An ACL injury affects you mentally as much as it does physically. Many ACLers feel like they’ve suddenly had a weight dropped on them as they try to navigate the thousands of decisions required to make a successful recovery. In starting to research their recovery, they often discover some of the scary statistics around secondary injuries & failure to return to sport. They may also find information on the importance of prehab as well as the underutilized non-operative option. For those who choose to have surgery,y one of their biggest decisions is choosing the type of graft they will get. This article will make navigating this decision much easier by providing an overview of the pros & cons of each of these grafts as well as how they can affect your recovery & outcome.

 

Different Types of ACL Grafts:

The most common options are those provided via a cadaver AKA an allograft, or those provided from your own body AKA an autograft. When it comes to autografts, there are 3 primary options: the Hamstring Graft (HS), the Bone-Patellar Tendon-Bone (BTB), and the Quadriceps Tendon Graft (QT). Let’s discuss allografts first.

 

 

The Allograft:

The allograft is an attractive option for many ACLers as it can be taken from the soft tissue of a cadaver and does not require any removal of soft tissue from the ACLers own body. The main benefit of the allograft is that you avoid what is called “donor site morbidity,” meaning that while you will have to rehab & recover from the ACL reconstruction, you won’t have the additional layer of recovering from the graft that has been taken from your body. This is no small benefit as taking a piece of your quad, hamstring or patella tendon absolutely adds an additional layer to your rehab and recovery.

In a sense, the allograft presents the only option during which you aren’t rehabbing from 2 injuries as during your recovery from each of the autografts you must overcome both the trauma of the ACL injury & surgical reconstruction as well as the trauma & loss of tissue resulting from the removal of part of your hamstring, quad, or patella tendon.

At this point you may be asking “Why doesn’t everyone get the allograft?”

The answer is that there is a good deal of high-quality evidence telling us that allografts have a higher rate of re-tearing than autografts, particularly in younger & higher activity populations (1).

In addition to this, we have mechanistic studies showing that there is a delayed revascularization and recellularization of the allograft tissue compared to autografts. This means that the allograft will take longer both to have the same amount of blood supply as well as to reach the same levels of thickness & tensile strength if it ever does (2).

 

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For these reasons, the allograft is now seen as a less favorable option. This is particularly true when it comes to younger people who want to return to a high level of physical activity. Often, the argument is made that an allograft is a better choice for an older and less physically active patient. However, there is substantial evidence that this type of person can avoid surgery altogether with proper non-operative rehab, and this should be the first treatment option in this population.

 

READ: RETURN TO SPORT TESTING AFTER ACL RECONSTRUCTION

 

The Bone-Patellar Tendon-Bone (BTB) Autograft:

The Bone-Patellar Tendon-Bone (BTB) Autograft has historically been considered the gold standard for ACL Reconstruction. Primarily, this is because it is the only option that provides bone-to-bone fixation (4).

 

In layman’s terms:

Your native ACL is a ligament that is fixed on each end to the bones of your knee. The process of an ACL reconstruction means taking a tendon from another part of your body and fixing it to those same bones in your knee, and relying on that tendon to integrate with the bone to create a new ACL. In the case of a BTB, the patella tendon is taken along with bone plugs on each end of the tendon. Thus, when it is placed in position as an ACL graft it has the advantage of relying on those bone plugs to integrate with the bones of your knee to create a new ACL.

 

Theoretically, in animal studies, this should allow a faster incorporation of the graft compared to soft tissue grafts (5). However, a variety of other factors affect this graft healing/integration, and a more recent study in humans showed no difference between HS & BTB grafts at 6 & 12 months post-op (6).

