Double-bundle versus single-bundle ACL reconstruction.(anterior cruciate ligament)(Report)

In the past decade, estimates quote the annual incidence of anterior cruciate ligament (ACL) injury as nearly 1 in every 3000 people in the United States. (1) As a result, over 100,000 ACL reconstruction procedures are performed each year. (2,3) Published outcomes, both short- and mid-term, have been favorable with regard to postoperative stability, functional scores, and return to activity. These same results, however, have revealed a subset of 10% to 30% of patients who do not have such favorable outcomes. Objective outcome measures, such as anteroposterior laxity, pivot shift, and Lysholm knee scores, have demonstrated that a subpopulation of patients have residual laxity or functional deficits that prevent a return to previous levels of activity and function. (4-10)

The published incidence of arthrosis following ACL reconstruction also has been less than encouraging. Several investigators have reported results that demonstrate arthritic changes in athletes despite reconstruction of the ACL following knee injury. (11-14) This progression is reported even more commonly if the ACL injury is associated with a medial meniscal tear. (15) Some investigators have suggested that the rate of arthritis progression after ACL injury and reconstruction is equal to or worse than would have occurred after nonoperative treatment. (16) With these studies reporting a subset of patents with poorer outcomes, the question that begs to be answered is whether the current practices of ACL reconstruction are adequately anatomic, and, if not, what techniques may need to be developed for improvement? This, in part, has been the driving force behind the increased interest in performing double-bundle ACL reconstructions and will be the focus of this review.

Anatomy of the ACL

Although the ACL has been recognized as a structure for thousands of years, a description of two distinct ACL bundles did not appear in the literature until 1975 and, consequently, is generally credited to Girgis and colleagues. (17) They named the two bundles anteromedial (AM) and posterolateral (PL), based on the insertion of the two bundles on the proximal tibia. Ferretti and coworkers (18) reference a paper published, in 1979, by Norwood and Cross, who also described the ACL, but as a three-bundle structure. Since these early descriptions, numerous articles have described a variable number of fascicles and grouped bundles comprising the ACL. Anatomic studies from fetal specimens support a distinct double-bundle composition of the ACL during fetal development. (18) Although as many as four bundles have been described, the consensus is that the ACL functions as a combination of two bundles, as first described by Girgis and associates (17) (Fig. 1). The AM bundle originates more superiorly and anteriorly on the lateral femoral condyle, is taut in flexion, and more relaxed in extension. The PL bundle originates more inferiorly and posteriorly and tightens in extension. Although named for the tibial insertion site, it is the location of the origins that determines the role of the bundles through the range of knee motion. Proponents of double-bundle reconstruction use these anatomically described groupings of fascicles as support for the rationale of double-bundle reconstruction (Fig. 2).

[FIGURE 1 OMITTED]

History of Double-Bundle Reconstruction

The earliest published discussions of double-bundle ACL reconstruction are from the 1980s.19,20 However, by the time Mott (19) published his surgical technique of a "double-bundle" reconstruction, in 1983, he had been using the technique for 5 years. As this was a surgical technique only, he did not include follow-up, treatment group descriptions, or outcome measures. His reconstruction described using a semitendinosus autograft through two tunnels in both the femur and tibia. Soon after, Zaricznyj (20) published a similar technique, using two tibial tunnels and one femoral tunnel. He followed 14 patients for 2 years and noted that 12 of the 14 patients scored good-excellent by the Hospital for Special Surgery (HSS) knee score. Zaricznyj also noted that none of the patients had a pivot shift following reconstruction, but three knees had a 1+ anterior drawer test. No mention was made of whether these patients were able to resume their previous activity levels or their previous occupations. (20)

[FIGURE 2 OMITTED]

Several years after these published techniques, Radford and Amis (21) reported their biomechanical assessment of double- versus single-bundle reconstruction. In this study, the investigators tested the flexion stability of six ACL intact cadaveric knees at both 20[degrees] and 90[degrees]. The native ACL was then removed, and testing was repeated with an over-the-top reconstruction method simulating the AM bundle, and then a trans-lateral femoral-condyle reconstruction simulating the PM bundle. A double-bundle construct was also simulated by the combination of the two. Of note, the reconstructed bundles were synthetic, created with polyester tape instead of biological components. The grafts were tensioned according to the investigators' estimation of the laxity of the native ACL before sectioning. They reported that the AM bundle simulation stabilized best at 90[degrees] of flexion, and the PM bundle simulation stabilized best at 20[degrees] of flexion. The addition of both bundles replicated the stability of the native knee before disruption of the native ACL. They concluded that double-bundle reconstruction most closely reproduced the stability of a native knee. (21)

Interestingly, the same group published an animal model study 4 years later, looking again at single- versus double-bundle reconstruction. Using three groups of eight sheep each, the native ACL was …