ACL tears are a common ligamentous injury. They are also one of my favorite injuries to treat!
While I may get excited about ACL tears, understandably most patients (about 1/3000 Americans)5 do not. It can be a devastating injury, and you will have your work cut out for you throughout the rehab process.
There are two approaches someone with an ACL tear can take: non-operative and operative. Deciding which is best for you will depend on a multitude of personal and physiological factors. Your physician will be able to help you decide.
Let’s fast forward and assume you’ve opted for ACL reconstruction surgery. As if this wasn’t overwhelming enough, now you’re coming face to face with cost, estimated recovery time, and “you’re going to be drilling into what?!”.
Add choosing a graft type to the mix and now your head is really spinning.
There are a variety of grafts that can be used to create your new ACL. Let’s look closer at what those are, the benefits and drawbacks of each and where current research stands on the topic.
Autografts are grafts that are harvested from your own body. They are the most common form of graft used in ACL reconstruction.
During your surgery, your surgeon will begin by taking out a piece of an existing tendon to create your new ACL. These autografts are actually stronger than your native ACL. Studies show they are capable of sustaining a higher load before rupturing.1
There are 3 different sites used for harvesting these grafts: the patellar tendon, hamstring tendon,
The patellar tendon connects your patella to your tibia and is a very common choice when choosing a graft tendon. This tendon connects bone to bone just like the ACL, making it a great graft choice. The middle 1/3rd of the patellar tendon is used when creating a new graft and is easy to harvest.3
The patellar tendon is a very strong graft, making it a popular choice among surgeons. Studies have found this graft generally demonstrates less laxity than the hamstring graft.2
When compared to other graft choices, the bone plugs on each end of the patellar tendon provide faster bone to bone healing (6 weeks).1,3 As a result, surgeons usually use this graft for patients with short-term, high functioning demand such as athletes.2
The biggest downside to the patellar tendon graft is the heightened risk of post-operative complications (i.e. patellar fracture, weakening of quadriceps, patellar tendon rupture, patellar tendonitis, anterior knee pain2, knee extension loss, osteoarthritis).1,2,3,5
Pain in the front of the knee is the most common complaint I get from patients with a patellar tendon graft and has been known to occur in 5-55% of cases.2 This makes use of a patellar tendon graft contraindicated for patients whose job or hobbies require frequent kneeling.2
Hamstring grafts are another very common graft choice. The grafts are taken from the back of your thigh using either one hamstring muscle (semitendinosus) or two hamstring muscles (semitendinosus and gracilis).
From these tendons, a double-strand or quadruple strand graft is formed. The quadruple strand graft has been shown to provide more stability than the double strand in ACL reconstruction.5
Hamstring grafts are associated with less pain both immediately post-operative and longterm.5 Choosing a hamstring graft with not cause lasting anterior knee pain or pain with kneeling.
The main downside to hamstring tendon graft is the increased likelihood of retear. The hamstring graft has been found to have a higher failure rate when compared to the patellar tendon graft.4,6,7 This would make sense, as the hamstring graft has been shown to not be as strong as the patellar tendon graft.2
Another downside to the hamstring graft is a longer healing time due to the lack of bone plugs.2 This results in longer bone integration time when compared to the patellar tendon graft.
Following hamstring tendon harvest some patients have demonstrated decreased bending strength at the knee. Although research has found this usually dissipates a year after surgery2, it is an important note to make.
The hamstring works with the ACL to provide stability to the knee.
Within the first year!5
The quadriceps tendon is not used as commonly as the hamstring and patellar tendons. This, of course, means it has been studied far less.
This may be one of the biggest pitfalls of the quadricep tendon- lack of long-term follow up.2
About only 1% of surgeons consider even consider using it.1 However, those that due report it is even easier to harvest than the patellar tendon graft.1
Early outcomes regarding the use of the quadriceps tendon are promising, showing strength and stability similar to the patellar tendon graft without the accompanying knee pain.2
The best of both worlds!
I hope to see more long-term studies regarding quadriceps tendon grafting in the future so we can have more definitive data. Until then, know it is an option, but not a common one.
An allograft is a graft that is harvested from a cadaver instead of your body. There are many different cadaver sites used for ACL reconstruction (patellar tendon, hamstring, tibialis posterior/anterior and Achilles tendon).3 While these types of grafts are still less common than autografts, they are slowly growing in popularity.3
A huge upside to using an allograft is an obvious one. No harvesting is done on your own body! This decreases post-operative pain and the complications that come with removing tissue from another area of your body.1,2,3,5
Unfortunately, allografts still come with their own set of risks.
Since this tissue is from another person, there is a possibility of disease transmission. While the sterilization process that these grafts go through does decrease that risk, it actually delays the remodeling and integration of the graft which increases the risk of graft failure.1,2 These sterilization techniques also increase
A well-accepted consensus remains that this type of graft choice should be avoided in young and/ or active populations due to the increased risk of rupture.1,5
When introducing a foreign tissue into your body you run the risk of it being rejected. This is absolutely true for allografts as well. If your immune system rejects the donor graft it will not integrate into the bones as hoped.1,2
Allografts are also more expensive than autografts. However, there is mixed evidence regarding the TOTAL cost of ACL reconstruction using an allograft vs autograft.
