Is there about to be a revolution in ACL surgery?

Posted on April 6, 2016

(Last Updated On: May 19, 2017)

I’m listening to some One Direction when my girlfriend comes over, “Have you seen this?” She shows me the following video:

She found this while scrolling her Facebook newsfeed. 99% of what’s found on there is more hyperbolic than Mark Zuckerberg thinking he’s connecting everybody, when really we all just want to know if our ex from five years ago made the wrong decision. Put your strap on and ingest a drug, it’s time to go balls deep…into some research. So seriously, get a cup or two of coffee to stay awake and use the strap to keep you in your chair.

DuckDuckGo (try it instead of Google) this procedure, or Martha Murray, one of the primary inventors of it, and here are some things we get:

Boston Globe No Cutting No Surgery ACL

WOW! No cutting; no surgery??? How the hell did they get in that knee in the first video we watched?

Fast Company Martha Murray

Amazing. I’m confused though because I tore my ACL; now I have a new one, and it works, so it was fixed, no? I guess fix is a matter of interpretation.

From a Youtube video:

Boston Children's Youtube revolution ACL

One of the purported benefits of this approach is it being less invasive. From an article:

ACL bio repair quote

This is an odd quote.

  1. In the Bridge Enhanced ACL Repair, we’re introducing a foreign body. The bridge or sponge.
  2. You currently don’t have to harvest a graft from a person. You don’t have to damage another part of the body. We have allografts, which are grafts taken from a donor.

How the media portrays this matters. How Boston Children’s HOSPITAL portrays it matters. How the researchers allow it to be portrayed matters. We get it. Funding is tough. “The United States doesn’t invest in itself!” or whatever complaint you want to conjure up. “Publish or perish,” even if that’s been thrown around since the ’90s. Even if funding went up through the 2000s. By like seven billion dollars.

NIH Funding with line

Green line.

But still, we get it. Garnering attention for your work can be tough. But this is the type of stuff where people go,

Rob ACL new surgery comment some blocked out

From a comment on my site.

If you’re promoting a revolution, it better at least have remnants of one.

The surgery (yes, it’s still surgery)

Let’s quickly recap what our baseline is. A reconstructive ACL surgery consists of:

  • We harvest either an allograft or autograft (from your own body) to replace the torn ACL.
    • Most of us want an autograft. Allografts tend to be subpar for a variety of reasons. Yes, even though you gain the benefit of not cutting another part of your body. To make this more obvious, the most noteworthy group tearing their ACL, NFL players, only do autografts. If allografts were better, with all those millions on the line, they’d have likely figured that out by now.
  • Next we drill holes through the tibia and femur. These holes allow us to insert our graft.
  • We screw the graft in place in those holes.
  • Wah-pah!, we’re done.

Chandler Wah Pah GIF

There appear to be two main studies which have propelled this Bio Enhanced ACL Repair into revolution territory.

Biomechanical outcomes after bioenhanced anterior cruciate ligament repair and anterior cruciate ligament reconstruction are equal in a porcine model

Use of a Bioactive Scaffold to Stimulate ACL Healing Also Minimizes Post-traumatic Osteoarthritis after Surgery

Let’s look more closely at what the Bio-enhanced ACL Repair consists of:

“Bio-enhanced ACL repair obviates the need for graft harvest and can thus be a less invasive procedure.”

To reiterate, we already have something which can do this. This is repeated in a variety of mediums, so we’ll continually refute it. Let’s get more into the procedure though. From one of the papers; bolding mine:

“For the animals randomized to the bio-enhanced ACL repair group, tunnels in the femur (4.5 mm) and tibia (2.4 mm) were created in the standard positions for ACL reconstruction, with the tibial tunnel exiting in the center of the tibial attachment and the femoral tunnel placed in the center of the femoral ACL attachment site. A drill guide and a 6-mm-offset femoral aimer were used to place 2.4-mm guidewires. The femoral guidewire was overdrilled with an EndoButton drill (4.5 mm), and an EndoButton armed with 3 No. 1 Vicryl sutures was placed through the femoral tunnel and engaged on the femoral cortex. A Kessler suture using No. 1 Vicryl was placed in the tibial stump of the ACL to repair the transected ligament. Vicryl is an absorbable suture that completely dissolves in approximately 63 days. Two of the EndoButton sutures were threaded through the collagen scaffold, passed through the tibial tunnel, and tied over a button with the knee in full extension. The scaffold was saturated in situ with 3 mL of the platelet concentrate. The remaining suture from the femoral tunnel was tied to the suture in the tibial ACL stump to reduce the ACL and secure it. The collagen-platelet composite was observed for 10 minutes to ensure that clotting occurred before the incisions were closed in layers with absorbable sutures.”

I had to re-read this a few times…we’re still drilling! In the same positions as a standard ACL reconstruction. Let’s go back to our initial video:

ACL bio enhanced repair 1 ACL bridge enhanced repair 2

Now one could either say I missed this, or one -I- could argue it wasn’t exactly made clear in the video these were drilled tunnels:

ACL bio enhanced repair 1 with tunnel outlines

And I’m not the only one who thought this:

Rob ACL new surgery comment with drilling

As of right now we are,

  1. Introducing foreign bodies with sutures and this sponge which has foreign cells on it
  2. Drilling tunnels

“An important point that steered us toward the use of skeletally immature animals is the current, particularly high need for improved ACL treatment options in pediatric patients. ACL reconstruction is still avoided in many skeletally immature patients because of fear of growth disturbances, leading to secondary cartilage and meniscus injury in these conservatively treated patients. […] The technique presented herein could be an effective option for skeletally immature patients leading to an anatomic repair without affecting the growth plate.”

This is a lot of confidence considering the drilling -again, being done in the same positions- is still going on. The drilling can be less in diameter in this new procedure compared to a reconstruction. Hey, less of your bone being power drilled is nice. Are millimeters in this instance going to matter? Who knows, but sure, it’s worth doing if available and might make a difference. Might.

Yes, we are doing things differently in how we fix the ACL. Heal the original vs replace it. But how we get there is awfully similar so far. Drill holes => Insert a material. A big difference right now being we’re inserting a foreign material vs our own tendon.

Issues with methodology (man’s best friend is not the same as man’s knee)

I’ve had the amazing benefit of personal training a veterinarian surgeon the last few years. We’ve had many discussions (I should probably be paying him some) on dog ACLs. The BioEnhanced Repair used pigs for their jumping point research papers.

Here is a dog:


Very similar leg anatomy. The big thing here is notice how the knee of these animals is, in neutral, in flexion compared to a human:

dog knee anatomy 1 with landmarks

Where a human leg, in neutral, goes straight down:

dog knee anatomy 1 relative to human

Because a dog’s knee is placed in a position of flexion, it relies on an ACL more than a human. As we flex our knee, the stress on the ACL goes up dramatically. It gets harder and harder to prevent anterior tibial translation relative to the femur. (This is the ACL’s job.) The shin becomes more and more likely to move forward.

ACL Lachman with drawing and anterior translation

Tibial thrust canine ACL

The tibia is thrusted forward of the femur, so the ACL, which lies between the femur and tibia, has to pull the tibia back.

Animations made from this video:

Femur on top; tibia on bottom; ACL in between. (Animation made from this video:

This why in dogs ACL reconstructions are not done. Between the lack of ability to control the animal in the post-op phase and the extra stress on the reconstruction, the failure rate is too high. The dog either rips the graft hardware apart or the graft stretches out so much making it worthless. This is crucial. Reconstructions are not done in dogs. They used to be, but the failure rate was so high veterinarian surgeons stopped performing the procedure. Instead the anatomy of the tibia is reoriented to make the leg not as reliant on the ACL. Here is a fantastic video if you want to watch. It’s a good way to learn more about how an anterior cruciate ligament works:

The pigs used in both of our jumping point studies had ACL reconstructions.

