ACL Injury

Anatomy of ACL (Knee) ACL stands for anterior cruciate ligament and is one of the two ligaments in the center of the knee. A ligament is a fibrous structure made of collagen which connects bones together. In the knee, the ACL starts at the end of the femur bone and runs diagonally to the top of the tibia. The ligament prevents hyperextension of the knee and stops the tibia from sliding too far forward underneath the femur. It also facilitates knee rotation.

ACL Injuries:
ACL injuries usually occur during activities that involve hyperextension or pivoting of the knee. In sports such as soccer, football, basketball and skiing, the foot is often planted with the knee bent causing the tibia to pivot on the femur, or a sudden direction change can stress the ligament. These are contact sports in which the knee is often struck from the outside and the resultant force can drive the tibia forward while the femur stays in place or is driven backward. Injuries are graded based on the amount of ligament tearing including:

• Grade I, where the ligament is stretched but not torn,
• Grade II, which is a more severe, partial tear in some fibers
• Grade III, which is a severe trauma with a complete tear.

Females are more likely to suffer an ACL injury and studies show that women soccer players are three to five times more at risk than their male counterparts. Reasons are thought to include the smaller notch size that the ACL attaches to in women and hormonal differences such as estrogen levels, which may weaken the ligaments. Women also have less muscle mass than men and tend to take a more erect body position when landing from jumps or changing activities. These factors increase stress on the ACL.

Symtoms:
Common signs and symptoms of ACL injury include:

• A "pop" is sometimes felt or heard in the knee during a strain or twist injury.
• Swelling can occur immediately following the injury, indicating internal bleeding in the knee joint.
• Knee pain is experienced by most patients but is not a symptom by itself.
• A buckling or "giving way" of the knee is felt by many patients.

Diagnosis:
The physician will first obtain the patient's injury history, including symptoms. This is followed by a physical exam which includes manual tests on the movement of the tibia in relation to the femur to determine the integrity of the ACL. Other ligaments and structures may also be examined for injury. Patients may first need ice, elevation and rest to reduce pain and swelling before manual tests can be conducted. An arthrometer, a machine which measures joint looseness, may be used as an interim option.

X-Rays and MRIs, which assesses soft tissue damage, may also be used. If the diagnosis remains in doubt, a surgical procedure called a diagnostic arthroscopy may be necessary to examine the tissue with a fiber optic lens inserted through a small incision and attached to a video camera. The necessity of this procedure is rare.

Treatments:
Partial tears can usually be treated with rehabilitation and bracing. In addition, complete tears in older patients or patients with lower physical demands are usually treated non-operatively. However, for physically active people, complete tears will often require a complete reconstruction of the ACL to prevent further damage and stabilize the knee.

• Immediate Treatment includes the application of ice, wrapping of the knee to decrease pain and swelling and elevation to decrease swelling and reduce pain. After the acute injury and a formal diagnosis, the orthopaedist will decide on the best treatment options based on the patient's age, activity level, recurrence of knee instability and age of injury.
• Non-Operative Treatment: Rehabilitation therapy involves Range of Motion and Strength Exercises, which are used to restore full knee function. These include bending and strengthening the knee while sitting or riding a stationary bike. By strengthening the muscles surrounding the knee, particularly the hamstrings, the ACL job of stabilizing the knee can be assumed by these muscles. The body's movement in space is monitored by nerves, located in ligaments, and tendons and muscles, which send signals to the brain to coordinate activity and protect against injury. These damaged nerves must be retrained in Proprioception exercises so the muscles will move the joint properly again. Knee braces are sometimes used to serve different functions of treatment. Although today's models are lighter weight, a proper fit is still required by a trained brace specialist. There are two types of functional ACL braces, hinge-post strap and hinge post-shell. These incorporate some form of rigid frame and are designed to attempt to control forward translation of the tibia from under the femur. Heavy bracing for isolated ACL injury is rarely used at Emory's Sports Medicine Center because of the many preferable, innovative treatment options available to us.
• Surgical Treatment: About one third of all patients will not require surgery. However, young, physically active patients who can't or don't wish to slow down, patients with instability while performing non-strenuous activities, and the majority of patients with injuries to multiple knee ligaments have better outcomes with surgery. A successful outcome also takes a considerable patient commitment to rehab following surgery. For optimal results, surgery shouldn't be performed until the patient demonstrates a 0-90 degree range of motion, has functional quadriceps musculature and a cool knee, with reduced swelling.
  