With an autograft, time in the operating room is decreased because there is no additional harvesting time. Research has not been consistent enough to determine is this decreased OR time is enough to offset the higher price tag of the cadaver graft or not.1,5
Synthetic grafts are occasionally used in ACL reconstruction. These are grafts created from synthetic materials in an effort to provide the same physiological function as the ACL. Materials that have been used in the past include carbon fibers, Gore-Tex, Dacron Trevira, Leeds-Keio, and polypropylene.5
There are not many longterm studies available for synthetic grafts, as early outcomes were not great.1 One study even found that out of 51 patients with synthetic grafts, 14 of them had failed within 19 years.8
A key issue with synthetic grafts is their tendency to elongate over time. This leads to increased laxity in the graft and eventually early breakage.3 The search for a synthetic material that avoids this stretching phenomenon continues.
Typically the only time a synthetic graft should be considered is it the patient is motivated, over 40 years old, symptomatic and in need of a quick recovery.2 Surgeons will also use a synthetic graft in the event that someone is wanting to return to activity for a once in a lifetime event.2 This may be one reason why the synthetic graft is gaining popularity in the sports world5, but the evidence just doesn’t support this choice for long-term benefit.
Alright, you’ve met your graft choices. Still feeling overwhelmed? Let’s summarize.
Short-term: Allografts and synthetic grafts are going to be less painful than an autograft simply because there is no harvesting from your own body.
Long-term: A synthetic, hamstring or allograft is generally going to leave you with less residual pain, specifically anterior knee pain and pain with kneeling. Patellar tendon grafts are associated with more long-term pain.
The patellar tendon provides the greatest tensile strength. It has superior bone integration due to the presence of bone plugs at each end that no other option has.
A synthetic or allograft is going to result in the shortest recovery time in regard to pain. However, the total rehab progression will need to be taken slower due to decreased graft strength and increased time needed for integration. A hamstring tendon graft usually requires the longest recovery time due to donor site injury along with the time needed for bone integration.
Patellar tendon grafts tend to produce the most muscular weakness (primarily of the quadriceps muscles). Hamstring grafts can cause weakness of the hamstring, but this usually resolves in the first year after surgery.
Return to Sport Potential
Both hamstring and patellar tendon grafts have a good return to sport/ prior activity likelihood. No significant differences have been noted between the two.
Chance of Rupture
The patellar tendon graft may have a lower risk of rupture when compared to a hamstring graft, but the evidence is inconsistent.
The risk of rupture is higher in synthetic and allografts used for younger patients and those who are more physically active.
Autografts are cheaper than allografts. The decreased time required in the operating room for an allograft may offset the cost, but the
Choosing the best graft for you will be a decision you and your surgeon need to make together based on your age, functional demands
Basically, the patellar tendon is strong but comes with a higher risk of post-op complications.
The hamstring graft isn’t quite as strong but has fewer associated donor site impairments.
The quadriceps tendon is a promising graft choice, possibly combining the strength or the patellar tendon and low morbidity of the hamstring. However, there isn’t much long-term evidence surrounding its use yet.
Allografts and synthetic grafts appear to have a higher failure rate but may be appropriate for specific populations, particularly those who need a shorter recovery time.
While there is still no “perfect” graft, I do have some good news for you. Studies have found that the percentage of patient satisfaction with graft choice is similar among all groups.5 Therefore, odds are that whichever graft you end up choosing, you’re going to be happy with the decision.
Now that you and your surgeon have chosen the perfect graft, make sure your rehab is up to par! If you’re in the Portland, OR area come work with me!
1. Castelli A, Perelli S, Ferranti E, Jannelli E, Zanon G, Benazzo F. Graft Choices in ACL Reconstruction | International Congress for Joint Reconstruction. https://icjr.net/articles/graft-choices-in-acl-reconstruction. Accessed October 22, 2019.
2.Cerulli G, Placella G, Sebastiani E, Tei MM, Speziali A, Manfreda F. ACL Reconstruction: Choosing the Graft. Joints. 2013;1(1):18-24.
5.Macaulay AA, Perfetti DC, Levine WN. Anterior Cruciate Ligament Graft Choices. Sports Health. 2012;4(1):63-68.
6.Persson A, Fjeldsgaard K, Gjertsen J-E, et al. Increased risk of revision with hamstring tendon grafts compared with patellar tendon grafts after anterior cruciate ligament reconstruction: a study of 12,643 patients from the Norwegian Cruciate Ligament Registry, 2004-2012. Am J Sports Med. 2014;42(2):285-291.
8.Ventura A, Terzaghi C, Legnani C, Borgo E, Albisetti W. Synthetic grafts for anterior cruciate ligament rupture: