ACL

The anatomy, alignment and position of the ACL in the knee allows it to serve several functions. It not only prevent excessive forward movement of the tibia in relation to the femur during gait or walking, but also provides rotational control of the femur on the tibia during more strenuous activity such as pivoting and cutting, as one would do while playing football, soccer or basketball. The ACL provides stability to the knee joint and prevents excessive motion of the femur and tibia in relation to one another, and therefore from the knee giving out in vigorous athletic activities. It works with the 3 other major ligaments

There are two major mechanisms for injuring the ACL, contact and non-contact.

Contact: This mechanism occurs when a person sustains a forceful blow to the leg, as can occur in athletics such as football and soccer.  The athlete’s tibia or lower leg is restrained or forcefully impacted while the athlete’s momentum forcefully causes increased movement of the joint causing stretching or rupturing of the ligament.  There is often immediate, intense pain as well as the audible sensation of a “pop” with rapid swelling within the knee joint.

Non-Contact: The non-contact mechanism is becoming more frequent, and is estimated to account for up to 80% of all ACL injuries, especially in athletics such as soccer, football, volleyball and gymnastics.  With this mechanism, the foot either remains planted or impacts the ground or playing surface with the knee in a slightly flexed position and bent position called "valgus" with some degree of rotation.  This specific position of the knee, leg and foot under the athlete leads to forces that exceed the tensile strength of the ligament, causing stretching or rupture of the ligament.

So what should you do if you suspect an ACL injury? It is critical to seek urgent evaluation by a specialist trained to evaluate musculoskeletal injuries. First a complete history of the injury will be obtained, focusing on the mechanism of the injury and associated symptoms, as well as what treatment you have received. Next, a complete physical examination will be performed of the injured knee as well as the contralateral, non-injured knee for comparison. This will include specialized tests including a Lachman's test, anterior drawer test, and the pivot shift test. These are specialized tests that are positive in the setting of an ACL injury. When these tests are performed, they will show increased motion of the tibia in relation to the femur. 

Typically, a complete set of x-ray will be obtained evaluating for any fractures, of associated bony injuries.  If an ACL injury is suspected, typically magnetic resonance imaging (MRI) will be obtained to confirm the diagnosis and look for other subtle injuries that may have occurred at the time of the injury, such as meniscus and cartilage injuries. The MRI can usually be obtained in 1-3 days and will be reviewed with you to discuss the findings and the treatment options. If there is significant associated other injuries within the knee including other ligaments, meniscus or cartilage injuries, a knee brace may be prescribed or refraining from bearing weight on the injured extremity may be recommended. In certain instances, if surgery is planned but the knee is very swollen and stiff, physical therapy may be prescribed prior to surgery to improve range of motion of the injured knee, which can prevent severe stiffness after surgery. Additionally, swelling in the knee can inhibit the return of normal knee motion and will sometimes be aspirated, or removed from the knee with a syringe and needle, to facilitate the rehabilitation of the knee.

Treatments (Non-operative)

Not every ACL injury requires surgical treatment. Historically, non-operative treatment has been reserved for older, inactive or obese patients who do not intend to participate in athletics. Also, a patient that has preexisting osteoarthritis or rheumatoid arthritis affecting the injured knee can be treated with non-operative treatment. Furthermore, a patient who has a stable knee on physical exam and is not having clinical episodes of instability where the knee gives out or buckles may potentially be treated non-operatively.

Treating an ACL injury non-operatively consists of anti-inflammatory medications, icing, elevation and compression, along with physical therapy and possibly bracing. Immediate goals are decrease in swelling and pain with gradual return to normal range of motion, strength and gait. Eventually, a return to activities may be attempted, though patients with ACL injuries are permanently susceptible to the knee giving out because of lack of the rotational constraint provided by the ligament. Sometimes these episodes can lead a patient who initially opts for non-operative treatment to consider surgical treatment.

