Sports Medicine — ACL Tears

Sports Medicine

ACL Tears

By Dr. Jack Dreisen

“As I am not privy to the type of injury Oregon players sustain or the severity of it, I can only discuss shoulder injuries in general.”  — Dr. Dreisen

Anterior Cruciate Ligament (ACL) Tears

If you’re a sports fan and/or participant, you’ve probably heard of ACL injuries — but do you know what they are and how they are treated?

In a nutshell, an ACL injury is a tear in the Anterior Cruciate Ligament (ACL), which is a ligament inside the knee that connects your upper leg and lower leg. It helps keep the knee stable. ACL injuries can range from minor injuries to complete tears, which can cause severe pain and immobility.

ACL injuries are among the most common sports-related knee injury, according to the Mayo Clinic. About 150,000 new cases occur in the United States each year.

In fact, high school athletes are more likely to suffer ACL injuries than any other age group.

They are especially susceptible because during puberty bones grow in length but not in strength. This leads to decreased control of the knee, which increases the risk of injury.

Athletes involved in sports such as football, basketball and soccer — which involve abrupt stopping, cutting, and jumping — are especially prone to these injuries.

ACL injuries are caused when the knee is hyperextended beyond its normal fully straightened range.

They typically occur when athletes suddenly turn and twist their knee with their feet remaining on the ground.

About 70 percent of the injuries do not involve contact with other athletes, according to the American Orthopaedic Society for Sports Medicine.

Click to see a video replay of Dennis Dixon’s injury.

Anatomy of the Knee

We will now explore ACL tears. We begin with the anatomy of the knee, the ACL, and the meniscus.

The bone structure of the knee joint is formed by the femur, the tibia, and the patella. The ACL is one of the four main ligaments within the knee that connect the femur to the tibia.

The knee is essentially a hinged joint that is held together by the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL) and posterior cruciate (PCL) ligaments. The ACL runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee.

The weight-bearing surface of the knee is covered by a layer of articular cartilage. On either side of the joint, between the cartilage surfaces of the femur and tibia, are the medial meniscus and lateral meniscus. The menisci act as shock absorbers and work with the cartilage to reduce the stresses between the tibia and the femur.

Figure 5. Knee Anatomy (normal and with ACL tear)

The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. The incidence of ACL injuries is currently estimated at approximately 200,000 annually, with 100,000 ACL reconstructions performed each year. In general, the incidence of ACL injury is higher in people who participate in high-risk sports, such as basketball, football, skiing, and soccer.

Approximately 50 percent of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage.

Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella).

Two wedge-shaped pieces of cartilage act as “shock absorbers” between your thighbone and shinbone. These are called meniscus. They are tough and rubbery to help cushion the joint and keep it stable.

Menisci tear in different ways. Tears are noted by how they look, as well as where the tear occurs in the meniscus. Common tears include longitudinal, parrot-beak, flap, bucket handle, and mixed/complex.

Sports-related meniscal tears often occur along with other knee injuries, such as anterior cruciate ligament tears.

The natural history of an ACL injury without surgical intervention varies from patient to patient and depends on the patient’s activity level, degree of injury and instability symptoms.

The prognosis for a partially torn ACL is often favorable, with the recovery and rehabilitation period usually at least three months. However, some patients with partial ACL tears may still have instability symptoms. Close clinical follow-up and a complete course of physical therapy helps identify those patients with unstable knees due to partial ACL tears.

Complete ACL ruptures have a much less favorable outcome. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.

About half of ACL injuries occur in combination with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to ACL injury. With chronic instability, up to 90 percent of patients will have meniscus damage when reassessed 10 or more years after the initial injury. Similarly, the prevalence of articular cartilage lesions increases up to 70 percent in patients who have a 10-year-old ACL deficiency.

Treatment

Nonsurgical Treatment

In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability. This may be supplemented with the use of a hinged knee brace. However, many people who choose not to have surgery may experience secondary injury to the knee due to repetitive instability episodes.

Surgical treatment (click to see a video about surgical reconstruction of ACL) is usually advised in dealing with combined injuries (ACL tears in combination with other injuries in the knee). However, deciding against surgery is reasonable for select patients. Nonsurgical management of isolated ACL tears is likely to be successful or may be indicated in patients:

• With partial tears and no instability symptoms
• With complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
• Who do light manual work or live sedentary lifestyles
• Whose growth plates are still open (children)

During the surgery, doctors will typically drill a hole through the tibia into the femur and thread a tissue from a chosen tendon through the holes.

ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time. Therefore, the torn ACL is generally replaced by a substitute graft made of tendon. The grafts commonly used to replace the ACL include:

• Patellar tendon autograft (autograft comes from the patient)
• Hamstring tendon autograft
• Quadriceps tendon autograft
• Allograft (taken from a cadaver) patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibialis tendon

Patients treated with surgical reconstruction of the ACL have long-term success rates of 82 percent to 95 percent. Recurrent instability and graft failure are seen in approximately 8 percent of patients.

