Reconstruction of the Anterior Cruciate Ligament

Overview

An anterior cruciate ligament (ACL) injury is a rupture or sprain of the ACL, which is one of the strong bands of tissue that connects your thigh bone (femur) to your shinbone (tibia). ACL injuries are most prevalent in activities involving quick pauses or changes in direction, jumping, and landing, such as soccer, basketball, football, and downhill skiing.

When an ACL injury occurs, many patients hear or feel a "popping" sensation, extreme pain, difficulty to continue activity, and loss of range of motion in the knee. Your knee may swell, become unstable, and painful to bear weight on.

Treatment may involve rest and rehabilitation exercises to help you restore strength and stability, or surgery to repair the torn ligament followed by rehabilitation, depending on the degree of your ACL damage. A good training regimen can help lower the chances of an ACL injury.

Is ACL Injury Common?

ACL tears are a common type of knee injury. Every year, between 100,000 and 200,000 case occur in the United States. They are widespread among athletes, particularly those who participate in start-stop, abrupt changes in direction activities such as football, basketball, soccer, and volleyball. You're also more susceptible if you have a physically demanding job that demands climbing, pivoting, or jumping.

What are Knee Ligaments?

There are two main types of ligaments in your knee:

• Collateral ligaments: The two collateral ligaments function similarly to straps on each side of your knee. The medial collateral ligament (MCL) is located on the inside of the knee. It connects the femur (thigh bone) to the shin bone (tibia). On the outside of your knee lies the lateral collateral ligament (LCL). It links the femur to the calf bone (fibula). The collateral ligaments keep the knee from shifting too much side to side.
• Cruciate ligaments: The two cruciate ligaments are inside your knee joint and connect your femur to your tibia. They cross each other to create an X:

1. The anterior cruciate ligament (ACL). The anterior cruciate ligament (ACL) is located deep within the knee joint. It connects to the tibia in front and the femur in rear. It is commonly damaged, particularly in athletes. The ACL is the key structure for proprioception and prevents the tibia from slipping too far forward in relation to the femur. The anterior cruciate ligament is frequently damaged in sports such as football and skiing, typically as a result of severe twisting motions, quick stopping, or landing awkwardly. Because recovering from an ACL injury can take up to a year, prevention has become an essential aspect in sports training.
2. The posterior cruciate ligament (PCL). It is similarly located deep within the knee joint and connects to the rear of the tibia and the front of the femur. When the posterior cruciate ligament (PCL) is overstretched, it is injured and can rupture if enough force is applied. The PCL is one-fifth the length of the ACL but twice as strong. As a result, it is significantly more difficult to damage the PCL. The PCL prevents the tibia from shifting too far back in respect to the femur. An abrupt force through the top of the shin, a vehicle accident or fall, or hyperextending the knee are common causes of posterior cruciate ligament injury.

Anterior Cruciate Ligament Functions

ACL is composed of collagen (a protein that joins tissues in animals), connective tissue, and somewhat stretchy elastic fibers. It serves the following purposes:

• When the foot touches a surface, absorb the impact.
• Connect the thigh and lower leg bones.
• Maintain correct bone alignment.
• Avoid twisting or compressing the knee.
• Maintain knee joint stability.
• Prevent the knee from moving in any dangerous or abnormal directions.

Risk Factors For ACL Tear

While anybody may tear their ACL, various circumstances can increase one's risk:

1. Female gender. Female athletes have three times more ACL injuries than men athletes. While the specific cause is unknown, variations in muscular training, control, and strength are among the possibilities.
2. Participation in specific sports. Basketball, soccer, football, volleyball, downhill skiing, lacrosse, and tennis are among sports where ACL rupture are prevalent. These sports need frequent and abrupt braking, such as cutting, turning, or landing on one leg.
3. Previously torn ACL. The risk of re-ripping a previously repaired ACL is around 15% higher than the risk of tearing a normal ACL.  According to one study, the risk is greatest in the first year following the original injury. Once the first knee has been injured, the likelihood of an ACL rupture in the opposite knee increases.
4. Age. ACL tears are most frequent between the ages of 15 and 45, owing to a more active lifestyle and increased sports engagement.

Having a risk factor does not guarantee that a person will get an ACL injury over his or her lifetime.

Types of ACL Injuries

ACL injuries are classified as sprains and vary in severity.

Grade 1: The ligament has suffered some injury and has been slightly strained (ACL sprain), but it is still capable of keeping the knee joint stable.

Grade 2: The ACL is strained and becomes loose. This type of ACL damage is known as a partial tear of the ligament. It is quite rare.

Grade 3: The ACL has divided into two sections and the knee is unstable, resulting in a total ligament tear (full ACL tear).

ACL Injury Signs & Symptoms

Signs and symptoms of an ACL injury may include:

• There is a popping sound.
• They get the sensation that their knee has given way from under them.
• Feel sharp pain.
• Swelling is common, especially in the first 24 hours following an accident.
• You will be unable to play immediately following your injury.
• You will lose your complete range of motion.
• Tenderness in the joints
• Walking causes pain.

