Anterior Cruciate Ligament

Measuring an average of 38 millimeters long and 11 millimeters wide, the anterior cruciate ligament, also known as the ACL, is an important stabilizer of the knee. It is the main structure that prevents the tibia from moving forward over the femur during knee movements. ACL tear is one of the most common knee injuries. The population's increased participation in sports and recreational activities puts more people at risk of ligament rupture.

Anatomy of the Anterior Cruciate Ligament

The anterior cruciate ligament connects the femur to the tibia. It is inserted into the innermost portion of the femur, in a region known as the lateral condyle of the femur, runs along the knee joint, extending for approximately 38 millimeters, and inserts into the tibia.

The ACL is formed by two bundles,anteromedial and posterolateral, which are tensioned according to the degree of knee flexion. The anteromedial bundle is tensioned when the knee is flexed and the posterolateral bundle, when the knee is near to full extension.

How the Injury Occurs

The most common injury mechanism is a twist associated with a knee lever, in which the patient's foot is stuck on the ground and the body rotates over the joint.

What a Person Feels When the ACL Tears

After the torsional mechanism, the patient's knee usually hurts a lot and an important effusion can be noticed. In some situations, the patient may hear a pop at the time of the twist. Often, it is difficult to the doctor to assess the knee right after an injury due to the intensity of the pain, however, after a good analgesia and talking to the patient, it is possible to perform a careful physical examination to look for injuries.

Some time later, a person with an ACL tear may feel the knee a little loose or lack confidence in the knee, depending on the movement performed.

It is worth remembering that an ACL injury can be total or partial and that even partial injuries can cause instability in the knee.

It is important to see an orthopedic doctor after suffering a knee sprain.

Necessary Exams

Some imaging exams can help the doctor when there is a suspicion of an anterior cruciate ligament tear, such as X-rays and magnetic resonance imaging. In addition to visualizing the ligament itself, these exams allow a more detailed evaluation of other structures that may be injured during the sprain, such as the bone, cartilage, menisci, other ligaments, among others.

Visualization of the intact anterior cruciate ligament on knee MRI

Treatment

Once torn, the anterior cruciate ligament usually does not heal enough, meaning that even after healing, the knee remains unstable. This residual instability can damage other structures in the joint. Some factors are taken into consideration when choosing the best treatment for injuries, such as age, occupation and level of sporting activity.

Non-Surgical Treatment

In some specific situations, non-operative treatment may be considered. When there is a partial ligament tear that does not cause instability, physical therapy may be appropriate for the patient's rehabilitation. In addition, when the patient has a complete injury of the ligament but does not play sports that involve changes of direction and does not complain of recurrent instability, non-operative treatment may also be considered.

Surgical Treatment

Since a torn anterior cruciate ligament causes great instability in the knee, the patient usually feels insecure when moving the joint after the injury. In addition, repeated knee twists usually happen, which can cause injury to other structures of the joint, such as the menisci, cartilage and other ligaments.
For this reason, in most cases, surgery to reconstruct the anterior cruciate ligament is indicated. This surgery is performed via video, through arthroscopy.
The objective of the surgery is to replace the torn ligament with a ligament graft. In this way, the graft heals and joint stability can be reached.

Graft Options (Ligament Substitutes)

Ligament grafts are tissues used to replace the injured structure. In the case of anterior cruciate ligament reconstruction, the most frequently chosen substitutes are the hamstrings (gracilis and semitendinosus), the patellar tendon, the quadriceps tendon and grafts from tissue banks (cadaver). In Brazil, the most commonly used grafts are the hamstrings, which are my first choice of grafts in anterior cruciate ligament reconstruction surgeries.

How the Anterior Cruciate Ligament Reconstruction Surgery is Performed?

Anterior cruciate ligament reconstruction surgery follows certain steps depending on the surgical technique used.

ANESTHESIA - Surgery begins with patient's anesthesia. Most often, it is performed a spinal anesthesia, which is administered to the lumbar region. This anesthesia provides excellent analgesia during the surgical procedure and for a few hours after the surgery. It is important to note that the patient remains sedated throughout the procedure. Another option is general anesthesia, usually associated with another anesthesia near the knee, called peripheral nerve block. The choice of anesthesia is made after a discussion between the surgeon and the anesthesiologist and must have the patient's consent.

LIGAMENT RECONSTRUCTION - After anesthesia and preparation of the patient, the surgery begins. A small incision is made in the inner part of the knee. Through this, the tendons of the gracilis and semitendinosus muscles are harvested and prepared to be used as ligament replacements. Then, small incisions are made in the joint line of the knee. A video camera is placed through one of them and the instruments used for joint manipulation are inserted through the other. The next step of the surgery is to check for joint injuries and remove the remaining part of the torn ligament. Then, two bone tunnels are drilled: one in the femur and the other in the tibia. The before prepared graft is then passed through the tibial bone tunnel, through the joint and through the femur bone tunnel. After the graft is correctly tensioned, it is fixed to the bone. There are also some fixation devices available, but, in general, the femur is fixed with an absorbable screw or a small plate (button); and the tibia is fixed with an absorbable screw. After the graft is fixed, a new joint inspection is performed to check the positioning and range of motion of the knee. In addition, we usually perform some maneuvers to check the stability of the joint. After all the checks, the surgical incisions are closed with stitches and a dressing is applied. After the surgical procedure is completed, the patient is taken to the anesthesia recovery room and then to the bedroom.

AFTER SURGERY AND HOSPITAL DISCHARGE - Rehabilitation begins in the first few hours following the surgical procedure, when the patient is encouraged to move the operated knee and get out of bed to walk. A pair of crutches may be used in the first two weeks after surgery, if the patient does not feel confident walking without them. This initial training for walking with crutches is carried out in the hospital, with the help of a team of physiotherapists. Generally, patients who have undergone anterior cruciate ligament reconstruction surgery are discharged from hospital the day after the procedure. In some situations where the surgery is completed early in the morning, the patient can go home the same day.

Rehabilitation with Physiotherapy

Post-operative rehabilitation with physiotherapy is essential for a successful outcome. Initially, rehabilitation consists of modalities to improve pain and inflammation in the knee, as well as manipulation to restore range of motion. Progressively, treatment evolves according to the protocols used and the patient gradually restores muscle strength, stretching and balance.