The Double Bundle Bungle

Try saying “The Double-Bundle Bungle” three times quickly in a row—it can actually be a little tricky. It’s a tongue-twisting rhyme. Or maybe it sounds a little like a cookie advertisement. But either way, the title is not without purpose. Aside from rhyming it actually presents an issue yet to be resolved by clinical tests. Is there truly a benefit to the double-bundle anterior cruciate ligament (ACL) procedure? Or is the procedure in fact a bungle, inadequate in comparison to the ACL procedure most commonly used?

Each year over 100,000 surgeries take place to reconstruct the ACL of the knee. The ACL initially comes stocked with two ligament bundles, the anteromedial and the posterolateral. In a typical reconstructive surgery both of these bundles are replaced using the single-bundle method, which replaces just one of the torn ligament bundles with either a hamstring tendon or a patellar tendon. The double-bundle method seeks to improve this reconstruction process by replacing both bundles. The primary goal of improving the reconstruction process is better restoration of the patient’s range of motion within the knee and improved restoration of knee stability.

As a new procedure here in the U.S., the double-bundle ACL reconstruction has its supporters and skeptics. The key question becomes, is there added value to the patient when such a procedure is performed in preference to the single-bundle procedure? Does the double-bundle ALC reconstruction really improve the life of the patient more than any other option? In theory the answer is a resounding yes. Who wouldn’t want a greater range of motion or better knee stability? The very idea of this procedure providing results closer to the natural state of the knee is appealing.

Yet the operative wording is “in theory.” In practice the double-bundle procedure is not without its drawbacks. The initial roadblock is that as a procedure new to the United States, very few surgeons are trained on the procedure and even fewer are experienced at it. Conversely, the single-bundle procedure has been the standard for years and complications remain exceptionally low.

This low rate can be illustrated using a sample from the PearlDiver database, which in total contains records for more than 6 million patients from 2004–2006. Of these patients, a sample of 35,122 underwent ACL reconstruction, and only 20 from the sample set had complications through the use of the single-bundle method, as shown in Table 1 below.

Table 1: Complications During ACL Reconstruction, Single-Bundle

While numbers for the double-bundle procedure are still unavailable, they are likely to be in contrast to those for the common single-bundle procedure. Aside from the lack of surgeons trained in the double-bundle procedure, the procedure itself is more complicated and more time-consuming than the single-bundle reconstruction, increasing the odds of complications. With the double-bundle procedure there are two tunnels to be drilled instead of one, and this has yet to become an exact science. Also, there are two bundles to be grafted, doubling the amount of work needed in an already traumatized knee.

While there are a number of roadblocks ahead for the new procedure, one area of concern was presented in May 2007 at the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. In a study of 52 patients undergoing ACL reconstruction using the double-bundle procedure, 11 patients contracted deep vein thrombosis (DVT). That is over 21%! 

So the question must then be asked, what is the normal incidence of deep vein thrombosis  following ACL reconstruction using the single-bundle method? Again using our original sample of 35,122 patients from the PearlDiver database, we found that there is a significant difference in the frequency of DVT diagnoses among the double-bundle and single-bundle patients. As shown below in Table 2, within our  sample of single-bundle patients, only 38 were diagnosed with DVT.

Table 2: Incidents of Deep Vein Thrombosis (DVT)

Clearly there is a huge difference in DVT incidence from the single-bundle method to the double-bundle method, part of which may be attributed to the method of the 52-patient double-bundle study. During the study, surgeons did not use pharmacological DVT prophylaxis in the patients, which is normal protocol in single-bundle procedures. While we can assume that the lack of DVT prophylaxis would account for a significant difference, it is very difficult to say that this dissimilar protocol alone would account for a change from 0.11% to over 21%.

Moving back toward our primary question of adding value to the patient, is this increased risk of DVT offset by the value of the additional benefits the procedure provides? A greater range of motion and knee stability may still sound positive. Taking the question one step further, how do we measure that value against the possibility of complications from the surgery?

One simple method is to consider the best-case scenario of outcomes for both procedures. The double-bundle procedure, by design, can restore the patient’s knee to a range of motion closer to that of the original internal knee makeup before the ACL damage.

However, it must be considered that the best-case scenario for the single-bundle method might not be too far behind the best-case scenario for the double-bundle method. In some cases the single-bundle procedure might even be seen as superior because of the decreased potential for surgical complications. Consider that numerous players in the National Football League have torn their ACL and yet been able to return to the game within one to two seasons. Players such as Edgerrin James and Terrell Davis have been considered great even after their return from single-bundle ACL reconstructive surgery.

With that in mind, while many of the injuries suffered to the ACL are sports-related, few patients are professional football players. Most ACL patients are able to move on to a perfectly normal life. But the mere fact that an athlete patient can return to a professional sport after a single-bundle reconstruction procedure leads to the conclusion that the potential success rate for the single-bundle method is already very high. If a player can continue playing professional football, and do so successfully, how much more does the double-bundle procedure really offer to the patient above the accomplishments of the single-bundle procedure?

From the research to date and the theory behind the double-bundle ACL reconstruction, the answer is that it depends. From an athlete standpoint, the chances are good that he will not be as good as he once was. A study done by the National Football League showed 20% of players did not return after an ACL reconstruction. Of those players who do return, various analyses have demonstrated that 60%–90% have a statistically decreased level of performance from levels prior to injury. So it may be that the double-bundle method will be able to improve the outcomes for some professional athletes.

But these statistics demonstrate only that there is some room for improvement, and it is at the professional athletic level. The bar has been set extremely high for the double-bundle procedure. With much clinical testing yet to be done, it is possible the double-bundle method could become a common procedure and someday may even succeed the status quo single-bundle method. Yet to most common everyday patients, even with the potential of the procedure, the double-bundle method will not offer the added value necessary to select the double-bundle over the single-bundle method anytime soon.