Causes of ACL Tears

An ACL injury is frequently sudden and occurs in both contact and non-contact sports. It frequently occurs as a sport trauma:

• When an athlete plants a foot and abruptly changes direction as a result of cutting or turning moves.
• When a person falls on one leg, as in a volleyball or basketball jump.
• When the knee is directly struck, especially if it is hyper-extended or slightly curved inward.
• During a sudden slowing or stopping of running, the ligament might hyperextend.
• Repetitive stress on the knee can cause the ligament to lose suppleness (like a stretched out rubber band).
• While the knee bends backwards or twists, as might happen following a fall or when landing a jump awkwardly.

Sports injuries are the most common causes of ACL tears, however, the ACL can be injured during any trauma, such as during a car accident, falling off a ladder, or missing a step on a staircase.

Diagnosis of ACL Injury

The patient's knee will be examined by a doctor, who will note any swelling, tenderness, pain sites, and range of motion. He or she may also undertake physical tests such as manipulating the afflicted knee (passive motion) or asking the patient to move the affected knee while putting weight on it.

Physical examination examinations designed specifically to determine the integrity of the ACL are especially useful when done on the opposite (healthy) knee for comparison. The Lachman's sign test is the most commonly used exam.

Lachman’s sign test:

This test is carried out with the subject lying on his or her back and the afflicted limb relaxed.

• The examiner supports the leg with one hand on the lower thigh and one hand on the upper calf.
• The doctor softly bends the knee to about 30 degrees and then pushes the calf forward and upward.

The test can also be done on the unaffected knee. If the injured knee has a greater range of motion than the other knee, the ACL has most likely ruptured.

Other tests may also be performed to further assess the ACL as well as nearby structures, such as the meniscus and the medial collateral ligament (MCL).

Medical Imaging:

Although many ACL tears may be identified without the use of diagnostic imaging, a doctor may request one or more diagnostic imaging tests to confirm the existence and severity of an ACL injury:

• X-ray. It allows doctors to see a person's bones. Because of the potential of bone fracture, a plain x-ray of the knee is required if an ACL tear is suspected.
• Magnetic resonance imaging (MRI). It offers a thorough image of the knee joint's ligaments, tendons, bones, and cartilage, including the ACL. An MRI of the knee is used to confirm the diagnosis, check for other knee problems, and plan for surgery.
• Ultrasound imaging. It creates an image of the knee by using high-frequency sound waves. Ultrasound may detect resolution of tendons and ligaments outside of the knee joint, but because the ACL is located deep within the joint, ultrasound cannot detect ACL tears.

Who Needs ACL Reconstruction?

The need for surgery is determined by the degree of the ACL injury and the patient's lifestyle. An ACL that has been fully torn cannot heal on its own. However, studies have shown that in some people with a partial rupture of the ACL, the ligament may recover without the need for surgery.

1. Partial and complete ACL tears:

A doctor will use two manual tests to identify whether a tear is partial or complete:

• Lachman test: The doctor will try to move the shin bone away from the thigh bone. If the ACL is ruptured but still intact, the bones will not move or will move just little.
• Pivot shift test: The patient lies on their back as the doctor elevates their leg and applies rotational pressure to the knee. If the bones do not move, the test is negative.

In individuals with only a partial tear, it may be advisable to postpone surgery and first examine if the ligament recovers without it.

2. Patient lifestyle:

People who have totally torn their ACL and have an active lifestyle, particularly competitive sports, will require surgery to return to their previous level of activity and avoid further damage. Nonsurgical therapy may help some older individuals or those whose lives do not include strenuous activity to return to normal habits even if their ACL is not intact.

Anyone who returns to full exercise with a totally damaged ACL will almost certainly have knee instability. They are significantly more prone to tear their meniscus while they are in. The meniscus is a cartilage pad that cushions the bones that come together at the knee joint. Each knee has two menisci: the medial meniscus on the inside and the lateral meniscus on the outside. A torn meniscus causes knee discomfort and, in some cases, edema and need a surgical repair. A damaged meniscus, on the other hand, increases a patient's chance of getting osteoarthritis of the knee later in life.

How is ACL Injury Treated?

Treatment for an ACL injury will differ based on the patient's specific needs. For example, a young athlete participating in agility sports will almost certainly need surgery to safely return to athletics. Individuals who are less active, typically elderly, may be able to return to a more relaxed lifestyle without surgery.

Nonsurgical Treatment:

Without surgery, an ACL tear will not heal. Nonsurgical therapy, on the other hand, may be useful in people who are old or have a very low activity level. If your knee's general stability is intact, your doctor may offer easy, nonsurgical options.

• Bracing. A brace may be recommended by your doctor to protect your knee against instability. You may be given crutches to prevent you from placing weight on your leg to further preserve your knee.
• Physical rehabilitation. As the edema subsides, a thorough rehabilitation program is initiated. Specific exercises can help you regain knee function and improve the leg muscles that support it.

