ACL INJURY

ANTERIOR CRUCIATE LIGAMENT INJURY

The anterior cruciate ligament (ACL) originates from the tibial plateau just medial and anterior to the tibial eminence.

The ACL tracts from the tibia superiorly, laterally, and posteriorly, to its insertion on the posterior aspect of the medial wall of the lateral femoral condoyle.

The ACL is composed of 2 bundles, the anteromedial bundle and the posterolateral bundle.  

The ACL provides 85% of the total restraining force to anterior translation of the tibia. An ACL tear is a common injury that occurs in all types of sports. This injury usually occurs during a sudden cut or deceleration, as it typically is a noncontact injury.

The patient states, "I planted, twisted, and then heard a pop."

Before the advent of arthroscopic knee surgery in the early 1970s, ACL tear was often a career-ending injury.

PATHOPHYSIOLOGY

Like all ligaments, the anterior cruciate ligament (ACL) is composed of type I collagen.

The ultrastructure of a ligament is close to that of tendons, but the fibers in a ligament are more variable and have higher elastin content. Ligaments receive their blood supply from their insertion sites.

The vascularity within a ligament is uniform, and each ligament contains mechanoreceptors and free nerve endings that are hypothesized to aid in stabilizing the joint.

Avulsion of ligaments generally occurs between the unmineralized and mineralized fibrocartilage layers. The more common ACL tear, however, is a midsubstance tear. This type of tear occurs primarily as the ligament is transected by the pivoting lateral femoral condyle.

FREQUENCY

Epidemiologic studies estimate that approximately 1 in 3000 individuals sustains an ACL injury each year in the United States.

MORTALITY/MORBIDITY

Not a single report of mortality was found.

Morbidity was divided into 5 classes.

The first class included patients who were symptomatic with activities of daily living (ADL).

The second class included patients who were able to perform all ADL.

Patients in the third class were able to perform mildly stressful sports (eg, jogging, swimming, biking, and cross-country skiing).

The fourth class included patients who were able to perform moderately stressful sports, including baseball, alpine skiing, racquet sports, dance, and lacrosse.

The fifth class included patients who returned to perfect health and were capable of performing very stressful sports, such as soccer, basketball, football/rugby, volleyball, gymnastics, and hockey.

Post-surgery status of patients was as follows:

• Remained class 1 - 3.3%

• Remained class 2 - 1.4%

• Attained class 3 - 11.8%

• Attained class 4 - 17%

• Returned to class 5 - 66.5%

SEX

According to numerous studies, female athletes sustain a greater number of anterior cruciate ligament (ACL) injuries than do male athletes. Data demonstrated that women have a 2.4 and a 4.1 times greater chance of incurring ACL injury when compared with males in soccer and basketball, respectively.

AGE

Anterior cruciate ligament injuries occur most commonly in individuals aged 14-29 years. These years correspond to a high degree of athletic activity.

CLINICAL

HISTORY

Obtain as much information as possible directly from the patient. The important facts can be clarified by asking questions about the following:

• Mechanism of injury

• Pain

• Feeling/hearing a pop

• Feeling knee give out

• Ability to continue playing sport

• Swelling

• Loss of knee motion

• History of previous knee injury

PHYSICAL

Up to 50% of patients with acute knee injuries who report feeling or hearing a snapping or popping sound are found to have an anterior cruciate ligament (ACL) injury.

A hemarthrosis almost always is present because of the vascular supply to the ACL. When a complete ligamentous tear occurs, pain may begin immediately, followed by resolution.

Immediately following injury, minimal effusion or spasm is present, so ACL injury usually can be identified easily. Several hours after injury, effusion and spasm make diagnosis of an ACL tear more difficult.

To determine the patient's normal amount of laxity, examine the uninjured knee first.

• Perform the Lachman test.

  • This test is performed with the knee in 30° of flexion, with the patient lying supine.

  • Using one hand on the anterior aspect of the distal femur and a second hand behind the proximal tibia, attempt to displace the tibia forward from the femur.

  • A positive Lachman occurs when no endpoint is encountered. The degree of excursion may also indicate an ACL tear.

• Another test to detect ACL tears is the anterior drawer.

  • Perform this test with the knee at 90° of flexion, with the patient lying supine.

  • Place both hands behind the proximal tibia and attempt to displace the tibia forward from the femur.

  • If there is more than 6 mm of tibial displacement, an ACL tear is suggested.

