundles during flexion and extension of the knee. ⁶

Due to the anatomical and functional controversies related to the ACL, there are also controversies regarding where the center of the femoral tunnel should be positioned for single- or double-bundle reconstruction. ⁸ Some recent studies have indicated that reconstruction with the tunnel in the center of the anteromedial (AM) bundle is ideal, ² but many surgeons prefer the central position (in the middle of the native ACL), while others argue for intermediate positioning between the center of the ACL and the center of the AM bundle.^4,7

Another difficulty is to determine during the surgical procedure the exact location of these points (the center of the ACL and the center of the two bundles). Some parameters can be used to help the surgeon determine these points, such as arthroscopic visual parameters (e.g., the lateral femoral intercondylar crest, bifurcated wall, distal joint margin, posterior intercondylar sulcus, and anterior horn of the lateral meniscus) ⁹ or radiographic parameters, such as the quadrants of Bernard et al. ¹ Another little-used parameter is the relationship between the posterior proximal cartilage of the lateral femoral condyle and the ACL in both the high low and shallow deep planes. ⁵ An anatomical study published in 2022 ³ concluded that due to the similarity among specimens in the height of the ACL on the shallow deep axis in relation to the proximal posterior cartilage of the lateral femoral condyle (point C), this point can be used as an arthroscopic intraoperative parameter to define the position of the femoral tunnel in ACL reconstruction. Point C can also be used on the high low axis but with greater caution and the additional use of secondary parameters because of the anatomical variation observed between the cases studied.

In these images, we observe point the C during an arthroscopic procedue. This point is easily identified after cleaning the femoral remnant of the ACL.

The case presented in the video is a 28-year-old male soccer player who suffered a knee sprain 2 months before surgery, evolving to knee instability. On physical examination, the patient had a normal axis and complete mobility, presenting with a positive Lachman test, a positive anterior drawer test and a postive grade 1 pivot shift test. The posterior drawer test was negative as were the tests for posteromedial and posterolateral instabilities. Magnetic resonance imaging showed a complete proximal ACL lesion without meniscal or chondral changes.

The anterolateral (AL) and AM portals are created in a standard manner. An AM accessory portal is also performed. The arthroscopic procedure begins with articular inspection, checking for meniscal and chondral lesions. The torn ACL fibers are then removed from the femur, allowing a clear outlook of the medial aspect of the lateral femoral condyle.

At this point, the arthroscope is shifted to the AM portal, allowing a more direct visualization of the ACL femoral insertion and also the proximal posterior cartilage of the lateral femoral condyle. Through the AL portal, a femoral guide is positioned at the point C, and the distance between the point C and the distal cartilage of the lateral femoral condyle is measured—in this case, 24 mm. The goal is to create the AM bundle femoral insertion at a point located at 35% of the measured distance—in this case, 8 mm.

Through the AM accessory portal an ice pick or radiofrequency device is introduced, and a mark is performed at this point. Then, the femoral guide tip is positioned approximately 2 mm above this mark, at 35% of the measured distance, and the guidewire is introduced from outside of the lateral aspect of the joints. Viewing from the AM portal, the broke tip shows the center of the AM bundle, the center of the ACL, and the center of the posterolateral bundle, and their relation with the posterior femoral cartilage.

The AM tunnel is then drilled from the outside in through a small lateral incision. Looking at the femoral condyle from the AM portal, it is possible to observe the adequate position of the tunnel created at the AM bundle insertion. Next, the tibial tunnel is created in the standard manner using the appropriate guides at the center of the ACL stump. Using a suture passer through the tunnels, the graft is routed from the tibia to the femur. Lastly, the graft fixation is performed—first, at the femur with an interference screw introduced from outside in, and then, with the knee at full extension and neutral rotation, the graft is fixed under manual tension in the same manner.

Thank you for watching.