Double-bundle ACL reconstruction restores anatomy, kinematics

Anatomic double-bundle reconstruction is a concept, not just a technique.

Issue: September 2007

ByFreddie H. Fu, MD, DSc(Hon), DPs(Hon)

ByAnil Ranawat, MD

Despite significant advancements in ACL surgery, meta-analysis studies have demonstrated significant problems after single-bundle reconstructions: 10% to 30% of patients complain of persistent instability (Freedman et al. 2003) and approximately 40% of the patients never make a full functional recovery after surgery (Biau et al, 2007). A prospective midterm study has also shown that 90% of patients have degenerative radiographic changes (Fithian et al, 2005). Therefore, even though ACL surgery has been thought of by many as a clinical success, there is still much room for improvement.

Anatomy

Anatomic and biomechanical studies reveal that the ACL has two functional bundles, the anteromedial (AM) bundle and the posterolateral (PL) bundle. (Chhabra et al, 2006). Anatomical analysis of the ACL in fetal, arthroscopic and cadaveric studies demonstrates that there are the two distinct functional bundles with unique insertion sites (Figure 1), (Chhabra et al, 2006; Ferretti et al, 2007). In addition, the AM and PL bundles differ in their length, width, and insertion area (Zantop et al, 2006).

The ACL’s double-bundle anatomy has distinct insertion sites on both the tibial and femoral side. Each bundle is named after its tibial insertion site, with the AM bundle being more anterior and medial, and the PL bundle is posterior and lateral. Unlike the tibial insertion sites, the orientation of the femoral insertion sites varies with knee flexion. In full extension, the bundles are oriented vertically but become more horizontal as the knee approaches 90· of flexion, with the PL insertion site lying more distal relative to the AM. As a result, the AM and PL bundles change from being parallel in extension to crossing in flexion.

Recently, we have found two osseous landmarks: the lateral intercondylar ridge and the lateral bifurcate ridge (Figure 2). When the knee is in 90· of flexion, the lateral intercondylar ridge runs through the entire ACL footprint with no ACL fibers attaching superior to this ridge. The lateral bifurcate ridge runs almost perpendicular to the lateral intercondylar ridge and separates the AM and PL bundle femoral insertion sites. These landmarks can be used as intraoperative guides in locating the femoral insertion sites of the AM and PL bundles and thus ensure anatomic tunnel placement.

Figure 1: Arthroscopic image
Arthroscopic image demonstrating two distinct functional bundles with unique insertion sites. AM = anteromedial bundle, PL = posterolateral bundle, LFC = lateral femoral condyle.

Figure 2:Two osseous landmarks
This image shows the two osseous landmarks: the lateral intercondylar ridge and the lateral bifurcate ridge.

Images: Fu FH

Basic science

Biomechanical studies suggest that each bundle makes a unique kinematic contribution to knee function with the AM bundle being the major anterior-posterior restrictor and the PL bundle being the main of rotational stabilizer (Zantop et al, 2007). An in vivo kinematic study showed that conventional single-bundle ACL reconstruction, which mostly mimics an AM bundle reconstruction, may successfully restore anterior-posterior knee stability but does not successfully restore rotational stability (Tashman et al, 2004). In addition, cadaveric biomechanical studies have shown that double-bundle ACL reconstructions more closely restore knee kinematics than single-bundle ACL reconstructions (Yagi et al, 2002).

Restoring anatomy

The fundamental principle in anatomic double-bundle ACL reconstructive surgery is restoration of native anatomy. This is achieved by restoring the two-bundle anatomy of ACL, as well as reproducing the insertion sites and tension pattern of each bundle (Fu et al, 2007). To perform this “insertion site surgery,” the native insertion sites of each bundle are identified and marked on the tibial and femoral side. The tunnels are then drilled at the native insertion sites (Figure 3). The AM and PL grafts are passed (Figure 4) and tensioned at 60º and 0· of flexion respectively to restore the native tension pattern of each bundle (Gabriel et al, 2004).

The most critical technical pearl in performing anatomic double-bundle reconstruction is accurate portal placement using a three portal technique (Cohen et al, 2007). Using this technique, we visualize the femoral insertion site from a central medial portal and the tibial insertion site from a high lateral portal. This gives us a superior view of both insertion sites. With regard to the femoral insertion site, a medial portal view obviates the need for a notchplasty, which is rarely performed since it destroys the native soft tissue and osseous anatomy of the lateral femoral condyle, leaving no references points for tunnel placement. If a notchplasty is necessary, it is only performed after marking the native insertion sites and drilling the femoral tunnels.

Recent prospective and randomized level I and level II studies have reported favorable clinical outcomes after double-bundle ACL reconstructions (Yasuda et al, 2006; Aglietti et al, 2007; Jarvela 2007; Muneta et al, 2007; Yagi et al, 2007). At the University of Pittsburgh, the double-bundle reconstruction patients have better range of motion at the first 3 months postoperative period than single-bundle reconstruction patients while maintaining ligamentous stability (Fu et al, 2007).

A “concept,” not a technique

Anatomic double-bundle reconstruction is a concept, rather than just a technique. It can be applied to single-bundle reconstruction, one-bundle augmentation, and revision ACL surgery in order to more closely restore the native anatomy of ACL. This concept is not only versatile, but also individualized to each patient. Since every knee is unique with regards to both condylar size and insertion site anatomy, treatment is tailored to the patient’s specific anatomy. Research has shown that there is tremendous variability in ACL anatomy, but that double-bundle anatomy is highly consistent. One could say that you are born with, live with and die with a double-bundle ACL.