  • The anterior drawer test is not very sensitive and has been found to be positive in only 77% of patients with complete ACL rupture.

CAUSES

Anterior cruciate ligament (ACL) injuries have no single cause. ACL injuries can be related to extrinsic factors and intrinsic factors.

Numerous studies document the fact that poor levels of conditioning correlate directly with increased levels of injury. Research also has demonstrated that improved conditioning results in reduced numbers of injuries.

• Body and movement factors

  • The first 2 factors, body movement and positioning, play a big role in ACL injuries.

  • Noyes and colleagues demonstrated that most ACL injuries (ie, 78%) occur without contact. Most of these injuries occur upon landing after a jump. The Noyes study involved only female basketball players, but the capacity of the knee to plant and turn or to absorb the shock of a jump is relevant to men and women in all sports.

• Muscle strength

  • Muscle strength is the last of the extrinsic factors that affect the ACL. The hamstring is an ACL agonist working in concert with the ACL to prevent anterior tibial translation. Conversely, the quadriceps acts as an antagonist to the ACL, generating force that promotes anterior tibial translation. Ideally, a balance exists between these opposing forces to protect the knee; however, the quadriceps averages 50-100% greater muscle strength than does the hamstring.

  • Strength coaches often emphasize quadriceps strengthening and ignore hamstring strengthening, further exacerbating the inequality.

• Several intrinsic factors can contribute to ACL injuries.

  • Joint laxity is one such factor. Significant controversy surrounds this topic, because published studies are contradictory about whether or not increased laxity contributes to ACL injuries.

  • The Q angle is the acute angle between the line connecting the anterior superior iliac spine, the midpoint of the patella, and the line connecting the tibial tubercle with the same reference point on the patella. Theoretically, larger Q angles signal increases in the lateral pull of the quadriceps muscle on the patella and put medial stress on the knee. Because lower extremity alignment cannot be altered, no recommendation can help to minimize the athlete's risk of ACL rupture; however, the dynamic position of the tibia can be improved with internal rotation exercises for the tibia (eg, medial hamstrings).

  • A narrow intercondylar notch may be a predictive factor for ACL rupture. According to various reports, athletes who sustain ACL injuries often have narrow notch widths compared with fellow athletes with uninjured knees.

DIAGNOSIS

LABORATORY STUDIES

• Lab studies are not indicated in the evaluation and diagnosis of anterior cruciate ligament injuries.

IMAGING STUDIES

• Magnetic resonance imaging (MRI)

  • MRI of the knee usually is recommended prior to surgery for evaluation of the other ligaments and the menisci, because findings can influence the treatment plan.

  • MRI helps the surgeon to have the correct equipment at hand prior to beginning the surgery.

  • The sensitivity of MRI has been shown to be greater than 95% and the specificity to be approximately 98%, with a positive predictive value of 95% and a negative value of nearly 99% with fast spin-echo techniques.

PROCEDURES

• Perform aspiration of any large hemarthrosis, if indicated, under aseptic conditions, to alleviate patient discomfort. The presence of fat globules suggests an intra-articular fracture.

• Radiographs may demonstrate an avulsed fragment just lateral to the tibial plateau. This type of fracture, referred to as a Segond fracture, represents an avulsion of the middle third of the lateral capsule from the tibial plateau; it is also known as a lateral capsule sign.

TREATMENT

PHYSICAL THERAPY

The key to successful treatment of an anterior cruciate ligament (ACL) tear is proper and early rehabilitation.

Preoperative and postoperative rehabilitation programs are similar initially. Swelling control and restoration of motion and strength are the goals of each.

The postoperative rehabilitation program begins as soon as the patient awakens from anesthesia, especially because patients are discharged earlier now than they were in previous years.

Quadriceps co-contractions make up the first exercise that patients should be taught for the maintenance of terminal extension.

Passive motion is emphasized with active flexion and assisted extension in the sitting or prone position to ensure good leg control (ie, ability to flex the hip and lift the leg against gravity without assistance.)

A continuous passive motion machine (CPM) can be used to establish 0-30° of motion immediately postoperatively and to progress to 60° of knee flexion by the morning following the operation.

The patient then begins gait training with crutches (weight bearing as tolerated), with the knee in an immobilizer.

The patient usually can be discharged on the first postoperative day and should be encouraged to avoid crowds, keep the leg elevated when not ambulating, use the crutches at all times for protection, and continue frequent icing.