ACL Reconstruction Surgery:

In most situations, a torn ACL cannot be repaired or reattached. ACL surgery generally entails a total reconstruction of the ligament. The current standard of treatment for surgically fixing a damaged ACL is called ACL reconstruction. Choosing the appropriate surgical approach for an ACL injury from the outset can have long-term consequences, therefore doing ACL surgery right the first time is crucial.

• ACL reconstruction surgery steps:

The reconstruction of the ACL involves a series of basic procedures, which may differ significantly from case to case:

1. The orthopedic surgeon creates ports of entry for the arthroscope and surgical equipment by making tiny incisions around the knee joint.
2. The arthroscope is inserted into the knee and a saline solution is delivered to increase the space surrounding the joint. This frees up space for surgical equipment such as the arthroscopic camera, which feeds footage to a display and allows the surgeon to look within the knee joint.
3. The surgeon then examines the components that surround the torn ACL, such as the meniscus and articular cartilage. The surgeon repairs any lesions in any of these soft tissues.
4. The graft will then be harvested (unless a donor allograft is used). A graft is made by cutting a segment of tendon from another region of the patient's body and attaching it at either end to bone plugs obtained from the patella and tibia. These plugs aid in the stabilization of the graft that will become the new ACL.
5. Using a flexible guide wire, the surgeon inserts the replacement ACL into the femur and tibia.
6. Screws are used to secure bone plugs. These plugs will eventually fuse with the surrounding bone.
7. To complete the process, the surgical instruments are withdrawn. 

ACL Reconstruction Vs ACL Repair

The current standard-of-care surgical therapy for ACL injuries is ACL reconstruction. In this technique, a graft, or portion of tissue, is often inserted in the knee through small incisions in a minimally invasive operation. The majority of ACL procedures at HSS are ACL reconstructions.

ACL repair is a more traditional procedure that involves stitching the damaged ACL tissue back together using stitches rather than reconstructing it with a graft. ACL restoration was performed at select facilities, notably Hospital for Special Surgery, in the 1970s, but was discontinued due to unacceptably high failure rates of up to 50%. ACL repair has been upgraded and can now be done in a less invasive manner.

Some surgeons believe that modern ACL repair procedures are safe and may result in a faster recovery than ACL reconstruction. However, evidence on outcomes is limited, and failure rates for ACL repair appear to be 5 to 10 times greater in persons of all ages than for ACL reconstruction.

When ACL surgery fails, physicians must perform a revision surgery (a second procedure) to address any issues that were not addressed effectively the first time. If a repaired ACL fails, only an ACL reconstruction can be used to correct it. Having to redo any type of ACL surgery may result in a greater failure rate, a poorer rate of successful return to sports participation, and an increased chance of developing knee osteoarthritis.

It is critical for patients of all ages to have a good first surgery, but it is especially critical for young athletes. A failed operation can be terrible for them: In the short term, this might entail years away from their preferred sport. It can lead to persistent pain and loss of knee function in the long-term. 

Complications of ACL Reconstruction

1. Infection. Infection is uncommon, although it is always a possibility with any sort of surgery.
2. Stiffness. Knee stiffness is typical after surgery, but physical therapy can help. This may be prevented by conducting therapy prior to surgery to restore all of your motion.
3. Viral transmission. Receiving a cadaver graft always carries the danger of developing diseases such as HIV and Hepatitis C. You have a one in a million chance of receiving an HIV-infected graft.
4. The blood clots. A blood clot can be fatal, although it is uncommon. The clot may break off in the circulation and cause a pulmonary embolism or a stroke in the lungs or brain.
5. Kneecap discomfort. This is a typical problem when utilizing patellar tendon transplants.
6. Injury to the growth plate. This is a risk of early ACL repair in a kid or adolescent. If feasible, the surgeon will postpone the treatment until the skeleton has fully developed or will use specific procedures to prevent harming the growth plate.

Follow-up Care & Rehabilitation

Rehabilitation is critical for healing after an ACL damage in children or teens. Physical therapy will assist you in regaining knee and leg strength and motion.

If you have had surgery, rehabilitation will begin with returning motion to the knee and leg muscles. You will next go through a strengthening program designed to protect the new ligament by progressively increasing stress on it. Finally, your will take part in a personalized program that will optimize your return to a chosen sport.

It takes time for the ACL to heal. It is critical that you have realistic expectations regarding your rehabilitation. An athlete may not be able to return to sports for six months or longer following surgery, depending on strength and agility training.

Conclusion

ACL reconstruction is surgery to repair a damaged anterior cruciate ligament – a main ligament in your knee. ACL injuries are most prevalent in sports that require quick stops and changes of direction, such as soccer, football, basketball, and volleyball.

Ligaments are strong bands of tissue that connect one bone to another. The torn ligament is removed during ACL reconstruction and replaced with a strip of tissue that generally links muscle to bone (tendon). The graft tendon is harvested from another portion of your knee or a dead donor.

ACL reconstruction is an outpatient operation performed by a specialist who specializes in bone and joint surgery.