Knee

ACL (Anterior Cruciate Ligament) Injuries and Reconstruction

Anatomy

The knee is the largest joint in your body and one of the most complex. Three bones meet to form the knee joint: the thighbone (femur), shinbone (tibia), and kneecap (patella). The kneecap sits in front of the joint to provide some protection. Knee ligaments connect the thighbone to the lower leg. The four primary ligaments in the knee act like strong ropes, holding the bones together and keeping the knee stable.

• Collateral ligaments—Found on the inside (the medial collateral ligament or MCL) and on the outside (lateral collateral ligament or LCL) of the knee, these ligaments control the sideways motion of the knee and brace it against unusual movement.
• Cruciate ligaments—Found inside your knee joint, these ligaments cross each other to form an "X" with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the knee's front to back and rotational/twisting motion.
• Anterior cruciate ligament—Running diagonally in the middle of the knee, this ligament prevents the tibia from sliding out in front of the femur and provides rotational stability to the knee.

Description

One of the most common knee injuries is an ACL sprain or tear. Athletes who participate in high demand sports like soccer, football and basketball are more likely to injure their anterior cruciate ligaments. About half of all ACL injuries occur along with damage to other structures in the knee, such as articular cartilage, meniscus, or other knee ligamentsPCL Injuries and ReconstructionCollateral Ligament InjuriesCombined Knee Ligament Injuries. Most ACL injuries are complete or near complete tears, while partial tears are quite rare. If you have injured your ACL, you may require surgery to regain full function of your knee. This will depend on several factors, such as the severity of your injury and your activity level.

An injured ligament is considered a sprain, and is graded on following severity scale:

• Grade 1 sprain—The ligament is mildly damaged. It has been slightly stretched but is still able to help keep the knee joint stable.
• Grade 2 sprain—The ligament is stretched to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
• Grade 3 sprain—The ligament has been split into two pieces and the knee joint is unstable. This is commonly referred to as a complete tear of the ligament.

Symptoms

When injuring your ACL, you may hear a "popping" noise and feel your knee give out from under you. Within 24 hours most people experience swelling of the knee and many have pain as well. Other typical symptoms include: loss of full range of motion, tenderness along the joint line, and discomfort while walking. If ignored, the swelling and pain may resolve on its own, however, if you attempt to return to sports, your knee will probably be unstable and you risk causing further damage to the cushioning cartilage (meniscus) of your knee.

Causes

An ACL injury can occur in various ways, including: rapidly changing direction; stopping suddenly; slowing down while running; landing incorrectly after a jump; and direct contact or collision, such as a football tackle. In fact, 70-80% of ACL tears occur without a collision with another person/player. Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other suggested causes include differences in pelvis and lower extremity (leg) alignment, increased looseness in ligaments, and the effects of estrogen on ligament properties.

Diagnosis

Your physician will examine all the structures of your injured knee and compare them to your uninjured knee. Most ligament injuries can be diagnosed with a thorough physical examination.  X-rays can reveal any injury to the bone. However, it is possible for these images to appear normal. Another test which may help confirm your diagnosis include magnetic resonance imaging (MRI), which shows soft tissue and ligamentous structures to diagnose or confirm your diagnosis.

Nonsurgical Treatment

A torn ACL will not heal without surgery. However, nonsurgical treatment may be effective for patients who require a lower activity level which may allow them to recover to a quieter lifestyle without surgery. In the latter case, if the overall stability of the knee is intact, your doctor may recommend simple, nonsurgical options. Patients with a higher activity level, especially young athletes, often require surgical treatment to stabilize the knee and allow return to normal activity levels.

• Immobilization—Your doctor may apply a brace to keep your injured knee from moving. Crutches may also be recommended to prevent you from putting weight on your leg.
• Physical therapy—As the swelling goes down, a careful rehabilitation program will be started. Specific exercises will restore function to your knee and strengthen the leg muscles that support it.

Surgery

Older techniques consisted of sewing the torn ends of the ligament back together. This relatively simple operation did not work long term and the ligament usually tore again. The standard operation now reconstructs the ACL ligament with other tissue as replacement. The term for a piece of tissue that is transplanted surgically is called a graft. Autograft refers to your own tissue, allograft refers to tissue from a cadaver.  For the last several decades, ACL reconstruction with a graft has been the standard way of treating ACL injuries in young, active individuals.  Over the last decade, the importance of putting the new ACL graft in its correct (anatomic location) during ACL reconstruction has been better understood and it is very important that your surgeon be familiar with anatomic reconstructions to give the best outcomes. 

While ACL reconstruction has been around for decades and has a long track record of success there has always been interest in finding a way to get the native ACL to heal or to repair it directly rather than building a new ACL with a graft (ACL reconstruction).  As mentioned above, older techniques of sewing the ends of the ligament together had a high failure rate.  Recently, there is a new technique (BEAR) that shows promise that may be able to repair the ACL rather than reconstruct it. More information about BEAR can be found further down in this discussion. Regardless of the surgery type (repair versus reconstruction) ACL surgery is done arthroscopically. 

In our practice for ACL reconstruction there are 4 main choices for graft selection. Additionally, with the recent introduction of the BEAR technique, ACL repair may be an option for you.  You and Dr. Stewart will discuss ACL repair versus reconstruction and if ACL reconstruction is preferable, then you will discuss which graft is most appropriate for you and your goals.

1. Patellar Tendon Autograft

2. Quadriceps Tendon Autograft

3. Hamstring Tendon Autograft

4. Allograft

There are pros and cons to each. It should be noted that the most recent research shows similar outcomes, regardless of which type of replacement is used to build your new ACL. In fact, there are many current professional and collegiate athletes who have continued to be competitive after ACL surgery with any of the above. The final decision for which graft type is a matter of personal preference.

Patellar Tendon Autograft: This graft has been used for years because it provides a strong replacement for the ACL and can be securely fastened in place in the knee because of the bone graft. This technique uses the middle third of the patellar tendon along with a bone plug from the tibia (shin) and the patella (kneecap). This is still considered the “gold standard” by which all grafts are compared.  It has the lowest document retear risk of all of the grafts in young competitive athletes. However, use of this graft has a higher chance of side effects consisting primarily of pain, inflammation, and/or tendinitis in the region of the patella and the patellar tendon. This is particularly a problem in those that need to kneel or crawl such as wrestlers or carpenters.

Quadriceps Tendon Autograft: This graft option has recently gained exposure although it is a technique that has been used for years. The middle third of the quadriceps tendon with or without a bone plug from the upper end of the patella (kneecap) is used. The advantage to this graft is consistency in size. Due to the original size of the tendon, surgeons can harvest the appropriate size graft every time. It also does not cause the kneeling pain that some patients develop with the patellar tendon autograft. In most studies, retear risk with this graft appears similar to patella tendon autograft.

Hamstring Tendon Autograft: Provides a graft that is just as strong, and the newer fixation methods are at least as strong as those for the patellar tendon. The two hamstring tendons sometimes re-grow; however, when they do not, the remaining three hamstrings get stronger to compensate for their loss. Most people do not notice any significant strength weakness after removal of these two hamstrings, but athletes in sports such as gymnastics, sprinting, or ballet dancing may notice some weakness of knee flexion. There may be a somewhat higher retear rate for hamstring tendon autograft in young competitive athletes. There is a smaller scar with hamstring autograft compared to the other autografts.

Allograft: The use of donor tendons (allograft) is the final choice. Using the donor tendons is advantageous because there is less trauma to the patient’s leg because we do not have to remove any tendons to place them in the knee. Thus, there is less pain after the surgery and the early phases of the rehabilitation progress more quickly. Also, we can obtain as large a tendon as we need. When we take tendons from one area of the body to use in another, we are limited by how much the body has to spare. Essentially, we are “robbing Peter to pay Paul.” In small individuals with small tendons, there may not be enough to spare. Note that using the allograft does not accelerate your return to sports, as the maturation process that every graft must undergo is actually slower with the donor graft. There are some risks with the donor graft that the other grafts do not have. Specifically, it is theoretically possible that infection could be transmitted by the graft. The grafts are thoroughly tested, but it is possible that HIV or hepatitis could be transmitted through the graft. A few cases of HIV transmission occurred in approximately 1990 and none have been reported since. At about that time, the testing methods improved significantly. The risks are less than those with blood transfusion and the most recent figures indicate that the risk of HIV is less than 1 out of 2.5 million. Thus, while it is theoretically possible that HIV could be transmitted by the graft, it is extremely unlikely.

The postoperative rehabilitation is similar regardless of the graft chosen. Allografts are less painful compared to the hamstrings and less pain with the hamstrings compared to the patellar/quad tendon. However, usually after a few weeks, this all equalizes. Each graft has an excellent track record and in truth the differences between them is quite small. Regardless of the graft that we choose, you have a 90% or better chance of getting back to your desired activities.

