Single-tunnel reconstruction is more than adequate

A second tunnel does not eliminate pivot shift in 15%-25% of double-bundle cases.

Issue: March 2008

ByStephen M. Howell, MD

Stephen M. Howell, MD
Stephen M. Howell

It is true that two capable people can look at the same problem and see different solutions. Indeed, my good friend Dr. Freddie Fu has done a lot for ACL reconstruction over the last 4 or 5 years, especially bringing us the double-tunnel concept and the importance of where we place our tunnels, and we are grateful for his contribution. However, I think the literature supports that one tunnel is more than adequate for the reconstruction.

Another option, and perhaps a better way to reduce rotatory stability is to do an anatomic single-tunnel reconstruction, but you must avoid PCL impingement. In order to do that, the single femoral tunnel has to be centered halfway between the apex and base of the notch where the bone bridge lies for the double-tunnel reconstruction. When the single tunnel is in this location, there is little room for a second tunnel, unless the AM (anteromedial) femoral tunnel is placed too vertical.

The addition of a second tunnel often fills the notch with too much collagen; resulting in roof impingement as well as PCL impingement with stiffness, loss of motion, and instability if motion is regained.

If the second tunnel is so effective, then why do studies that report their two-tunnel results still have a pivot shift in 15%-25% of the knees? Might not the answer be better placement of the single tunnel, since the success of single tunnel is quite good?

PCL impingement

There is absolutely no agreement between experts on where to put the two tunnels. And if you look at where the better results are with the two-tunnel reconstruction, they are generally compared to a one-tunnel reconstruction where the AM femoral tunnel is up at the apex of the roof with PCL impingement and not to an anatomically placed single-tunnel reconstruction without PCL impingement. This is the justification for adding the second tunnel, because you have room to put in a second tunnel; however the surgeon hasn’t recognized that the single tunnel has been in the wrong place all along and the pivot shift is due to the graft stretching from PCL impingement.

The complications of PCL impingement include: the patient struggles to get their flexion back at 4 weeks; they’re shy 15°-20° of flexion with an effusion in the knee; and at 2 months, they’re shy 10° with a persistent effusion. Between 2 and 6 months the patient may regain full flexion, but his anterior laxity increases as measured by the KT-1000, a Lachman Test still has a good endpoint but it’s a +1, and he pivots. If you eliminate PCL impingement, you will see better flexion, better stability and less effusions.

We like to put our tunnels a little further down the side wall, so it creates a triangular space between the PCL and the ACL graft. We put our graft where the bone bridge is in the double-tunnel reconstruction. This gives an anatomic single-tunnel reconstruction in which the tension pattern is normal with reciprocal tensile behavior like the intact ACL.

Radiographically, what are we looking for? You should keep the angle of the tibial tunnel with respect to the medial joint line less than 70°, in the 60°-65° range, and the lateral edge of the tibial tunnel should pass through the tip of the lateral tibial spine. This gets your femoral tunnel further down the sidewall and away from the apex of the notch when you drill the femoral tunnel through the tibial tunnel.

If you look at Kondo’s article, he showed that the quality of that PL (posterolateral) bundle either failed or was very poor in 7%-24% of their double-bundle reconstructions. The cause might be too medial placement of the tibial tunnel. Medial placement of the tibial tunnel would cause the graft to stretch around the PCL.

Pivot shift

Why do 15%-25% of the double- bundle ACL reconstructions still have a pivot shift in recent studies? A prominent European surgeon published in 2006 that 16% had a pivot shift. A prominent Asian surgeon published in 2006 that he had a 22% pivot shift, and another published in 2007 noted a positive pivot shift in 15%.

My review of arthroscopic photos or schematic drawings in these studies showed too vertical placement of the AM femoral tunnel and too medial placement of the tibial tunnel. An arthroscopic clue that the graft is properly placed is when you see that the femoral tunnel is half-way down the sidewall, the tibial tunnel is not medial to the PCL, and there is a triangular space between the PCL and ACL graft. A radiographic clue: If you drill the femoral tunnel through the tibial tunnel, you will see the lateral edge of the tibial tunnel passing through the tip of the lateral tibial spine as an angle of 60°-65° with respect to the medial joint line of the tibia. If we look at our clinical data from the United States, I couldn’t find any clinical publications as of 2007 that have reported the incidence of pivot shift in our double- bundle reconstructions.