  There are three fundamental types of surgery for ACL injuries including;
  • Direct repair, in which the torn ligaments are sutured to promote healing (which is unreliable).
  • Extra-Articular Procedures involve securing a portion of a tendon outside the knee across the knee joint to increase knee stability. However the tendon is unable to perform the same function as the ACL and the stability is usually inadequate.
  • ACL Reconstruction: This is the gold standard and the preferred surgery for ACL injury. The other methods discussed are much less effective and rarely used anymore. Reconstruction involves placing the torn ACL with another form of soft body tissue called a graft.
    The graft is obtained from somewhere else on the patient's body (autograft) or can be donated by another person at death (allograft). The autograft is preferred because it heals more reliably, and since it is the patient's own tissue, has no risk of disease transmission. The risk is low with an allograft and it is often used when patients have too little tissue to harvest, have multiple ligaments to repair or, due to age, should experience minimal surgical trauma.
    After removal of the damaged ACL, tunnels are drilled in the tibia and femur in the same orientation as the removed ACL, and the graft is positioned in the same location. The new ACL graft will span the inside of the knee joint and inside tunnels on both sides of the joint, and then be fixed into position with the use of screws or other sturdy device. These devices may vary, but are similarly reliable and are typically determined by the surgeon. The screws or fixation devices are only temporary because after several months, the soft tissue graft should heal to the surrounding bone.

The commonly used grafts to replace the ACL include:

• The Patellar Tendon connects the quadriceps muscle to the tibia via the patella (knee cap). It is a good graft choice because it is large and strong. The bone ends attached to the patella and tibia allow for bone-to-bone healing, which is the best kind.
• The Hamstring graft uses multiple strands of hamstring tendons to create a very strong composite graft. The harvesting process of the graft is less painful, with a smaller incision, but the healing is not as efficient as with the Patellar. The rehabilitation process can take as long as six to eight weeks until the tendon heals to the bone.
• The Quadriceps Tendon, which connects the muscle to the patella, has soft tissue at one end and bone at the other. It is not a favored technique.

ACL Reconstruction is typically done arthroscopically, (a minimally invasive procedure using pencil-like instruments with fiber optics attached which project the internal joint images on a video camera). The physician will either use a single or double incision technique, which has similar results. And, the procedure is typically performed on an outpatient basis, using general or spinal anesthesia.

Recovery/Rehabilitation:
The rehabilitation process will vary depending on the type of graft. In some cases, the patient is encouraged to immediately do exercises or even ride an exercise bike to mobilize the knee. The following is a typical rehabilitation schedule:

Phase I: (immediately after surgery through week two)
Emphasizes control of inflammation and full range of motion, full extension and 90 degrees of knee flexion. Achieve Quadriceps control, educate patient about process, and Patellar mobilization to prevent loss of knee motion. Patient will remain on crutches for seven to 10 days or until comfortable.

Phase II: (two weeks to six weeks).
Strengthening with light weights and sports cords, full range of motion, continued graft protection and improvement of endurance and proprioception, (use of treadmill/step master, etc.).

Phase III: (six weeks through three-four months).
Improve patient's knee confidence progression in strength power and proprioception. Jogging followed by straight running at 3 months.

Phase IV: May return to sports, depending on graft and activity
Full pain-free range of motion, sufficient strength and proprioception. Advanced lifting and activities, customized to patient's normal activity level.

Phase V: Return to sport, usually at 6 months.
Patient must meet all recovery criteria with no soft tissue or range of motion complaints. The goal is a safe return to sports. Functional bracing may be recommended for the first one to two years for the patient's psychological confidence.

The patient is usually seen by the physician at 2 weeks, 6 weeks, 3 months, 6 months and one year following surgery. There are minimal complications with ACL reconstruction, with infection rates at 0.2% and bleeding complications at 1%. Loss of motion is the most commonly sited complication. Another risk is anterior knee pain. These potential complications are why the rehabilitation process is so critical, including range of motion, quadriceps and patellar mobility during the first two weeks following surgery.

The success of ACL reconstruction is truly dependent on a team effort made up of the surgeon, therapist and the patient.