Yet none of the above is mentioned as a caveat in the studies.

Even worse, the pigs had this reconstruction inserted with the knee in full extension. This would be analogous to placing the graft in a human with the knee in a position like this:

knee hyperextensionFull extension to a quadruped is hyperextension to a human. (It’s out of neutral.) When the knee is hyperextended the ACL is stretched. You don’t want to place a new ACL in a stretched position. You want to place it in a shortened position. You know the graft is likely going to stretch some, so you start with it in an excessively shortened position so when it does stretch, hopefully it only stretches to what would be neutral for a regular ACL. Place it in neutral, or in a stretched position, and it will stretch to where it’s excessively lax. (How surgeons do this with humans.)

We’re comparing the Bridge Enhanced Repair to a crappy treatment. In the least, you can say,

  • ACL reconstructions fail in quadrupeds
  • If the bridge enhanced repair gets similar numbers to the quadruped reconstruction, then it is worthless in quadrupeds, but may be similar to a reconstruction in a person, which tends to work decently well.

In other words, the Bio Enhanced Repair better be as good or better than this reconstruction for it at all to be considered noteworthy. Because a quadruped reconstruction is already inadequate to such a degree it is not even done! We’ve immediately biased these studies away from the reconstruction group. “Let’s see if this procedure is as good as a treatment which doesn’t even work.” Again, there could be application to humans from that, but that’s a big gap to bridge. Just because two things fail equally in one animal does not mean they’ll succeed equally in another animal.

So, was it as good or better?



Range of motion and muscle size

Range of motion is crucial after ACL surgery. As is not losing muscle bulk. Comparing:

ACL repair vs reconstruction circumference and range of motion

To get oriented, ACL transection means they cut it and left it that way. Next, you may be wondering why circumference increased. We don’t usually get more muscular after surgery! That’s because this was done in adolescent pigs. They grew bigger as they grew older.

The enhanced ACL repair group had a statistically significant increase in thigh circumference compared to the ACL reconstruction group, but not compared to the lacking ACL group, which is quite strange. (To be clear, having no ACL was as good as the bio repair.) The authors mention the reconstruction group could have been lacking due to the larger tunnels required, causing something like an increased inflammatory response => more pain => use the thigh less. Or

“the persistence of a subclinical effusion in reaction to the allograft material, which could potentially limit leg usage in the postoperative period.”

The gold standard of ACL tear treatment (in humans) is ACL reconstruction with an autograft. Why are we using allografts??? The authors say because using a bone patellar bone graft in a pig would mess up the knee extensor mechanism. So why not use a hamstring graft then? The authors say autografts are not regularly available. I asked my veterinarian surgeon client about this. “You can get a tendon from anywhere.” The authors say the allograft reconstructions were similar to autograft ones in other studies (somehow harvesting a graft wasn’t a problem for them). Then why mention a potentially increased inflammatory response from an allograft? Because they aren’t similar!

-> Bringing up another point. Who performed these surgeries? It looks like orthopedic surgeons. Human ones. I can’t find anything but MDs on the paper. No DVMs or VMD (vets) are even cited. I’ve been in a human operating room and a veterinarian operating room. The veterinarian surgeon purposely waited until he had a large dog I could watch. Small dogs you can’t see anything as an outsider. Even a large dog though and it’s a lot smaller in there than a person.

A juvenile pig? That’s a very small knee compared to a person. By these authors own definition, ACL reconstruction is a more involved procedure. If a human doctor, one has to wonder how good of a job these surgeons were able to do with pig knees, when they aren’t used to dealing with anything that small. This may have immediately biased the study. (As well as how delicate were these surgeons with an animal compared to a human? Did they give the same level of care?)

And maybe this is why they used allografts. A human doctor isn’t familiar with harvesting a graft from a pig.

