What is the ACL and what does it do?
§ The anterior cruciate ligament (ACL) connects the femur bone to the tibia bone in the center of the knee joint. (Ligaments connect bones to bones)
§ When athletes “blow out” their knees – this is the ligament that is commonly torn.
§ The ACL is important during daily activities but absolutely critical to the stability of the knee during sports.
What is the native anatomy of the ACL?
- The ACL is made up of two functional bundles of tissue, the anteromedial (AM) and posterolateral (PL) bundles. These bundles are first seen during fetal development and persist throughout life.
§ The AM bundle of the ACL primarily controls anterior (forward) movement of the tibia underneath the femur, and the PL bundle controls rotational stability of the knee, such as in pivoting, twisting, running, and jumping. [9,10]
- In other words, each bundle has a different function, and this is reflected in the anatomy. When the knee is straight the AM and PL bundles are parallel. As the knee is flexed, the two bundles cross each other
Are ACL tears common?
§ ACL tears are very common. The highest occurrence (incidence) is in individuals between 15 to 25 years of age, who participate in pivoting sports (like soccer and football). However, ACL tears can occur at all ages and in all sporting activities.
How is an ACL tear diagnosed?
- Tear of the ACL can be diagnosed by a history of trauma to the knee (contact or non-contact) and physical examination. MRI scan can confirm the diagnosis
Is surgery absolutely necessary for my ACL tear?
§ No. There are some patients who are able to function without an intact ACL. These patients modify their activity, by eliminating pivoting and cutting movements and sports, in order to minimize subluxation, or “giving away” episodes. However, sometimes during regular activities the ACL-deficient knee can buckle or “give way” (subluxate) resulting in painful episodes with swelling.
§ Importantly, there is a risk for damage to the menisci (cartilage shock absorbers) and articular coating cartilage inside the knee joint with each subluxation event. This damage can lead to degenerative arthritis.
§ Because of these concerns, a majority of active patients elect to undergo ACL surgery when the ligament tears.
I just tore my ACL—when will I be ready for surgery?
§ In general, there are three criteria that must be met before the ACL can be surgically reconstructed:
1) Swelling in the knee must go down to near-normal
2) Range-of-motion (flexion and extension) of the injured knee must be nearly equal to the uninjured knee
3) Good Quadriceps muscle control must be present (able to do a straight-leg raise)
§ Usually it takes a couple of weeks after injury before ACL reconstruction can be performed.
§ The presence of any associated injuries to the knee joint involving cartilage, meniscus, or other ligaments may change the time-frame for surgery.
What surgical techniques are used for ACL reconstruction?
- A standard technique of ACL surgery during a “single bundle” reconstruction involves removing a piece of bone and cartilage. This is called a “notchplasty.” A drill guide is then used to drill a single tunnel on both the tibia and femur. A single ACL graft is then passed through the tunnels
What are the goals of anatomic ACL reconstruction?
§ To restore 80-90% of native ACL anatomy
§ To maintain a long term knee health
Do we perform anatomic single bundle ACL reconstruction?
§ Yes – we perform single bundle ACL reconstruction in approximately 30% of our patients.
§ There are a few scenarios where we prefer to perform single bundle surgery:
- Patient has a very small native ACL insertion site. This typically can only determined at the time of surgery
- Patient is still growing and his or her growth plate is not closed
- Patient has severe arthritis
- Patient with multiple knee ligament injuries or knee dislocation
- Severe bone bruising and narrow intercondylar notch
- Patients who cannot wait 9-12 months to return to sports
- Professional or highly competitive athletes
Is anatomic single-bundle ACL reconstruction technique the same as had been performed years ago?
§ No, we have learned a great deal from our development of the double-bundle technique. We use these principles to perform a “Matched Anatomic Single Bundle” ACL reconstruction.
§ We carefully investigate the rupture pattern of the ACL and identify the native ACL insertion sites.
§ The tibial and femoral bone tunnels are then drilled in a matched anatomic fashion. (See pictures below)
- Previous single bundle techniques often utilized a PL to High AM, which led to impingement of the graft. The AM to AM approach leads to a more anatomical reconstruction. Today, we prefer to use a more anatomical approach with 50% middle tibial insertion to 50% middle femoral insertion.