The goal of the ACL reconstruction surgery is to prevent instability and restore the function of the torn ligament, creating a stable knee. This allows the patient to return to sports. There are certain factors that the patient must consider when deciding for or against ACL surgery.

Patient Considerations

Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment. This includes older patients who have previously been excluded from consideration for ACL surgery. Activity, not age, should determine if surgical intervention should be considered.

In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The surgeon can delay ACL surgery until the child is closer to skeletal maturity or the surgeon may modify the ACL surgery technique to decrease the risk of growth plate injury.

A patient with a torn ACL and significant functional instability has a high risk of repeat injuries.

After surgery, patients have to wear a knee brace and go through rehabilitation and physical therapy. The whole process generally takes six to nine months. During that time, patients have to devote 30 to 60 minutes a day to doing strengthening exercises.

Exercises include quad sets (where one tightens the quad muscle and holds it for a few seconds), straight leg raises (when the patient tightens his/her quad and lifts the leg up while keeping it straight), leg presses, and squats.

Athletes who wish to return to their previous level of competitiveness usually undergo surgery, which is the only way to effectively treat a broken ACL.

Surgery has the best long-term outcomes, but return to sport after surgery is about six months of rehabilitation.

It is common to see ACL injuries combined with damage to the menisci (50 percent), articular cartilage (30 percent), collateral ligaments (30 percent), joint capsule, or a combination of the above. The “unhappy triad,” frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.

In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes.  As many as 50 percent of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.

Surgical Choices

During the surgery, doctors will typically drill a hole through the tibia into the femur and thread a tissue from a chosen tendon through the holes.

“Surgery actually wasn’t that scary,” said Nguyen. “Afterward, I stayed overnight in one of the recovery rooms, and that was it.”

After surgery, patients have to wear a knee brace and go through rehabilitation and physical therapy. The whole process generally takes six to nine months. During that time, patients have to devote 30 to 60 minutes a day to doing strengthening exercises.

Exercises include quad sets (where you tighten the quad muscle and hold it for a few seconds), straight leg raises (when you tighten your quad and lift your leg up while keeping it straight), leg presses, and squats.

Athletes who wish to return to their previous level of competitiveness usually undergo surgery, which is the only way to effectively treat a broken ACL.

“Surgery has the best long-term outcomes, but return to sport after surgery is about six months [of rehab],” said Zimmerman, the Carle Sports Medicine doctor.

Patellar tendon autograft – The middle third of the patellar tendon of the patient, along with a bone plug from the shin and the kneecap is used in the patellar tendon autograft. Occasionally referred to by some surgeons as the “gold standard” for ACL reconstruction, it is often recommended for high-demand athletes and patients whose jobs do not require a significant amount of kneeling.

In studies comparing outcomes of patellar tendon and hamstring autograft ACL reconstruction, the rate of graft failure was lower in the patellar tendon group (1.9 percent versus 4.9 percent). In addition, most studies show equal or better outcomes in terms of postoperative tests for knee laxity (Lachman’s, anterior drawer and instrumented tests) when this graft is compared to others. However, patellar tendon autografts have a greater incidence of postoperative patellofemoral pain (pain behind the kneecap) complaints and other problems.

The pitfalls of the patellar tendon autograft are:

• Postoperative pain behind the kneecap
• Pain with kneeling
• Slightly increased risk of postoperative stiffness
• Low risk of patella fracture

Hamstring tendon autograft – The semitendinosus hamstring tendon on the inner side of the knee is used in creating the hamstring tendon autograft for ACL reconstruction. Some surgeons use an additional tendon, the gracilis, which is attached below the knee in the same area. This creates a two- or four-strand tendon graft. Hamstring (gracilis muscle) graft proponents claim there are fewer problems associated with harvesting of the graft compared to the patellar tendon autograft including:

• Fewer problems with anterior knee pain or kneecap pain after surgery
• Less postoperative stiffness problems
• Smaller incision
• Faster recovery

The graft function may be limited by the strength and type of fixation in the bone tunnels, as the graft does not have bone plugs. There have been conflicting results in research studies as to whether hamstring grafts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during objective testing. Recently, some studies have demonstrated decreased hamstring strength in patients after surgery.

There are some indications that patients who have intrinsic ligamentous laxity and knee hyperextension of 10 degrees or more may have increased risk of postoperative hamstring graft laxity on clinical exam. Therefore, some clinicians recommend the use of patellar tendon autografts in these hypermobile patients.