And does a pig require normal ACL tunnels drilled? Maybe the reconstruction tunnels were unnecessarily large?

But back to this:

ACL repair vs reconstruction circumference and range of motion

The thigh circumference is something to be mindful of. Now, while not statistically significant, those who deal with ACL patients may not agree the range of motion numbers aren’t clinically relevant. While the reconstruction group lost not even a degree of range of motion, the ACL repair group lost four degrees of flexion and three degrees of extension. If that happens to someone, you worry about it. Especially the extension. Granted, in a human, you could likely rehab your way to normal numbers.

You could likely do the same with thigh circumference!


This is Big Papa. We can usually rehab our way out of range of motion or muscle bulk issues. We largely can’t rehab our way out of how strong the new ACL is. That’s primarily dictated by the procedure. (We can eff it up in rehab i.e. we can make it weaker / stretch it out; we just can’t make it stronger.)

In one study, after 15 weeks things were quite similar in the pigs. (They showed a reconstruction -a crappy treatment- is similar to their treatment.) In their follow up study they looked at things at six months and one year. That’s more relevant.

The numbers are in relation to the non-operated leg. Zero would be no difference. We want to be at or close to zero.

Stiffness comparison ACL repair and reconstruction

Yield load comparison ACL repair and reconstruction Max load comparison ACL repair and reconstruction

The way the authors did this was for each time point, 6 and 12 months, bars which have the same letter “did not differ after Holm adjustment.” Somehow this came out to where:

Stiffness comparison ACL repair and reconstruction with lines

For stiffness, the ACL reconstruction group, which at six months has no difference compared to the good leg, is not different than the Bridge Enhanced ACL Repair. Regardless of what statistics says, part of you has to go, “Ok, one group had no difference, and another group had a noticeable difference. That has to matter.”

-> Can’t recommend this paper enough:

Toward Evidence Based Medical Statistics: The P-Value Fallacy


Max load comparison ACL repair and reconstruction lines 2

At 12 months, the ACLR group is at ~600 newtons. The BE repair group is at ~11o0 newtons. That’s nearly doubly worse. This somehow statistically came out as “no difference.” The people doing this research seem very nice from seeing interviews with them. But the cynic in me is remembering chapters from the book “How to Lie with Statistics.”

In a talk on this paper, the following two slides were presented:

Murray talk one year comparison ACL Murray talk 15 week comparison

Let’s play that game- can you find what’s different between the photos? Why did max load mysteriously disappear in the second slide above with the longer follow up?

Max load comparison ACL repair and reconstruction lines 2

Empathetically we might say “They forgot it.” Cynically we might say “Because that had a big difference, where the other two measures weren’t as different. So they only showed the ones which were in their favor. Showing those other bars wouldn’t look too good.”

Even ignoring this, we’re still talking pretty big differences here, albeit not statistically significant. The yield load difference looks to be about 17% here. ~.6 compared to ~.43. (In these slides, you want to be close to 1; not zero.)

Murray talk 15 week comparison

All statistical significance means is some level of confidence to say the results weren’t due to chance or something like sampling error, or they match up well with some model we already have. It doesn’t mean the results don’t matter or are insignificant. We’ll come back to this.

-> This is when you tighten your strap and start drinking the second cup of coffee:

A p-value of .05 or less usually means you reject the hypothesis. In this case we’d reject the hypothesis of there being no difference between the ACLR and BE-repair, aka there is a difference. For strength, they got a p-value of .57, which is greater than .05, meaning we can’t reject the hypothesis of there being no difference between the two. That does not mean the hypothesis is true! It means we can’t reject it. It could be true; it could not be. And that doesn’t mean there wasn’t actually a difference. A potentially clinically relevant one. Statistical significance is not synonymous with clinical significance. We just didn’t hit the threshold where we could say “It’s unlikely enough the difference wasn’t due to something aberrational.” It means given the hypothesis is true, there is a 57% chance we get the results we got. Meaning there would be a 57% chance the ACL reconstruction would be better! Again, we’ll come back to this.

–> Also worth reading:

Misunderstandings of p values

American Statistician Association statement on p-values

Richard Thisted- What is a p value?

In that same talk, a recent patient of the bio-enhanced ACL repair came on to speak. He presented this slide, and discussed hamstring strength:

Hamstring strength post acl

I’d bet my car that ACL reconstruction consisted of a hamstring autograft. If we want to make a fair comparison, why aren’t we comparing allografts? That’s what we did with the pigs. We picked a procedure in pigs which we know is not as good, but then in humans we picked a different procedure, which we know is going to not give great strength results at six months- the hamstrings need some time to come back, and it’s true 100% likely won’t happen. The numbers are conveniently fitting a narrative.

Furthermore, if we’re going to put the hamstrings on blast at six months, why aren’t we putting this on blast?

Stiffness comparison ACL repair and reconstruction six months Yield load comparison ACL repair and reconstruction six months

Max load comparison ACL repair and reconstruction six months

In every case the BE-repair is doing worse than the (crappy) ACLR at six months. (In every case it does worse at 12 months too.) Even with the statistical method they used, the method says max load is worse at six months. In other words, if the BE-repair group were better than the ACLR group, no matter how small, would that have made its way on a powerpoint slide?

“The linear stiffness and yield load values for all three surgically treated groups were similar at both 6 and 12 months. Although there was no difference between the untreated ACL transected ligaments and the bio-enhanced ACL repaired ligaments at 6 months, the yield load of the bio-enhanced repair procedure continued to improve and became significantly different from the transection control at 12 months.”

These statements are opposition to one another. Let’s break it down. Below is linear stiffness and yield load at 6 and 12 months. Looking at six months, based on the lettering, the surgical groups are all “similar.” They all share the letter b.

Stiffness comparison ACL repair and reconstruction shared letter b Yield load comparison ACL repair and reconstruction shared letter b

However, what’s critical to note here is the group which had no ACL was not different than the group who had a bridge enhanced repair. At six months, the ACLT and BE-repair also share letters (a).

Stiffness comparison ACL repair and reconstruction shared letter A Yield load comparison ACL repair and reconstruction shared a

But, the ACLR does not share those letters. The ACLR and BE-repair are different. Just not in the way the authors want to phrase it. Plus, in yield load, at 6 months the ACLT is at what, 850 N, while the BE-repair is at, what, 800? But the repair is “similar” to the ACLR (~250 N) while the ACLT is not? Some common sense needs to take over here.

Furthermore, the BE-repair group doesn’t exactly improve. It essentially stays the same or gets worse. It’s just the (crappy surgery we expect to get so much worse vet surgeons don’t even perform it) ACLR group gets even more worse from 6 months to 12 months, making them more similar. But, the ACLR group is still better.

Yellow lines are steeper than purple lines, yet still below:

Stiffness comparison ACL repair and reconstruction comparitive lines Yield load comparison ACL repair and reconstruction comparitive lines Max load comparison ACL repair and reconstruction comparitive lines

Beyond the strength implications, another reason we need to harp on all this is a purported benefit of this study is quicker recovery. Yet, at 6 months, this procedure, from the ACL point of view, is worse than a normal reconstruction. And that’s with a subpar allograft.

We can even see in this document it stated the repair is “about as strong.”

Bridge acl repair about as strong

Sure, it was also “about as weak as having no ACL at 6 months and 12 months.”