Treatment (Surgical)

The surgical treatment of ACL injuries consists of either repair or reconstruction of the ligament. The repair of the patients native ligament is reserved for pediatric patients who sustain an injury that causes a piece of bone to be avulsed from the tibia rather than tearing the ligament. This injury is far less common. In children, adolescents and adults, reconstruction of the ligament with a replacement tissue is performed. In young children with open growth plates, non-anatomic reconstructions can be performed that attempt to replace the ligament without violating the growth plate. More commonly, in adolescents and adults, anatomic reconstructions are performed that attempt to replace the injured ligament with a graft, or replacement tissue in a manner that restores the patient’s normal anatomy, placing the graft in an identical way to their native ligament.

ACL surgery is one of the more common orthopedic injuries, and is therefore, intensely studied experimentally, both with biomechanical studies evaluating the mechanics and physics of the ACL ligament and different reconstruction techniques, as well as clinical studies looking at patient outcomes. The vast body of knowledge regarding this injury and the treatment continues to grow at a rapid pace. However, there exist many remaining questions and controversies in our quest as surgeons to continually improve upon the care we provide our patients with this injury.  Our goal as surgeons who specialize in ACL reconstruction surgery is to get patients back to action better, faster and safer than ever before. I believe this is possible by implementing the most advanced techniques and cutting edge knowledge while utilizing time tested principles.

Controversies:

Graft options: 

1. Autograft:
   • Bone Patellar tendon – bone (BTB)
   • Hamstring tendon
   • Quadriceps
2. Allograft: higher re-rupture rates in young athletes
3. Synthetic

Technique:

1. Single bundle vs double bundle
2. Medial portal vs transtibial femoral tunnel drilling
3. Outside in vs all inside technique
4. Fixation: suspension vs interference

Rehabilitation after ACL reconstruction surgery typically requires 6-9 months to return to high level athletics, but can take as long as 12 months. Rehab protocols vary from surgeon to surgeon, but generally the rehabilitation after surgery progresses through phases. The 1st phase, immediately after surgery until 6-8 weeks postoperatively, is focused on pain and swelling control and regaining range of motion. If there are other injuries that were addressed at the time of surgery, such as meniscus injuries or cartilage injuries, weight bearing may be limited for up to 6 weeks, requiring crutches or a walker. Typically, if only the ACL reconstruction is performed, full weight bearing can progress as tolerated.  The goals of the 1st phase are normal range of motion and gait.

The 2nd phase begins around 6-8 weeks after surgery and continues to 3-4 months after surgery. This phase is focused on improving strength, focusing on the quadriceps and hamstrings, as well as accessory muscles of the hip and leg. Exercises performed during this phase include squats and leg press, which stimulate co contraction of both the quadriceps and hamstrings. This functions in protecting the ACL graft while it continues to revascularize. Progression to running will also begin towards the end of phase 2.

Progression to the 3rd and final phase begins around 3-4 months postoperatively and focuses on regaining strength and agility, preparing one for return to sporting activities. This phase will employ more ballistic type activities such as cutting and jumping.  When a patient’s strength, agility and endurance, as well as their confidence returns, a patient has completed the rehabilitative program and is ready to return to athletic activities.

Outcomes after ACL injuries vary. We generally use the ability of an athlete or patient to return to their level of activity prior to their injury as a surrogate for an excellent outcome. Although generally our best studies show a return to play around 80-85%, there are some deficits. There are also studies that show the rates of developing osteoarthritis in the knee after surgical treatment for an ACL injury approach. Therefore, further studies are needed to improve our knowledge regarding this injury and its treatment, so that we may continue to improve upon our care for patients with this injury.

1. Infection
2. Nerve injury
3. Blood clots
4. Recurrent instability
   1. secondary to graft rerupture or stretching slowly over time – b/c of improper tunnel placement and graft position, loss of fixation, overly aggressive activity early in rehab
5. Hardware complications
6. Patellofemoral symptoms from quad weakness – secondary to insufficient rehabilitation
7. Inability to return to sport – due to any of the above complications