Is it possible to tear just one bundle?
§ Yes – this is rare but does happen
§ Clinically an isolated tear of the:
- AM bundle leads to anterior-posterior instability
- PL bundle leads to rotatory instability
§ In either case we save the intact bundle and “augment” the ACL with a single bundle reconstruction – either the AM or PL… whichever one is torn
Frequently Asked Questions:
Why bother with an “anatomic” or “double-bundle” reconstruction if it takes longer, with respect to operating time and time to return to sports?
This method of ACL reconstruction (anatomic) regardless of whether we do single (30%) or double bundle surgery is meant to reproduce YOUR OWN ACL, both in regard to ligament placement and ligament size. We believe that this more closely reproduces “your” native anatomy. The analogy is akin to a suit. Why wouldn’t you want a custom tailored hand-made suit versus “off the rack”… even if it takes longer to make?
What happens to the knee joint if anatomy is not restored?
This entire discussion is a “game of millimeters”. The answer to this should be considered in two stages: the short term and the long term.
In the short term – a well-placed ACL reconstruction allows good restraint to both AP and rotational stability. This “macro-stabilization” allows patients to feel stable both subjectively and objectively and is key to returning to sports at a high level.
In the long term – subtle or “micro” motion about the knee likely accounts for the increased incidence of early arthritis in the affected knee (in addition to the damage from the initial trauma to that knee). Because my bone and ligament anatomy is different from yours, the forces across my ACL will be different. Because of this variation, a ligament meant for me will not work as well for you. Although this may be close enough to reproduce the “macro-stability” mentioned above, this will not stabilize the micro-motion that occurs around the knee in the long term.
Again, this is a game of millimeters and also the subject of millions of dollars in research today. We have been and are continuing to study this in an effort to continue to improve both our methods and your outcomes – both short and long term.
What is the main advantage of a double-bundle reconstruction?
More precision in regards to the ACL reconstruction. You were born with 2 bundles, why would you want a reconstruction that only replaces one of them?
Do we do a double-bundle reconstruction in every patient with a torn ACL?
No, we don’t. We perform single bundle ACL surgery on 30% of patients. There are cases (taking the rest of the knee and patient into account) where single bundle is better: 1) too small of a knee to safely place two bundles (technical issue), 2) Open growth plates 3) severe arthritic changes, 4) multiple ligament surgery. Again, your ACL surgery should be what is best for YOU as a patient and this includes age, activity level, bony anatomy, size of knee, open vs. closed growth plates, etc….
Is allograft, donor tissue safe?
Long answer - Nothing is ever 100% safe. There are risks to allograft and they include a possible risk of disease transmission. The often quoted numbers include risk of HIV transmission which is 1 in 1.6 million and hepatitis C which is 1 in 421,000.
A recent survey of the AOSSM (sports academy) in 2006 showed that 86% of the surveyed surgeons use allografts – so they are very commonly used in the sports medicine world.
Short answer – Yes allograft is safe. Your risk of being struck by lightning is higher (73 people are struck and die each year from lightening!) than your risk of contracting disease from allograft tissue.
Is allograft, donor tissue durable?
Yes. Both autograft and allograft undergo a process of ligamentization whereby the body’s own tissue remodels the graft. During the remodeling phase, the graft itself becomes weaker before regaining its strength. However, the athlete feels great and so will want to be more aggressive with his/her knee. It is imperative not to return too soon as this puts “our” grafts in danger. The use of allograft does require a longer time for biological healing.
When can I go back to Sports?
Generally, jogging begins at 3-4 months after surgery. Sport specific training begins at 6 months. Return to competition is allowed at 9-12 months following surgery. Remember, returning earlier increases the chances of ACL re-rupture. Although you may feel fine otherwise, biologically, the ACL graft takes about 9 months to heal.
Is rehab any different after a double bundle reconstruction?
No. All aspects of rehab are the same for single and double bundle ACL surgery.
If I’ve already failed a previous ACL reconstruction, can I still do a double bundle ACL reconstruction on my knee?
Yes. In fact, if you’ve already failed single bundle ACL reconstruction, a double bundle reconstruction is a very good option since it provides more rotational stability.