Suboptimal placement

Radiographically, there’s no agreement among experts on where to put the tunnel. One surgeon’s PL tunnel can be another surgeon’s AM tunnel. I think that generally one of the two tunnels in a double-bundle reconstruction is suboptimally placed. The AM femoral tunnel is too vertical, and the PL tunnel is too far down the sidewall. We really don’t know what the tension is in these bundles because kinematic cadaveric studies have only taken the knee to 90° of flexion, which misses what is happening from 90° to 140° of flexion, the range where graft tension rises from PCL impingement. Toritsuka supports the view that the AM tunnel should not be too vertical as he found better rotatory control when he moved both tunnels further down the side wall away from the PCL.

Extension loss

An alarming finding in Asagumo’s article on double-bundle reconstruction published in 2007 is the extension loss in 26% of their knees with two tunnels. Extension loss from roof impingement threatens a revisit to the same problem that plagued us in the late 80s and early 90s. I attribute their extension loss to moving the AM tibial tunnel anterior to make room for the PL tibial tunnel, and to overstuffing the notch trying to get too much collagen in a confined space. This can cause you to end up with extension loss, or the roof fractures some of the graft, resulting in instability and ultimately a revision. Because of the loss of extension in the double-tunnel group and no difference in measured stability and subjective results, these authors did not advocate double-tunnel reconstruction. Ochi in 2004, and Hamada in 2001 had the same findings that double tunnel has no advantage.

So when these results are reported with double-tunnel vs. single-tunnel reconstruction, we need to look beyond rotatory stability as the ultimate determinant. We need to look back and ask, “Are the double tunnels having extension problems? Are they having flexion problems? Are they having prolonged effusions? And, is their rehabilitation more arduous?” Remember, patients are not looking for you to restore stability and make a stiff, swollen knee; they want to have a rapid uneventful recovery where they can do the rehabilitation easily and get a predictable result.

Two-tunnel tips

If you want to do two-tunnel reconstruction, be careful. Be careful not to make the AM femoral tunnel too vertical and the tibial tunnel not too medial because you will lose at least the medial half of the graft, and it’s going to stretch out or limit flexion as you try to regain flexion. Be careful not to make the AM tibial tunnel too anterior or the graft will impinge on the roof, and it’s either going to stretch out or limit extension as you try to regain extension.

If you want to do single two tunnel, think about centering the femoral tunnel 50% down the sidewall of the arc of the notch; that way you will get it away from the PCL. Remember you will almost always have to widen the notch to do so and the lateral edge of the tibial tunnel should pass through the lateral tibial spine at an angle of 60°-65° with respect to the medial joint line of the tibia.

With either technique, make it a habit to arthroscopically check for the “triangle.” Look for the space between the lateral edge of the PCL and your graft. It’s a good visual cue that you have avoided PCL impingement.

If your vacillating between the single- and double-tunnel techniques make sure that you weigh the longer surgical time, the impingement and motion issues, the 15%-25% incidence of pivot shift, the difficulty in picking those tunnel locations off distorted footprints, and the more difficult two-stage revisions. If you are having trouble with rotatory stability, might I suggest you first try to refine your single-tunnel technique and eliminate PCL impingement before going to two tunnel.

Finally, there is good evidence that the second tunnel is not the solution. If that were the case then why have we had pretty good results with the one-tunnel reconstruction? If the second tunnel was a prominent determinant of the outcome, then we should have seen that the one tunnel stabilized the knee only 20%-30% of the time and that the second tunnel stabilizes the knee 95%-100% of the time. This is not our experience. The key to sorting out whether one technique is superior to the other is multicenter prospective randomized trials, in large numbers of subjects, comparing double-tunnel to an anatomic single-tunnel reconstruction without PCL impingement, instead of comparing a double-tunnel to a non-anatomic single-tunnel with PCL impingement.

For more information:

Steven M. Howell, MD, can be reached at 810 Timberlake Way, Suite F, Sacramento, CA 95823-5409; 916-689-7370; e-mail: sebhowell@mac.com.

References:

Asagumo H, Kimura M, Kobayashi Y, et al. Anatomic reconstruction of the anterior cruciate ligament using double-bundle hamstring tendons: surgical techniques, clinical outcomes, and complications. Arthroscopy. 2007;23(9):1027; author reply 1027-1028.

Howell SM. One Tunnel is enough in ACL reconstruction. Presented at Orthopedics Today Hawaii 2008. January 13-16. Lahaina, Maui, Hawaii.