The anterior cruciate ligament, or ACL, is the most important ligament of the knee to prevent the knee from sliding forward or rotating anterolaterally. Patients who sustain an ACL tear often have problems with twisting and turning activities, such as in playing football, soccer, or skiing, and will often require an ACL reconstruction to provide stability to their knee.
In addition to its stability role in the knee, the ACL also provides protection for the menisci of the knee. When the knee continues to have instability episodes, it is not uncommon to have either the medial or lateral meniscus tear. However, when menisci tear there is much higher risk of the development of osteoarthritis. Because of this, Dr. Savadekar usually recommends ACL surgery and that an ACL reconstruction be performed in young or otherwise active patients and in almost all patients who report instability with twisting or turning activities.
ACL reconstruction is a commonly performed surgical procedure and with recent advances in arthroscopic surgery can now be performed with minimal incision and low complication rates.
An ACL surgery requires precise knowledge of the anatomy of the knee, attachment sites of the ACL and knowledge on the other ligaments and structures of the knee. If one fails to replace an anterior cruciate ligament at its correct attachment sites or if other concurrent injuries are not treated, there is a much higher risk of failure of the ACL graft. Therefore, it is advisable to get the surgery done from a specialist knee surgeon with expertise in arthroscopic surgery.
While there are two bundles of the ACL, the anteromedial and posterolateral bundles, there is still controversy as to whether both should be reconstructed as a single ligament or as two separate ligament grafts. While the double-bundle ACL reconstruction technique appeared very promising initially, many research groups, have significantly narrowed the indications for double-bundle ACL surgery and found there is very little difference between a single and double-bundle ACL reconstruction for the vast majority of patients.
The most important technical issue is to have the ACL reconstruction graft placed in the correct position. On the tibia (shinbone), the tunnels should be in line with the posterior margin of the anterior horn of the lateral meniscus. On the femur (thigh bone), the reconstruction tunnel should be placed at the midpoint of the attachment bundles of the anteromedial and posterolateral bundles, with the main portion of the reconstruction tunnel being posterior to the lateral intercondylar ridge (resident’s ridge).
A large number of ACL reconstruction graft failures are in those patients who have the graft placed in the incorrect position (non-anatomic) which leads to either stretching of the reconstruction graft or failure to control knee rotational laxity.
The technique of ACL reconstructions has changed dramatically over the last decade in orthopaedics. ACL reconstruction grafts performed prior to 5-10 years ago were usually placed more centrally on both the tibia and femur and many of these patients have continued problems with rotation instability. This problem became recognized through extensive clinical and biomechanical research and the surgical technique has currently changed dramatically to where the reconstruction tunnels are now placed more anatomically to provide better stability to the knee.
Dr. Savadekar’s primary surgical reconstruction technique involves using hamstring tendon autograft (from the patient’s own tissues) during ACL surgery. The reconstruction tunnel is drilled at the anatomic attachment site of the ACL on the tibia and a closed socket tunnel is drilled at the anatomic attachment site on the femur. The patellar tendon graft is pulled into the joint and fixed in place with titanium button loop on femoral side and interference screw on tibial side. Dr. Savadekar utilizes single incision for graft harvesting as well as for passing the graft in the tunnels. The utilization of fewer incisions results in less pain post-operatively for the patient, while the use of the autograft allows the patient to return to activities sooner with a lesser risk of reconstruction graft failure.
It is absolutely essential for a physiotherapist to be consulted and to work with physiotherapist post-operatively following ACL surgery. Reactivation of the quadriceps mechanism, edema control, patella mobilization, maintenance of full knee extension and regaining knee motion are absolutely essential to obtaining optimal post-operative outcomes. It is also imperative follow up with Dr. Savadekar regularly for assessment of the recovery.
ACL reconstruction surgery consists of replacing a torn ACL with another ligament or tendon. This can be from one’s own body (an autograft) or from a donor (an allograft). Allograft can be chosen from various options like hamstring tendon, quadriceps tendon, bone patellar-tendon bone, peroneal tendon depending on surgeon’s choice. In an ACL surgery, tunnels are reamed at the normal attachment site of the ACL on both the femur and tibia and the graft is secured either inside or outside these tunnels. There are multiple ways to secure the graft, and this can include fixation within the tunnels with metal or bioabsorbable/plastic screws or through a loop and button placed on the outside of the tunnels.
The only time that ACLs can be repaired is when an ACL is torn with a piece of bone, usually off the tibia, which is much more common than when torn off the femur. In this circumstance, if there is not a lot of intrasubstance stretch within the torn ACL, the bony can be refixed at its normal attachment site and secured such that early motion can be started. In those instances where the tissue is not strong enough to allow early motion, there is a much higher risk of stiffness if immobilization is required after surgery.
In terms of a repair of the ACL, there are perhaps 10% of patients who may have injury only to the attachment site on the femur or tibia and sutures can possibly be placed in to do a repair. In those circumstances, research is still ongoing to try to improve outcomes because attempts at repairs in the literature previously have not shown good outcomes over time.
One of the most important things for preventing a retear of an ACL reconstruction is to ensure that the patient has gone through the proper recovery phase after surgery. In the past, many surgeons tried to get their patients back to full activities by 5 or 6 months. However, more recent data has suggested that waiting up to 9 months may be more advantageous in that the rate of retear goes down significantly after the 9-month timeframe for a return to activities after ACL surgery. In general, it is important to make sure that an athlete has a full return of proprioception, strength, agility, and endurance to minimize their risk of reinjury.
The ability to return to running after an ACL surgery is dependent upon many factors. If the surgery is only the ACL, and there are no other ligaments or meniscus tears treated, and the cartilage surfaces are intact, then one has to go through a proper rehabilitation program first. In general, we feel that an athlete has to wait a minimum of 4 months after their ACL reconstruction return to running. Additionally, they should have appropriate quadriceps strength. In these circumstances, if the patient has a good return of function, good motion, and does not have a valgus collapse when performing a single-leg squat, they are generally able to initiate a return to their running program at about the 4-month timeframe. This allows the quadriceps mechanism to be strong enough to prevent extra stress on the knee which can lead to knee swelling (effusions) and possibly damage the cartilage which would not be noticed until several years later.
The number one cause of ACL reconstruction failure in all of the literature is improperly placed ACL grafts at the initial surgery. This can cause extra stress on an ACL reconstruction graft which can lead to its failure. In addition, a missed other ligament problem at th time of the ACL surgery, such as an MCL or a posterolateral corner injury, can also put significant stress on an ACL reconstruction graft, which can lead to its failure. Other factors that can cause an ACL graft to fail can include the lack of the posterior horn of the medial meniscus.
The other important cause of failure is non-compliance of the patient to rehabilitation protocol.
ACL reconstruction by itself does not lead to the need for a total knee replacement. However, when one does have a knee injury, especially when one loses their meniscus tissue, they are at a higher rate for the development of osteoarthritis.
A BTB ACL reconstruction is one that uses a patellar tendon graft. It is called a “BTB” graft because it takes bone off the patella, uses a strip of tendon, and then takes a piece of bone off the tibia. This graft has been documented in animal models to be the one that heals the fastest, with most bone plugs healing in their tunnels at around six weeks after surgery.
A double-bundle ACL reconstruction is one that uses two separate grafts to reconstruct the anteromedial and posterolateral bundles of the anterior cruciate ligament. Double-bundle ACL reconstructions were very popular about a decade ago, but clinical studies and biomechanical studies have not shown a great deal of difference between placing one graft in the center of the ACL attachment sites in the femur and tibia versus placing two grafts at the different attachment sites of these bundles on the femur and tibia.
The ACL is important to prevent rotation of the tibia on the femur. In particular, anterolateral rotation, which can occur with twisting and pivoting activities, occurs after an ACL tear. In addition, the tibia tends to slip forward on the femur when one is ACL deficient. This particularly can be a problem for the posterior horn of the medial meniscus because it sees extra stress and can tear. ACL reconstructions that are performed in patients who note instability, but also in younger patients who may participate in twisting, turning, and pivoting sports to ensure that they do not tear their meniscus and develop osteoarthritis later in their lives.
A partial ACL tear can involve one of the bundles of the ACL alone. In particular, if the posterolateral bundle of the ACL tears and the patient notices difficulties with twisting, turning, and pivoting activities, then a single-bundle posterolateral bundle reconstruction of the ACL may be indicated. In these circumstances, if the anteromedial bundle is still pretty much intact, it would be recommended not to take it out and perform a complete reconstruction, but rather to perform a single bundle reconstruction (partial reconstruction) to address the problems with twisting, turning, and pivoting.
For those who have a first-time ACL reconstruction using a standard graft, patients are usually allowed to walk with full weightbearing as soon as their surgical blocks wear off after surgery. In general, they can then proceed to weaning off of crutches when they can walk without a limp. Most of the patients are able to wean off of crutches at about the 2-week point after surgery. However, some patients may take longer to wean off of crutches and should not use the timeframe exclusively, and should ensure that they are not limping before they completely discontinue the use of crutches.
Returning back to work after an ACL reconstruction is a very individualized decision. In those people who have desk jobs, they can often return back to work for partial work days within 7 to 10 days, as long as they can ice and elevate their knee if there is any risk of swelling. For those patients who require the use of ladders, stairs, twisting or turning, or lifting patients, the time can vary from 4 to 7 months after surgery, depending upon the type of graft, associated other surgeries with the ACL reconstruction, and their ability to have their overall strength and endurance return.
The use of an internal brace utilizes a surgical tape to try to augment an ACL reconstruction graft. To date, there are few studies that can determine whether this helps ACL reconstruction graft healing or not.
Almost all patients develop some numbness after an ACL reconstruction procedure. This is because the nerves from the saphenous nerve, especially the infrapatellar branch of the saphenous nerve, cross from the inside over the top to the outside of the knee. These nerves are so tiny that they can hardly be appreciated by open eyes, so are difficult to salvage. Patients with patellar tendon graft incisions and most hamstring incisions therefore will develop some numbness over the front of their knee. In addition, patients who may have meniscus repairs to either the medial or lateral meniscus will also develop numbness to some extent around the surgical incisions. But this will not hamper the knee function.
In general, the decision about what type of anesthesia one has for their ACL reconstruction should be made with an anesthesiologist. As orthopaedic surgeons, we can usually work with an epidural, spinal, or some type of general anesthesia. It is difficult to perform ACL reconstruction grafts under local anesthesia, because the assessment of meniscus tears and the positions that the knee has to be bent into can be compromised if the patient is guarding. It may not allow for all pathologies to be diagnosed and treated appropriately.