In this FDA proposal-

Bridge-enhanced ACL repair: A review of the science and the pathway through FDA investigational device approval

they say “This technique has shown promise in preclinical models – with ACL repair strengths similar to that of ACL reconstruction at 3, 6 and 12 months after surgery.” Again, not true, regardless of how you want to look at it:

Max load comparison ACL repair and reconstruction


“The bio-enhanced ACL repair technique resulted in protection of the articular cartilage in the porcine model. The mechanism behind this is unknown and the focus of ongoing research. Following ACL injury it is well known that joint kinematics, and hence cartilage loading, are altered, which in turn could negatively affect cartilage metabolism. Although ACL reconstruction and repair procedures attempt to restore joint kinematics, evidence suggests that this attempt is not completely successful. Examination of the AP laxity values from the four experimental groups demonstrates that normal kinematics were not restored in the present study. Other factors besides joint kinematics must therefore play a role in chondroprotection following bio-enhanced ACL repair.”

So the bridge repair group had better results for lessening arthritis post-op, but not because of joint kinematics. While we won’t see this in the headlines, it is crucial to note this procedure is not in any way better when it comes to restoring joint kinematics. The knee is just as lax after this surgery as it is after a (allograft) reconstruction.

-> In fact, the reconstruction held tighter at 30 and 60 degrees of knee flexion, while the repair did a little better at 90 degrees. 30 and 60 degrees of knee flexion is more relevant. Most of us aren’t testing the laxity of our knees at 90 degrees of knee flexion. (e.g. We don’t bend our legs that much when we play soccer.) But we again run into some statistical significance issues. Hopefully we see the theme here though as I’m sure people have had enough bar graphs for one post.

So the authors go into all sorts of explanations for why arthritis was less. They want to try and explain these pictures:

Arthritis after different ACL surgeries 1

Why is C so much cleaner looking? Even if that arrow seems to be ignoring this:

Arthritis after different ACL surgeries 2

Which suddenly doesn’t look too dissimilar from B’s arrow.

But anyways, they looked at both condyles, so it’s a fair question. Why might a repair have lesser arthritis rates? We have our smaller drilling hypothesis, lesser inflammation from not using an allograft, maybe the extra blood on the sponge does something. An interesting possible explanation was the authors stating that in an ACL repair perhaps more of the proprioception within the ligament is preserved (I’ll try to explore this in another post), which can apparently talk to the hamstrings, helping to provide dynamic stabilization. (The hamstrings perform a similar job as the ACL, in terms of preventing anterior translation of the tibia.)

One explanation they didn’t examine is the pigs with the allograft had smaller thigh musculature than the enhanced repair group. Again, why, who knows. But smaller muscles are weaker muscles. A weaker thigh can be more likely to get arthritis.

Another thing the authors don’t mention- we have a gargantuan sample size of 32. 8 for each group. After 12 months, there were only 7 in the bio-enhanced repair group. Our main comparison is the reconstruction group of 8 vs the repair group of 7. Not tough to imagine some weird things happening when your sample size is that small! In a study size of one! And perhaps now we know why we consistently see the reconstruction group do better in multiple measures of strength and laxity, over multiple periods of time, but we don’t hit statistical significance. A bigger sample size might be the answer.


Normal ACL:

Intact ACL

The reconstruction group after six months:

Reconstruction 6 months histology

Bridge / bio enhanced repair six months:

BE repair 6 months histology

And after a year:

reconstruction 12 months histology BE repair 12 months histology

You can see things look similar, as the authors say. Histologically, doesn’t look like anything is healing faster in the repair group.


From the FDA proposal:

“For scaffolds incorporating biologic elements, additional concerns must be addressed, including methods for minimizing potential contamination during manufacturing (particularly for products that cannot be terminally sterilized), proof that implanted cells will remain in place, and reasonable data to support the assurance that growth factors will be delivered in such a way as to only affect the target cells.”

“Under aseptic processing conditions without terminal sterilization, the scaffolds produced in our laboratory were implanted in over 500 animal knees, with only one infection seen after surgery. This suggests that aseptic processing was reasonably effective in minimizing contamination of the scaffold. However, when the stricter sterility testing required for clinical devices was performed (Microtest), five out of five scaffolds failed the testing, suggesting there remained small numbers of bacteria contaminating the scaffolds.”

