Journal Club - ACL Reconstruction and the Lateral Extra-articular Tenodesis (LET)

Journal Club is a recurring series where we look at recent research in orthopedic sports medicine and talk through what it may mean for our patients.

Title

Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial

Authors

Alan M.J. Getgood, MD; Dianne M. Bryant, PhD; Robert Litchfield, MD; Mark Heard, MD; Robert G. McCormack, MD; Alex Rezansoff, MD; Devin Peterson, MD; Davide Bardana, MD; Peter B. MacDonald, MD; Peter C.M. Verdonk, MD, PhD; Tim Spalding, FRCS; and the STABILITY Study Group

Journal

The American Journal of Sports Medicine. 2020;48(2):285-297.

Study design

Multicenter randomized clinical trial. Level of evidence, 1.

First, a little background:

When most people picture an ACL reconstruction, they picture the new ligament being placed inside the knee, in roughly the same position as the ligament that tore. That is exactly what it is, and for most patients it works beautifully.

But a subset of knees stay a little loose afterward. Not loose in the front-to-back direction, which the graft controls well, but loose in rotation. Surgeons measure this with an exam called the pivot shift, where the shin bone slides and then clunks back into place as the knee is bent. Patients usually describe it differently. They say the knee feels like it might give out when they plant and cut, even though everything looks fine on paper.

That leftover rotational looseness matters. It has been linked to lower satisfaction, more trouble getting back to sport, and a higher chance of the graft tearing again.

So what is a lateral extra-articular tenodesis?

A lateral extra-articular tenodesis, usually shortened to LET, is a small additional procedure done on the outside of the knee at the same time as the ACL reconstruction.

The surgeon takes a narrow strip of the iliotibial band, which is the thick band of tissue running down the outside of the thigh, and leaves it attached at its lower end. That strip is passed underneath the lateral collateral ligament and secured to the femur just above the joint. The result is a checkrein on the outside of the knee that resists the rotation the ACL graft alone does not fully control.

Two things are worth knowing about it. It is not a replacement for the ACL graft, it is an addition to it. And it is not new. Versions of this operation were common in the 1970s and 1980s, fell out of favor as arthroscopic reconstruction improved, and have returned over the last decade as our understanding of the structures on the outside of the knee has gotten better.

What the study looked at

The STABILITY I trial asked a straightforward question.

In young patients at high risk of failure, does adding a LET to a standard hamstring ACL reconstruction lower the chance that the reconstruction fails?

Patients were eligible if they were 25 or younger and met at least two of three criteria: a high-grade pivot shift on exam, a plan to return to a high-risk pivoting sport, or generalized ligamentous laxity, meaning naturally loose joints throughout the body.

Everyone received a single-bundle hamstring autograft reconstruction. Patients were then randomly assigned to receive that alone, or that plus a modified Lemaire LET. Because assignment was random, the two groups were comparable at the start, which is what makes this a stronger form of evidence than a study comparing one surgeon's patients to another's.

A total of 436 patients (87.9%) came in with high-grade rotatory laxity before surgery, and 215 (42.1%) had generalized ligamentous laxity. These were, by design, difficult knees.

Patients were followed for two years. The main outcome was failure, defined as either needing a revision ACL reconstruction or having symptoms of instability along with a persistently positive pivot shift.

What they found

In the group that had ACL reconstruction alone, 120 of 298 patients (40%) met the definition of clinical failure, compared with 72 of 291 (25%) in the group that also had a LET.

Actual graft ruptures followed the same pattern. There were 34 ruptures among 298 patients (11%) in the reconstruction-only group, compared with 11 among 291 (4%) in the group that received the added procedure. The authors calculated that roughly 14 patients would need a LET to prevent one graft rupture over the first two years.

The trade-off showed up early in recovery. At three months, patients who had the ACL reconstruction alone reported less pain on two different measures, and the difference in knee pain scores continued to favor that group through six months. By the later time points, that gap closed.

How to read that 40 percent

This is the number that tends to alarm people, so it is worth slowing down on.

Forty percent did not retear their ACL. The retear rate was 11 percent. The 40 percent figure includes every patient who had a positive pivot shift on exam along with symptoms, whether or not the graft was actually torn. That is a deliberately strict definition, chosen because leftover rotational looseness is the exact problem the study set out to address.

It is a fair way to measure what the operation is supposed to fix. It is not a number to carry around as your personal risk. Keep in mind too that this trial enrolled young patients selected specifically because they were high risk, so the failure rates here are meaningfully higher than what an average patient having an ACL reconstruction should expect.

So which patients need an LET?

A few practical takeaways.

This is not a procedure for every ACL. The patients in this trial were young, had loose knees or a high-grade pivot shift, and were headed back into cutting and pivoting sports. Most people having an ACL reconstruction do not fit that description, and adding the procedure to a low-risk knee adds a second incision and early soreness without a clear benefit to weigh against it.

The patients who do fit that description gain real protection. A drop from 11 percent to 4 percent in graft rupture over two years is a meaningful difference for a high school or college athlete who plans to keep playing.

Expect a little more discomfort early on. There is a separate incision on the outside of the thigh, and that area tends to be tender for the first few months. Patients in this trial reported more pain through six months, and then caught up.

Rehabilitation does not change much. The added procedure does not slow down the ACL recovery timeline in any meaningful way, and the return to sport decision is still driven by strength, movement quality, and time.

What we still do not know

Two years is a reasonable window for this question, since most graft ruptures happen in the first two years after surgery. It is not the whole story. Longer follow-up of these patients is ongoing, and the smaller groups available at later time points make firm conclusions harder to draw.

There has also been a long-standing question about whether adding a restraint to the outside of the knee could make it too tight over time, or contribute to arthritis on that side of the joint. Nothing in this trial suggested that within two years, but it remains a reasonable thing to keep watching.

Take Home Message

An ACL reconstruction restores the ligament. It does not always restore rotational control, and for a young athlete going back to a pivoting sport with a naturally loose knee, that gap is where retears live.

The STABILITY trial is the clearest evidence we have that closing that gap with a lateral extra-articular tenodesis lowers the chance of failure in exactly those patients. The cost is a small second incision and a few months of tenderness on the outside of the knee.

The right question in clinic is not whether the procedure works, because this study answers that reasonably well. It is whether your particular knee, your sport, and your goals put you in the group that stands to benefit.

A note on how I approach ACL surgery:

ACL reconstruction is a large part of my practice, and I perform it with every graft option, including bone-patellar tendon-bone, hamstring, and quadriceps tendon when it is the right fit. There is no single graft that is best for everyone, and the same is true of the lateral extra-articular tenodesis. I add one when a patient's exam, sport, and anatomy point toward a higher risk of retearing, and I leave it out when they do not. That decision gets made together, in clinic, after we have talked through your goals and I have had a chance to examine your knee and review your imaging.

About the author

Joshua R. Eskew, MD is a fellowship-trained orthopedic sports medicine surgeon at Prisma Health's Steadman Hawkins Clinic of the Carolinas in Greenville, South Carolina, and an Associate Professor at the University of South Carolina School of Medicine Greenville. He completed his sports medicine fellowship at the Hospital for Special Surgery in New York, where he served as Administrative Chief Fellow. He serves as team physician for Presbyterian College athletics and the Hub City Spartanburgers.

This post is for general education and is not medical advice. Every knee and every athlete is different, and decisions about surgery should be made with your own physician, who can examine you and review your imaging.