Does Size Matter?

Short answer… Yes! But what exactly are we talking about here? And who are you asking?

Depending on those audiences, answers may vary.  But when it comes to anterior cruciate ligament reconstruction (ACL-R) and graft types, it’s clear that size plays a role in failure rates.  ACL-R research has come a long way over the last few decades and techniques are only improving. 

Did you know that they used to cast knees after ACL reconstruction? Yes, a cast… on the knee… it’s crazy to think about in 2021.  A cast means increased muscular atrophy, more impairments in mobility, possibility of knee flexion contractures and reduced tissue extensibility.  The rehab process involved after being casted would have been a pain in the a… well knee.

The gold standard for ACL-R has traditionally been BPTB (bone patellar tendon bone) grafts because it gives a better “fixation” spot as bone heals into bone pretty well.  However, literature has reported figures as high as 30% of BPTB patients suffer from chronic anterior knee pain [1, 2]. 

So, are there any other options out there? Of course, and I feel like you already know I was going to say that. Another great option is the hamstring tendon graft which has typically been known to be stronger than the BPTB.  When it comes to which technique is used, it usually depends on a couple factors.

#1 Surgeon Preference

#2 Injury Incidence

#3 Patients History

Surgeon preference is just that, whatever the surgeon prefers.  No matter what surgery you have, there’s typically a surgical technique that your doctor may prefer, and I’m talking about any surgery.  Whether it be on the shoulder, elbow, knee, etc.  This is why docs tend to have certain protocols and post-op precautions that may differ from others.

Injury type or incidence is another.  How did the ACL rupture in the first place? Was it contact or a non-contact injury?  A non-contact injuring may suggest that the person has poor motor control and impaired movement techniques that put them at a risk for that tear.  In that case, it may be better to preserve their hamstrings because they need all the stability at the knee that they can get, and therefore BPTB graft would be a higher consideration.

If it were a contact injury where someone or something ran into them, then hamstring graft would be a good consideration because it tends to be stronger graft.  Especially for anyone who plays competitive sports and will essentially need to return to that high level of play.

Lastly, we have the patients history.  Are they high level competitive athlete who makes a living out of an elite sport? Are they a housewife who doesn’t need to be a mobile as the athlete, but needs to be able to stand and walk all day? Or are they sedentary individual who sits at a desk all day doing paperwork?  Depending on what they need to be able to get back to doing, their graft should match their activity level.

Now of course these factors may be different for other clinicians, this is all in my opinion from treating ACL-R over the last 10 years. 

If you have other factors that you would put on your list of considerations in ACL-R technique, please reach out to me and let me know.  I’m all about learning and growing and would love to see what you guys think plays a major role in treatment as well.

But getting back to my post…

A downfall with using a hamstring autograft is the success of the surgery relies on larger diameter grafts [3].  Which means that SIZE DOES MATTER!

So, ladies, when a guy asks you “does size really matter?” You can confidently say, “yes, you damn right it does,” and then go into explaining this study in SICOT-J 2021, 7, 16.

You can read the study at the link for full details about the method used and results.  The gist of the study was to investigate whether or not the 4-strand hamstring autograft diameter influences failure rates in ACL-R.

What it ultimately found was that patients with a 4-strand diameter < 8mm were 7.2 times more at risk for ACL-R failure.  There is a significant correlation between 4-strand autograft diameter size and the need for ACLR revision surgery. 

That being said, when we use autograft that means we are using our own tissue from our bodies.  No two people are built exactly the same and no two tendons are exactly the same.  Some individuals may not have thick enough tendons to get to the diameter requirements and therefore are typically needing to use more strands. 

Now, are we compromising the motor control aspect of the hamstrings at this point if needing to harvest more strands? I honestly don’t know but feel it’s good food for thought. 

Although graft diameter plays a major role in the contributing factors of ACL-R failure, we must remember that failure is multifactorial.

What I hope you get from this post is that the conversation in the ACL-R world is constant and everchanging; When it affects you, you should be a part of the conversation and decision making. 

Keep a look out for my next blog… What if… you don’t even need surgery at all? Can the ACL heal on its own?  Is there a whole new option that we should be considering more?

1. Hamner DL, Brown CH Jr, Steiner ME, Hecker AT, Hayes WC (1999) Hamstring tendon grafts for reconstruction of the anterior cruciate ligament: Biomechanical evaluation of the use of multiple strands and tensioning techniques. J Bone Joint. Surg Am 81, 549–557.
2. Hamido F, Al Harran H, Al Misfer AR, El Khadrawe T, Morsy MG, Talaat A, Elias A, Nagi A (2015) Augmented short undersized hamstring tendon graft with LARS artificial ligament versus four-strand hamstring tendon in anterior cruciate ligament reconstruction: Preliminary results. Orthop Traumatol Surg Res 101(5), 535–538.
3. Ma CB, Keifa E, Dunn W, Fu FH, Harner CD (2010) Can pre-operative measures predict quadruple hamstring graft diameter? Knee 17, 81–83.