Additionally, since the medial hamstrings often provide dynamic support against valgus (an abnormal outward turning of a bone, especially of the hip, knee, or foot) occasionally used to indicate an inward turning  stress and instability), some surgeons feel that chronic or residual medial collateral ligament laxity (grade 2 or more) at the time of ACL reconstruction may be a contra-indication for use of the patient’s own semitendinosus and gracilis tendons (the gracilis tendons are paired bands of connective tissue made of collagen that connect the gracilis muscles to bone. The gracilis tendons enable the contracting gracilis muscles to adduct the hip and flex and medially rotate the flexed knee) as an ACL graft.

Quadriceps tendon autograft – The quadriceps tendon autograft is often used for patients who have already failed ACL reconstruction. The middle third of the patient’s quadriceps tendon and a bone plug from the upper end of the knee cap are used. This yields a larger graft for taller and heavier patients. Because there is a bone plug on one side only, the fixation is not as solid as for the patellar tendon graft. There is a high association with postoperative anterior knee pain and a low risk of patella fracture. Patients may find the incision is not cosmetically appealing.

Allografts – Allografts are grafts taken from cadavers and are becoming increasingly popular. These grafts are also used for patients who have failed ACL reconstruction before and in surgery to repair or reconstruct more than one knee ligament. Advantages of using allograft tissue include elimination of pain caused by obtaining the graft from the patient, decreased surgery time and smaller incisions. The patellar tendon allograft allows for strong bony fixation in the tibial and femoral bone tunnels with screws.

However, allografts are associated with a risk of infection, including viral transmission (HIV and Hepatitis C), despite careful screening and processing. Several deaths linked to bacterial infection from allograft tissue (due to improper procurement and sterilization techniques) have led to improvements in allograft tissue testing and processing techniques. There have also been conflicting results in research studies as to whether allografts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during testing.

Recently published literature may point to a higher failure rate with the use of allografts for ACL reconstruction. Failure rates ranging from 23% to 34.4% have been reported in young, active patients returning to high-demand sporting activities after ACL reconstruction with allografts. This is compared to autograft failure rates ranging from 5% to 10%.

The reason for this higher failure rate is unclear. It could be due to graft material properties (sterilization processes used, graft donor age, storage of the graft). It could possibly be due to an ill-advised earlier return to sport by the athlete because of a faster perceived physiologic recovery, when the graft is not biologically ready to be loaded and stressed during sporting activities. Further research in this area is indicated and is ongoing.

Surgical Complications

Infection. The incidence of infection after arthroscopic ACL reconstruction has a reported range of 0.2 percent to 0.48 percent. There have also been several reported deaths linked to bacterial infection from allograft tissue due to improper procurement and sterilization techniques.

Viral transmission. Allografts specifically are associated with risk of viral transmission, including HIV and Hepatitis C, despite careful screening and processing. The chance of obtaining a bone allograft from an HIV-infected donor is calculated to be less than 1 in a million.

Bleeding, numbness. Rare risks include bleeding from acute injury to the popliteal artery (overall incidence is 0.01 percent) and weakness or paralysis of the leg or foot. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which may be temporary or permanent.

Blood clot. A blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing stroke. This risk of deep vein thrombosis is reported to be approximately 0.12 percent.

Instability. Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique (reported to be as low as 2.5 percent and as high as 34 percent) is possible. In other words, repeated injury after the initial injury and surgery can result in poorer and poorer outcomes.

Stiffness. Knee stiffness or loss of motion has been reported at between 5 percent and 25 percent.

Extensor mechanism failure. Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.

Growth plate injury. In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The ACL surgery can be delayed until the child is closer to reaching skeletal maturity. Alternatively, the surgeon may be able to modify the technique of ACL reconstruction to decrease the risk of growth plate injury.

Kneecap pain. Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies between 4 percent and 56 percent in studies, whereas the incidence of kneeling pain may be as high as 42 percent after patellar tendon autograft ACL reconstruction.

Rehabilitation

Physical therapy is a crucial part of successful ACL surgery, with exercises beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.

Postoperative Course – In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.

The knee is iced regularly to reduce swelling and pain. The surgeon may dictate the use of a postoperative brace and the use of a machine to move the knee through its range of motion. Weight-bearing status (use of crutches to keep some or all of the patient’s weight off of the surgical leg) is also determined by physician preference, as well as other injuries addressed at the time of surgery.

Rehabilitation – The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.

The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.

The patient’s sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes four to six months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.

As one can see, ACL tears are serious business. However, better surgical techniques. technology, rehabilitation practices, and preventive measures are making such injuries more treatable with more successful returns to sports activities and daily living.

If all else fails, then having a recovering athlete earnestly study this 2012 cheerleaders picture might help cheer him up and give him hope:

Next time, we will explore MCL and LCL injuries.

GO DUCKS!!!!!