REHABILITATION FOR PATELLAR TENDON GRAFTS

The following rehabilitation program is an accelerated program for patellar tendon grafts. Note that the other grafts rehabilitate slightly differently.

This rehabilitation program is classified as a goal-oriented approach. The dates listed are not meant to be followed strictly and can be varied by a day or 2, depending on the physician or the patient's schedule.

On day 3 following surgery, have the patient return to the surgeon for evaluation. Begin therapy on an outpatient basis, concentrating on gait training and other ambulation-oriented activities. The goal is to maintain terminal knee extension and progression toward 90° of flexion. The therapist emphasizes a normal heel-to-toe gait pattern, and the patient may weight bear as tolerated on the involved leg. Continue passive flexion ROM exercises.

Have the patient increase quadriceps activity, introducing the partial squat with progression from bilateral to unilateral, placing increased body weight on the extremity involved at no more than 45° of flexion.

Continue these exercises for 1 week. Continue the knee immobilizer when ambulating and continue regular icing of the knee.

On day 10 following surgery, have the patient return to the surgeon for evaluation.

Advance therapy to include wall slide-squats and a stationary bike as tolerated.

Place emphasis on terminal extension, progressive flexion, and full weight-bearing ambulation with normal heel-to-toe mechanics.

In a controlled environment (no pets, children, or distractions), have the patient begin practicing crutch ambulation while out of the knee immobilizer. The patient should achieve full terminal knee extension and approximately 90-100° of knee flexion.

Three to 4 weeks after the surgery, the aggressive patient is ambulating with normal gait mechanics. At this point, the knee immobilizer can be removed.

Advance the patient's activity to include loaded squats, swimming, eccentric quadriceps strengthening, bridging with a physioball, and a stair stepper. During this time, if the therapist is not observant, the patient can develop tendonitis of the quadriceps tendon or other repetitive use injuries of the lower extremity.

Application of ice after each therapy session is very important.

Six weeks after surgery, release the patient to light jogging or bicycling. If the patient is older and has concomitant degenerative joint disease, encourage bicycling.

The graft is still very weak at this stage, so advise the patient that it is important not to fall. The patient should jog only on a track or other flat protected surface. At this point, active ROM should be approaching 0-125° with minimal or no joint effusion.

Work on balance and Proprioception with activity drills.

At 3 months, recommend that the patient begin a gradual return to normal activities. At this point, most people do not require bracing, but occasionally, some athletes request a brace to increase their own comfort level when competing.

OPEN KINETIC CHAIN (OKC) & CLOSED KINETIC CHAIN (CKC) EXERCISES

Significant discussion surrounds the difference between OKC and CKC exercises during ACL rehabilitation.

The difference concerns the assumption that CKC exercises are safer than OKC exercises because they place less strain on the ACL graft, producing less patellofemoral pain.

The second assumption is that CKC exercises are more functional and are equally effective in improving quadriceps muscle force production.

With regard to safety, OKC and CKC exercises can be applied in a manner that minimizes the risk of excessive graft strain and patellofemoral compression.

Using different knee joint motion excursions for each type of exercise is the key to risk reduction. When OKC knee extensions are performed, limit knee joint motion to more flexed positions.

During CKC lower extremity exercises, limit knee joint motions to more extended positions.

MEDICAL ISSUES/COMPLICATIONS

• The primary goals in the treatment of anterior cruciate ligament (ACL) rupture are restoration of function in the short term and the prevention of long-term pathologic changes in the knee. Nonoperative treatment is a reasonable approach in patients who are not athletically active.

• Research has demonstrated that the natural history of untreated complete injuries of the ACL consists of the progression of symptomatic instability to recurrent injuries. These injuries damage the menisci and the articular cartilage, eventually leading to osteoarthritis and osteoarthrosis.

• Complications from ACL surgery generally arise during surgery. Complications include the following:

  • Extravasation of irrigation fluid during arthroscopy

  • Posterior femoral cortex compromise during endoscopic reaming of the femoral tunnel

  • Paresthesias along the lateral aspect of the knee

  • Improper handling of the graft (eg, dropping it on the floor)

  • Bruising and/or hematoma formation

  • Blood loss

  • Improper alignment of the tunnels, causing graft impingement

  • Improper graft placement, making the graft too short and thus not allowing the knee to reach full terminal extension

• The main complication of ACL surgery during the postoperative period is rupture of the graft. Careful and conservative physical therapy (PT) during the first 8-12 weeks is important.