Some studies have also shown BTB to have a lower rate of graft failure than HS grafts.  One meta-analysis in particular, which included 47,613 patients with a minimum follow-up of 2 years found that HS autografts, failed at a higher rate than BTB autografts (7). However, even this paper noted that “failure rates were very low in each group, the difference observed was small and there was little difference in terms of laxity” (i.e. how loose the graft was). This group also noted that a majority of the patients in their paper came from a Scandinavian registry study which is not as rigorous as a randomized controlled trial and may not be generalizable to ACLers elsewhere. The difference between the 2 grafts is summed up by their “number needed to treat analysis” which found that 235 patients would need to be treated with BTB over HS to prevent one graft rupture, which is a relatively small difference.

 

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A much larger number of studies have found no significant differences in graft failure rates between HS & BTB grafts as well as QT grafts. The largest systematic review conducted to date, which included more than 150,000 patients, found no significant differences in the rate of graft failure for HS autografts, BTB autografts, QT autografts and even allografts (8). This result is better supported by other meta-analyses, including one performed in 2022 and 2019.

Thus, given the preponderance of evidence, we can conclude that while there may be some evidence to support BTB having a lower failure rate, there is more evidence to show that this difference, if it exists, is negligible.

 

The Hamstring AutoGraft (HS)

You may be ready to stop reading now. Understandably, you may feel like even if there is a 1 in 235 chance that getting a BTB is going to reduce my risk of re-tear, I am all for it. Why would you ever consider a hamstring graft?

The hamstring graft does in fact present some pretty substantial advantages over the BTB graft, particularly when it comes to the rehab portion of this recovery.

The disruption of the extensor mechanism of the knee (by taking pieces of the bone from the patella, tibial tuberosity & portion of the patella tendon) has a profound effect on quadriceps strength and recovery. Quadriceps strength is one of the biggest predictors of functional outcomes as well as success with return to sport and decreased risk of re-tear after ACL surgery.

 

READ: HAMSTRING TO QUADRICEP STRENGTH RATIO

 

In fact, one study found that those who received a BPTB took up to 1.5 months longer to meet return to run criteria and up to 4 months longer to meet return to sport criteria (10). While this is significant, this study also found no significant differences in either return to sport testing or clinical outcomes at 1 year post-op. Essentially, those with a BTB had a longer, potentially more difficult rehab but they caught up to those with a HS graft 1 year.

A similar study found that those with BTB grafts had lower quad strength and poorer single leg than those with HS grafts at 4,6,8 and 12 months post-op. In this study those with BTB did not catch up to their HS graft counterparts until 2 years post-op (11).

 

READ: THE IMPORTANCE OF KNEE EXTENSION FOR QUAD STRENGTH

 

It is worth noting that this same study found that when it comes to hamstring strength, those with a HS graft has significantly less HS strength than those with BTB grafts through to 2 years post-op (11). Essentially, those with HS grafts never regained hamstring strength comparable to those with BTB grafts.

While this persistent deficit in hamstring strength is noteworthy, it should be pointed out that quadriceps strength has a much higher correlation with successful return to sport, decreased risk of re-tear, and improved functional outcomes.

The primary advantage of an HS graft over a BTB graft is the decreased effect on the patellofemoral area. Whereas the BTB has been linked to anterior knee pain and patellar tendinopathy and is known to be problematic for patients who kneel a lot, the hamstring graft is much less likely to create these side effects (12). However, the hamstrings are important when it comes to both sport performance and functional outcomes as well as risk of re-injury, and those who have a history of hamstring strains in particular should be wary of them.

The lack of difference in functional outcomes between these 2 grafts as noted above is one reason that they are often referred to as a “double gold standard,” with each graft having its respective pros & cons.

More recently, the QT graft has emerged in popularity with the hopes that it could provide an even better option than either of the above.

 

The Quad tendon Autograft (QT)

The growth in popularity of QT autografts is simple. Surgeons hoped to combine the pros of both the BTB and HS autografts and find a graft that would create less anterior knee pain, not have such a profound impact on hamstring strength, reliably provide great cross-sectional area than the hamstring graft, and not impact quadriceps strength as much.