It is extraordinary what goes into sterilization. The authors admit how costly it can be. And as we can see, we are adding something we need to be extremely diligent about, which has a risk of infection.

The tradeoff here is we are putting the foreign body, as well as cells (for the scaffolding), directly into the joint and leaving them there. With an autograft ACL reconstruction, the foreign bodies are placed outside the joint, above and below the knee. The joint is less at risk. It may be a very small risk we’re adding here, but infection rates tend to be small, yet common enough a great deal of us know someone it’s happened to.

Closing up

I liken this to The Big Short. Michael Lewis, the author, as well as his subjects -those who saw the crash coming- still aren’t really sure the mindset behind it all. Was it idiocy, ignorance, delusion, corruption? A combination? Did Wall Street purposely convolute things so much so they could sell it as they only know what’s going on? Making us feel like we need them (corruption)? Or did they convolute it so much to help them rationalize (delusion)?

The people working on this new ACL procedure are unlikely corrupt. (Whereas some people working on shockwave therapy probably are.) Certainly not idiotic! But a big problem with science right now, and reporting on science, is making a bigger deal out of results than they really are. Causing reactions like this:

Rob ACL new surgery comment with drilling

The hyperbole of everyday studies is through the roof.  Part of this is surely wanting to make a positive impact on the world. Part of it is unconscious and innocent. But part of it is mere click bait. Trying to grab as many likes with a science headline as one about Harry and Swifty, which will never happen.

To be fair, in this video Martha Murray states the procedure as being “a little less invasive.” But we shouldn’t have to go 20 minutes deep into an obscure lecture to find one sentence calming down article after article of rhetoric. (Again, not only putting this on the researchers. The media isn’t doing its part either.) Me, some schmuck with a website, shouldn’t have to go nearly six thousand words deep to weed this all out.

To also be fair, it’s not unreasonable to see Martha Murray herself has received $8.8 million in funding just from 1999 to 2012 for this new ACL procedure, and no matter how good of people those working on this are, there could be some unintentional bias going on when you have that much riding on this.

Nor should we have to go “Hmm” when we go into Martha Murray’s CV and find she was a “Scientific Founder” and on the board of a company called Connective Orthopaedics, a company (who was?) working on ACL repair technology. 

Murray connective orthopedics

That she was working for this company while conducting the two research studies we’ve been discussing-

Her declarations of funding.

Her declarations of funding.

And has a few patents for all this stuff:

Martha Murray ACL patents Martha Murray patents ACL 2 Martha Murray patents ACL 3

Yet none of this is declared as a conflict of interest in the studies?

No conflict of interest statement bio enhanced ACL repair

When it looks like she was one of the surgeons performing the reconstructions on the pigs? Might she have an interest in how those reconstructions come out?

She did declare having a patent as a conflict of interest in one of her talks


At the end of the day,

  • The ongoing human trial is based on a procedure which largely did not do as well as a treatment which fails in quadrupeds
  • We still haven’t compared the gold standard of treatment (autografts) to the new procedure. Looks like this is just getting going in the human trials.
  • We’ve only been privy to one human subject who has received the procedure
  • We’re still drilling holes
  • We’re still introducing foreign bodies, except now it’s into the joint, as well as adding foreign cells
  • The strength of the ACL is so far, if anything, less than current treatment
  • If there is any difference in joint kinematics worth noting, it’s that the repair is overall more lax than an animal reconstruction
  • Nothing to suggest recovery will be quicker
    • Healing the harvested graft is not the bottleneck with ACL recovery. Healing the new ACL is.
  • Potential for less arthritis, but with no explanation for why that is, leaving a clear door open for randomness or bias

How’s that one human subject we know about doing? Cory Peak is the flagship patient for this procedure right now, as he was the first to have it, and is doing quite well. He wrote about his experience here. I don’t feel bad picking on him because he’s a doctor of public health at Hahvahd. Bolding mine:

“It’s been more than a year since I tore my ACL. I am far along on the road to recovery; I’m especially appreciative of refreshed feelings of optimism and freedom and enjoying my return to a mobile, active lifestyle.