SURGICAL INTERVENTION

Several options exist for the patient who elects to have surgery. For complete rupture, no local healing response is detectable at the injury site, and a graft must be used to replace the ACL.

Today, 4 options are used.

The first 3 types are autografts using the central one third of the patellar ligament (considered a bone-ligament-bone graft), the quadruple semitendinosus/gracilis tendon, or the quadriceps tendon. The fourth type of graft is a cadaveric allograft.

• Autografts

  • The patellar ligament with its bony ends has been a popular ACL replacement because of its high ultimate tensile load (~2300 N), its stiffness (~620 N/mm), and the possibility for rigid fixation with its attached bone graft.

  • By comparison, the dimensions of a round, 10 mm quadruple semitendinosus/gracilis tendon graft (hamstring graft) are more comparable to those of the intact ACL, and its ultimate tensile load has been reported to be as high as 4108 N. The quadruple tendon graft also may provide a multiple bundle replacement graft that better approximates the function of the 2-bundle ACL. Disadvantages of this soft-tissue graft include concern over tendon healing within the osseous tunnels and a lack of rigid bony fixation. A 1998 study from Japan suggests that aggressive early rehabilitation after an ACL reconstruction using the hamstring graft has more risk for residual laxity than does the patellar tendon graft.

  • The quadriceps tendon graft has been shown to have an ultimate tensile load of as high as 2352 N. This graft has become an alternative replacement graft, especially for revision ACL surgeries and for patients with multiple ligament injuries in the knee.

  • Cadaver studies have shown that the strength of fixation between the patellar tendon graft and the hamstring graft is equal to approximately 450 N, but the patellar graft can achieve fixation strength of as high as 1000 N. Grafts fixed to bone close to the articular surface (ie, patellar tendon grafts) undergo less strain and are stiffer than are those grafts fixed outside of drill holes (ie, hamstring grafts).

• Allograft

  • Allograft tissues are harvested from human donors and typically include either the patellar tendon or the Achilles tendon.

  • Allografts are used for multiple ligament reconstructions and revisions of ligament reconstructions, as well as for the treatment of patients who are not high-performance athletes. However, the reduction of tensile strength that occurs with sterilization is a concern, as is the risk of inflammatory reactions.

Ultimately, the decision as to which graft is best is still a matter of contention.

The agreement is that the patellar and hamstring grafts are superior to the quadriceps graft and the allograft; however, the decision as to which is the better of the patellar and hamstring grafts depends on which surgeon is operating.

With regard to osteoarthritis, the type of graft does not appear to influence the development of osteoarthritis.

In spite of the type of graft, a certain percentage of patients develop osteoarthritis in the reconstructed knee, especially patients with concomitant or subsequent meniscectomy.

OTHER TREATMENT

Some patients, especially those who are minimally involved in sports, elect not to have surgery and instead choose bracing.

Several custom and off-the-shelf, anterior cruciate ligament–specific braces are available. For patients who are involved in vigorous sports, the use of braces without surgical stabilization is not recommended.

MEDICATION

The goal of pharmacotherapy is to reduce morbidity.

NONSTEROIDAL ANTI-INFLAMMATORY DRUGS

These agents have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclooxygenase activity and prostaglandin synthesis.

Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions.

IBUPROFEN (Motrin, Ibuprin)

DOC for patients with mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Adult: 600-800 mg PO tid

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Caution in congestive heart failure, hypertension, and decreased renal and hepatic function; caution in anticoagulation abnormalities or during anticoagulant therapy

NARCOTICS

Pain control is essential to quality patient care. If nonsteroidal anti-inflammatory drugs (NSAIDs) are not sufficient, then narcotics may be given.

Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial to patients who have sustained trauma or injuries.

ACETAMINOPHEN AND CODEINE (Tylenol #3)

Indicated for the treatment of mild to moderate pain.

Adult: 1-2 tab PO q4-6h prn

COX-2 INHIBITORS

These drugs can be used as an alternative if the patient has GI upset or a history of GI bleeding with NSAID use. Because of the cost, these medications are not always a first-line choice.

CELECOXIB (Celebrex)

Inhibits primarily COX-2. COX-2 is considered an inducible isoenzyme, being induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity.

At therapeutic concentrations, COX-1 isoenzyme is not inhibited; thus, GI toxicity may be decreased. Seek the lowest dose of celecoxib for each patient.

Adult: 200 mg/d PO qd; alternatively, 100 mg PO bid.