While the quad tendon graft is still a disruption to the extensor mechanism of the knee, it often does not include the bony element and is taken from a larger tendon, which does not receive as much pressure when kneeling. Thus, the hope is that it would create less anterior knee pain and tendinopathy than the BTB graft.

Early studies have shown this to be the case with a 2019 meta-analysis finding QT grafts had comparable clinical and functional outcomes as well as less harvest site pain than BTB grafts and better functional outcome scores than HS grafts. Similar results were found in a 2015 systematic review (13).

 

So is the QT graft the holy grail? Not so fast.

 

While much of this research is promising, given that it has been popularized more recently, there is a lack of clear long-term data (> 10 years) investigating the results of the QT graft. In studies done with 2 and 5 year follow-up, they found higher rates of graft failure in QT grafts than HS or BTB grafts (13). Furthermore, there was an increase in failure rate from 2 to 5 years which suggests this may increase disproportionately over time in QT grafts compared to either HS or BTB.

Thus, while the QT graft may one day be the gold standard due to the stability it provides without the donor site morbidity, more long-term research is needed to determine this.

 

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Closing Thoughts

When it comes to choosing a graft type there is no clear-cut winner. There are many factors to consider, both when it comes to the abundance of research in this area as well as in your particular situation. One key factor to consider is surgical skill and comfort with a technique. You should always make sure that your surgeon is comfortable using the graft of your choice and that he has a lot of experience doing so. This is a particular consideration for something like a quad tendon graft which is a newer technique that a surgeon may not be as familiar or comfortable with. In weighing the pros and cons of each graft some things to consider are that the BTB graft may have the lowest rate of graft failure, may have the earliest integration and healing, and will likely provide no difference in functional performance at 1 year post-op.

However, it may also create a slower and more difficult rehab and present the opportunity for increased anterior knee pain and likely should be avoided if you spend a lot of time kneeling. An HS graft will likely be an easier rehab with less anterior knee pain, easier ability to regain quad strength and early achievement of functional and strength milestones. However, there is some evidence that it may have a higher rate of failure and that you may not be able to regain your hamstring strength as easily even at 2 years post-op. A quad tendon graft presents a newer option that is very promising in terms of functional outcomes and in avoiding anterior knee pain or long-term hamstring weakness. However, there is a lack of longer-term studies, and there may be some evidence indicating that its failure rate may increase more over time in comparison to the other two. Also, given that it is a newer procedure, you may want to make sure it is something that your surgeon is both comfortable and experienced in doing.

In all of these cases, having the right pre-operative and post-operative rehab plan will have the highest impact on reducing your risk of reinjury, increasing your confidence and ability to return to your sport and activities, and should be given just as much if not more weight when creating your plan of attack for this recovery.

 

References:

1. Wasserstein D, Sheth U, Cabrera A, Spindler KP. A Systematic Review of Failed Anterior Cruciate Ligament Reconstruction With Autograft Compared With Allograft in Young Patients. Sports Health. 2015;7(3):207-216. doi:10.1177/1941738115579030
2. Scheffler SU, Schmidt T, Gangéy I, Dustmann M, Unterhauser F, Weiler A. Fresh-frozen free-tendon allografts versus autografts in anterior cruciate ligament reconstruction: delayed remodeling and inferior mechanical function during long-term healing in she
3. Muramatsu K, Hachiya Y, Izawa H. Serial evaluation of human anterior cruciate ligament grafts by contrast-enhanced magnetic resonance imaging: comparison of allografts and autografts. Arthroscopy. 2008;24(9):1038-1044. doi:10.1016/j.arthro.2008.05.014
4. Kartus J, Movin T, Karlsson J. Donor-site morbidity and anterior knee problems after anterior cruciate ligament reconstruction using autografts. Arthroscopy. 2001;17(9):971-980. doi:10.1053/jars.2001.28979
5. Rodeo SA, Arnoczky SP, Torzilli PA, Hidaka C, Warren RF. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am. 1993;75(12):1795-1803. doi:10.2106/00004623-199312000-00009
6. Irvine JN, Arner JW, Thorhauer E, et al. Is There a Difference in Graft Motion for Bone-Tendon-Bone and Hamstring Autograft ACL Reconstruction at 6 Weeks and 1 Year?. Am J Sports Med. 2016;44(10):2599-2607. doi:10.1177/0363546516651436
7. Samuelsen BT, Webster KE, Johnson NR, Hewett TE, Krych AJ. Hamstring Autograft versus Patellar Tendon Autograft for ACL Reconstruction: Is There a Difference in Graft Failure Rate? A Meta-analysis of 47,613 Patients. Clin Orthop Relat Res. 2017;475(10):24
8. Haybäck G, Raas C, Rosenberger R. Failure rates of common grafts used in ACL reconstructions: a systematic review of studies published in the last decade. Arch Orthop Trauma Surg. 2022;142(11):3293-3299. doi:10.1007/s00402-021-04147-w
9. Mouarbes D, Menetrey J, Marot V, Courtot L, Berard E, Cavaignac E. Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis of Outcomes for Quadriceps Tendon Autograft Versus Bone-Patellar Tendon-Bone and Hamstring-Tendon Autograft
10. Smith AH, Capin JJ, Zarzycki R, Snyder-Mackler L. Athletes With Bone-Patellar Tendon-Bone Autograft for Anterior Cruciate Ligament Reconstruction Were Slower to Meet Rehabilitation Milestones and Return-to-Sport Criteria Than Athletes With Hamstring Tendo
11. Cristiani R, Mikkelsen C, Wange P, Olsson D, Stålman A, Engström B. Autograft type affects muscle strength and hop performance after ACL reconstruction. A randomised controlled trial comparing patellar tendon and hamstring tendon autografts with standard
12. Hardy A, Casabianca L, Andrieu K, Baverel L, Noailles T; Junior French Arthroscopy Society. Complications following harvesting of patellar tendon or hamstring tendon grafts for anterior cruciate ligament reconstruction: Systematic review of literature. Or
13. Slone HS, Romine SE, Premkumar A, Xerogeanes JW. Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results. Arthroscopy. 2015;31(3):541-554. doi:10.101
14. Galan H, Escalante M, Della Vedova F, Slullitel D. All inside full thickness quadriceps tendon ACL reconstruction: Long term follow up results. J Exp Orthop. 2020;7(1):13. Published 2020 Mar 14. doi:10.1186/s40634-020-00226-w

About the Author

Tommy Mandala

[P]rehab Writer & Content Creator

Tommy Mandala is a Doctor of Physical Therapy, Board Certified Clinical Specialist in Sports & Orthopedics, and Certified Strength and Conditioning Specialist in New York City. He is the founder of ALL IN ACL, a digital coaching platform dedicated exclusively to helping ACLers return to the life they had before their injury with full confidence in their knee. Prior to that, he worked in the sports clinic at Hospital for Special Surgery, the #1 Orthopedic Hospital in the country. While there, he had the opportunity to hone his skills as an ACL specialist working closely with world-renowned surgeons and evaluating patients from all over the world. He completed his sports residency training at the University of Delaware where he had opportunities to work with many of their Division I sports teams as well as the Philadelphia 76’ers NBA G-league affiliate, the Delaware Blue Coats. He also trained at Champion Sports Medicine in Birmingham, Alabama where he had the opportunity to learn from researchers in the American Sports Medicine Institute. Currently, Tommy works exclusively with ACLers through his digital coaching model. While many of these clients are athletes, Tommy works with ACLers of all different abilities helping them to build the strength they need to overcome this unique injury. One of his favorite aspects of his job is taking active clients who have never been a “gym person” before and showing them the amazing things that happen when they learn to strength train.

Disclaimer – The content here is designed for information & education purposes only and is not intended for medical advice.