We should keep in mind that reduction, not fixation, is the very basis of orthopedics. Too often, ACL surgery focuses on fixation and graft selection, when in fact the goal of all ACL surgery, and anatomic double-bundle reconstruction in particular, should be to properly reduce the injury by restoring native anatomy. After 3 decades of arthroscopic ACL surgery, it is time for us to revisit the anatomy of ACL and try to restore it. As Jack Hughston said, “Pay particular attention to anatomy, because orthopedics is all anatomy, plus a little bit of common sense.”

Figure 3: Insertion site surgery
To perform an “insertion site surgery,” the native insertion sites of each bundle are identified and marked. The tunnels are then drilled at the native insertion sites.

Figure 4: Anteromedial and posterolateral grafts
The anteromedial and posterolateral grafts are passed through the tunnels.

For more information:
Freddie H. Fu, MD, DSc(Hon), DPs(Hon), can be reached at the University of Pittsburgh, Department of Orthopedic Surgery, 3471 Fifth Ave., Suite 1011, Pittsburgh, PA 15213; 412-687-3900; e-mail: ffu@msx.upmc.edu. He has no direct financial interest in any products or companies mentioned. Anil Ranawat, MD, can be reached at Sports Performance Center, 3200 South Water St., Pittsburgh, PA 15203; 412-432-3600. He has no direct financial interest in any products or companies mentioned.

References:

Aglietti P, Giron F, Cuomo P, Losco M, et al. Single-and double-incision double-bundle ACL reconstruction. Clin Orthop and Relat Res. 2007;454:108-113.
Biau DJ, Tournoux C, Schranz P, Nizard R. ACL reconstruction: a meta-analysis of functional scores. Clin Orthop and Relat Res. 2007;458:180-187.
Buoncristiani AM, Fotios P Tjoumakaris, Fu FH, Shen W, et al. Primary anatomic double bundle ACL reconstruction: A 2-year prospective cohort study. Presented at the American Orthopaedic Society for Sports Medicine Specialty Day Meeting. February 17, 2007. San Diego.
Chhabra A, Starman JS, Ferretti M, Vidal AF, et al. Anatomic, radiographic, biomechanical, and kinematic evaluation of the anterior cruciate ligament and its two functional bundles. J Bone Joint Surg AM. 2006;Suppl.4:2-10.
Cohen SB, Fu FH. Three-portal technique for anterior cruciate ligament reconstruction: use of a central medial portal. Arthroscopy. 23(3):325.e1-5.
Ferretti M, Levicoff EA, Macpherson TA, Moreland MS, et al. The fetal anterior cruciate ligament: an anatomic and histologic study. Arthroscopy. 2007;23(3):278-283.
Fithian DC, Paxton EW, Stone ML, Luetzow WF, et al. Prospective trial of a treatment algorithm for the management of the anterior cruciate ligament. Am J Sports Med. 2005;33(3):335-346.
Fu FH, Shen W, Honkamp N, Baer GS, et al. Double-bundle ACL reconstruction. AAOS Orthopaedic Knowledge Online. 2007; http://www5.aaos.org/oko/description.cfm?topic=SPO016&referringPage=http://www5.aaos.org/oko/menus/sports.cfm.
Gabriel MT, Wong EK, Woo SL, Yagi M, et al. Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads. J Orthop Res. 2004;22(1):85-89.
Järvelä T. Double-bundle versus single-bundle anterior cruciate ligament reconstruction: a prospective, randomize clinical study. Knee Surg Sports Traumatol Arthroscop. 2007;15(5):500-507. Epub.
Muneta T, Koga H, Mochizuki T, Ju YJ, Hara K, et al. A prospective randomized study of 4-strand semitendinosus tendon anterior cruciate ligament reconstruction comparing single-bundle and double-bundle techniques. Arthroscopy. 2007;23(6):618-628.
Tashman S, Collon D, Anderson K, Kolowich P, et al. Abnormal rotational knee motion during running after anterior cruciate ligament reconstruction. Am J Sports Med. 2004;32(4):975-983.
Yagi M, Kuroda R, Nagamune K, Yoshiya S, et al. Double-bundle ACL reconstruction can improve rotational stability. Clin Orthop Relat Res. 2007;454:100-107.
Yagi M, Wong EK, Kanamori A, Debski RE, et al. Biomechanical analysis of an anatomic anterior cruciate ligament reconstruction. Am J Sports Med. 2003;30(5):660-666.
Yasuda K, Kondo E, Ichiyama H, Tanabe Y, et al. Clinical evaluation of anatomic double-bundle anterior cruciate ligament reconstruction procedure using hamstring tendon grafts: comparisons among 3 different procedures. Arthroscopy. 2006;22(3):240-251.
Zantop T, Herbort M, Raschke MJ, Fu FH,, et al. The role of the anteromedial and posterolateral bundles of the anterior cruciate ligament in anterior tibial translation and internal rotation. Am J Sports Med. 2007;35(2):223-227. Epub.
Zantop T, Petersen W, Sekiya JK, Musahl V, et al. Anterior cruciate ligament anatomy and function relating to anatomical reconstruction. Knee Surg Sports Traumatol Arthroscop. 2006;14(10):982-992. Epub.