The BEAR (Bridge-Enhanced ACL Repair) implant is a novel first technology to clinically demonstrate the ability to heal the torn Anterior Cruciate Ligament (ACL) and restore its original orientation and anatomy. This presents a potentially significant improvement, because until now the torn ACL would have been treated with a procedure called ACL reconstruction. As discussed above, during ACL reconstruction the surgeon removes the torn ACL and replaces it with a tendon graft harvested from another part of the leg (called autograft) or uses a tendon graft from a deceased donor (called allograft). Although ACL reconstruction is effective, this procedure has some drawbacks. Using an autograft from your own body is associated with a more invasive procedure and can leave your body with sometimes permanent deficits. Using allograft can be associated with increased re-tear rates in young, active individuals. Furthermore, ACL reconstruction does not completely restore normal ACL anatomy and joint mechanics and some people are not able to return to the same level of activities after ACL reconstruction. In addition, ACL tears are associated with a higher risk for development of osteoarthritis.

The BEAR implant is different because it works with your own blood to heal the torn ends of your ACL back together. BEAR is supported by high quality scientific data and 15+ years of research. It enables the restoration of patient’s own ACL to its anatomic orientation with the potential for more normal joint mechanics. By preserving the native ligament, this technique helps to preserve important mechanoreceptors contained in the native ACL which are otherwise lost when the ligament is removed during reconstruction of the ACL with a tendon graft.

Due to its groundbreaking nature, the BEAR implant has received special DeNovo clearance by the U.S. Food and Drug Administration and is indicated for skeletally mature patients at least 14 years of age with a complete ACL rupture, as confirmed by MRI. Patients must have an ACL stump attached to the tibia to allow for the restoration of the ACL and the implantation must be performed within 50 days from the original injury. BEAR has been shown to be effective across a broad range of tear types (Type 1 through Type 4).

However, we do not have long term data on this.  In addition, in preliminary studies it does appear to have a higher retear rate for young competitive athletes than ACL reconstruction.  Because of this, ACL reconstruction has been and continues to be the most common treatment option for ACL tears in young active athletes. For patients that understand the pros and cons and desire an option that avoids cadaver grafts and does not sacrifice any of their other tendons (hamstring, patella tendon or quadriceps), BEAR is an option.  BEAR shows promise and does offer some potential benefits for treating ACL injuries compared to ACL reconstruction.

Potential Advantages of BEAR include:

• Restores native ACL and orientation
• Preservation of ACL mechanoreceptors with potential for more normal joint mechanics
• Superior hamstring strength (compared to hamstring autograft ACL reconstruction)
• Superior Knee function scores (KOOS)
• No permanent donor site deficits/symptoms
• Reduced invasiveness compared to autograft
• Avoidance of potential allograft/donor tissue complications
• Potential for decreased post-traumatic osteoarthritis
• Revisions easier than a revised ACLR

Potential Disadvantages of BEAR include:

• Reported higher retear rate in the first two years when compared to autograft reconstruction in young athletes
• New, which means we lack long term outcomes to know how it does over time
• More restricted activity and rehab program for the first several months after surgery compared to ACL reconstruction

BEAR Implant 

VIDEO: Dr. Stewart talking about doing the BEAR Implant at Holland Hospital

Recovery

Whether your treatment involves surgery or not, rehabilitation plays a vital role in helping you regain knee strength and motion, and getting you back to normal activities. If you undergo surgery, your physical therapy will first focus on returning motion to the joint and surrounding muscles. This will be followed by a strengthening program designed to protect the new ligament by gradually increasing stress. The final phase of rehabilitation is aimed at a functional return tailored to your sport.

VIDEO: Injuries to the Anterior Cruciate Ligament (ACL) - Dr. Stewart - Holland Hospital Medical Minute

VIDEO: Dr. Bruce Stewart ACL injuries Part 1: An Introduction to the ACL

VIDEO: Dr. Bruce Stewart ACL injuries Part 2: Treatment Options

VIDEO: Dr. Bruce Stewart ACL injuries Part 3: Graft Choices

VIDEO: Dr. Bruce Stewart ACL injuries Part 4: What to Expect with ACL Reconstruction

VIDEO: Dr. Bruce Stewart ACL Reconstruction Using Patella Tendon Autograft - Surgical Footage w/Explanation

VIDEO: Dr. Bruce Stewart ACL Reconstruction Using Hamstring Tendon Autograft - Surgical Footage w/Explanation

VIDEO:Dr. Bruce Stewart Knee Injuries in Athletes, Holland Hospital Physician Lecture Series, May 2015