I’m optimistic that I will make a full recovery on a similar schedule while recovering from ACL reconstruction.”

This article was published 13 months after his surgery. More than a year out and he’s still recovering. Doesn’t sound like he’s recovering any quicker, does it?

“The first two weeks after surgery were the hardest. All ACL patients have to wear a restrictive hip-to-ankle, post-operative brace for about six weeks. On the positive side, I was encouraged to see progress every day. I celebrated small victories, like bending my knee enough to sit on a chair and walking without crutches along the Charles River.”

Sounds like what any ACL patient will tell you.

Some of the articles, as well as him, have referenced how he’s biking, running, and hiking again, with no problems. You can see a picture of him hiking in one of the slides from earlier:

Hamstring strength post acl

You don’t need an ACL to do those things! We have literally zero research on whether this procedure will give similar functional results on the most demanding ACL activities. We have research on indicators (and they’re not very good), that is all. Sure, you start somewhere. But you don’t extend Sam Adams shooting the shit while drunk saying “Let’s piss on the queen” to “There’s a revolution going on.” A lot of other things had to happen.

However, there is no doubt if we can get the same results without harvesting a graft, that’s great! And some things are looking promising, like the potential to preserve proprioception within the ACL, but currently results show a graft which is not as strong and more lax. If we’re talking getting back to a high level of physical activity, every iota counts with ACL stuff. Personally, if this procedure were available to me when I tore my ACL, I wouldn’t have opted for it. And wouldn’t even think to opt for it without a minimum of a five year follow up on a large sample (>100) being done. That should be accomplished in oh, 15 or more years from now.

-> Not to mention I wouldn’t have qualified for it. Currently you need to have a particular type of tear e.g. have enough of the old ACL left over and have the surgery within 30 days of tearing the ACL. Many don’t know they tore their ACL for monthS. Good luck getting an appointment with your primary care doctor, getting an appointment with an orthopedist, then a date for surgery, all within a month of tearing your knee up.

Beyond being a guinea pig -which I realize medicine has to practice and experiment like anybody else, just practice on someone else, not me- the lesser strength would highly concern me.

There are mainly two types of people who should get ACL reconstructions:

  1. Those worried about intense physical activity, requiring a good deal of cutting. Soccer, football, and the like.
  2. Those who have effortfully tried physical therapy, modified their activity to a point they’re ok with, and yet are still having significant issues with knee stability during every day life e.g. their knee gives out randomly, regularly, like when stepping off a curb.

In the first group, the lesser strength of this new procedure has to be a concern. If we’re talking professional athletes, extremely small percentages matter. You want that new ACL to be as strong as the original as possible. You will take a likely slightly less strong thigh (having to harvest a graft) in favor of a stronger ACL. (Though the potential proprioception differences can be big here.)

For the second group, first, I’m of the belief -as are others- very, very few people fit into this category. Where good exercise therapy can stabilize the knee to a point most will be ok through daily life with. Secondly for this group, we’re talking the current treatment likely being an allograft. Those who just want some knee stability to be able to go through their daily life without their knee giving out. Because they aren’t concerned with intense sports, we don’t bother with the more invasive, yet better, procedure of getting an autograft.

Which means this new procedure could be fitting for the second group. Perhaps giving them a lesser risk of arthritis. Though a very small sample of people, hey, that’d be awesome.

Finally, we can look to other things, like achilles tendon tears, or the MCL, which is the ligament this procedure was based off of (MCL tears heal without surgery), and see what the healing rate is for those: Still around a year. (Biomechanics of knee ligaments: injury, healing, and repair.) We’re trying to force the body to heal something -a ligament or tendon- faster than it can. Stitching a torn ACL back together still requires biology to take place. Ask Cory.

For a step by step guide to recovering from ACL surgery, check out The most important phase of ACL rehab

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