Anterior cruciate ligament injury


Typically after a noncontact deceleration, a cutting movement or hyperextension, often accompanied by a ‘pop’ with associated knee instability.

Patients typically present with acute injury, sometimes with an associated pop, sensation of tearing of tissues, immediate onset of effusion or any combination of the above.

Occurs as a tear or overstretching of the anterior collateral ligament.

Can result in partial tear or a full tear.

The ACL is most often injured during sports or other activities that make sudden stops and changes in direction.

Most commonly injured ligament in the body.

Accounts for more than 50% of knee injuries.

Costs greater than $7 billion annually.

Highest incidence among young athletes.

At least 200,000 ACL reconstructions performed each year in the U.S.

Incidence difficult to establish since some injuries are not diagnosed.

Incidence at West Point 3.2% for men and 3.5% for women followed over 4 years (Mountcastle).

Majority of tears, 67% in men and 90% in women, occur without physical contact.

40% of injuries are attributed to noncontact mechanisms including pivoting, cutting or jumping.

Injury rate in female athletes ranges from 2-6 times the rate in male athletes, dependent upon the sport.

A systematic review and metaanalysis report an incidence of 0.8 in female athletes and 0.5 in male athletes per 1000 exposures, with soccer posing the greatest risk of ACL injury in female athletes and football in male athletes.

Increased risk in females related to sex differences in leg alignment, increased rate of valgus deformity in women, hormonal factors, increased risk in preovulatory stage of menstrual cycle and changes in neurohormonal control.

Often complicated by concomitant injury of the medial collateral ligament and lateral or medial meniscal tears.

Important aspects of history include a noncontact mechanism of injury, the noting of a popping sound and the early onset of knee swelling due to hemarthrosis from the rupture of the vascular ligament.

In comparison with other lesions: collateral ligament tears do not result in swelling, patients with partial posterior ligament tears can continue to function, and with meniscal tears swelling onset is delayed until the next day.

The Lachman test and the pivot shift test aid in the assessment of the injury.

The Lachman test: patient in a supine position and the outside of the thigh is stabilized and slightly externally rotated and elevated off the bed to produce a flexion angle of 20-30 degree, while the tibia is pulled anteriorly with a second hand-a positive result is indicated by a absence of sensation of a solid stop to anterior displacement of the tibia.

Sensitivity and specificity of Lachman test 85% and 94%, respectively (Crawford).

The pivot test assesses whether there is a sudden subluxation of the lateral tibial condyle on the distal femur when the knee is extended.

The pivot-shift test is it dynamic test of rotatory rlaxity of the knee producing subluxation and reduction of the lateral tibial plateau.

Sensitivity and specificity for pivot shift test is 24% and 98%, respectively (Crawford).

The anterior drawer test involves moving the tibia forward with respect to the femur, with the patient’s knee in the 90° of flexion and feet flat, and an excessive anterior translocation indicates a positive test.

Increases the risk of premature knee osteoarthritis.

Osteoarthritis develops in 50% of patients by 10-20 years after tear.

Diagnosis can frequently be made by history and physical examination.

Isolated ACL tear occurs in less than 10% of cases.

Associated meniscus injuries occur in 60-75% of cases, articular injuries in up to 46% of cases, subchondral bone injuries in 80%, complete collateral tears in 5-24% of cases.

Associated with joint intability, unsatisfactory knee function, decreaed activity, poor knee related quality of life in the short term and increased risk of osteoarthritis.

MRI examination is strongly recommended as part of the diagnostic evaluation, as it is associated with a high sensitivity and specificity of 97% and 100%, respectively for detection of ACL injury.

MRI provides information about associated damage to the articular cartilage, collateral ligaments, meniscus and bones, which if present changes the treatment approach.

Optimal management is not known.

ACL surgical reconstruction is usually recommended for restoration of anterior-posterior as well as rotatory knee laxity in young, healthy individuals who engage in pivoting sports at a highly competitive level.

A randomized trial of young active patients comparing early ACL reconstruction with delayed reconstruction showed no significant difference between group in terms of pain, symptoms of instability, functioning sports and recreation, and knee related quality-of-life.

In a matched-pair analysis involving athletes who did or did not undergo ACL reconstruction, those who had reconstruction had less knee laxity than those who did not have reconstruction, but otherwise no statistically significant differences were present in clinical outcome or costs.

The risk of medial meniscal surgery is doubled when ACL reconstruction is delayed for more than five months after injury and six times as high when delayed for more than one year.

Restoring anterior-posterior and rotary knee laxity may prevent articular Cartilage and meniscus damage, or both.

Although no high level of evidence favors surgery, it is recommended as the initial treatment for top level athletes.

The American Academy of Orthopedic Surgeons recommends: 12 weeks of non-operative treatment for acute isolated ACL tear followed by a reevaluation for the need for surgery.

When surgery is required it is recommended that it be performed within five months after injury to avoid recurrent instability and damage to the meniscus and articular Cartilage.

Treatment includes nonsteroidal anti inflammatory drugs, physical therapy and surgery.

Patients should use crutches while the knee heals, ice packs and knee elevation.

Non-operative therapy involves three months of physiotherapy, anti-inflammatory drugs, range of motion training, strengthening of the quadriceps, hamstrings, hip adductors, and core muscles with a progressive return to active life.

Bracing has not been shown to provide adequate stability restoration.

Putting weight on the knee, or doing any type of activity, makes the process more painful.

In a randomized control trial of 121 young adults with ACL injury rehabilitation plus early reconstruction was not better than rehabilitation plus delayed reconstruction and the latter strategy was associaed with reduced frequency of surgery (Frobell RB).

No significant differences occur in subjective or objective measurements related to the timing of ACL surgery.

However, the timing of surgery affects the development and severity of related soft tissue damage with higher rates of damage to the medial meniscal and medial tibiofemoral cartilage in the group receiving later surgical management.

Complication of ACL reconstruction include superficial wound infections, which occur in less than 1% of individuals.

In a study of athletes who underwent ACL reconstruction, re-injury rates within two years or 4.5% in those who return to play in 33% of those who did not.

Rates of re-injury are significantly higher in individuals who return to play before nine months.

Less common complications include joint infection, postoperative hemarthrosis and quadriceps inhibition, which is the inability to contract the quadriceps muscle.

The most common surgical era is the incorrect positioning of the graft leading to a loss of motion.

Excessive scar tissue formation within the joint may lead to painful restriction of joint motion.

Autografts of the hamstrings using the tendons of the semitendinosus and gracious muscles and the patella tendon have similar results in terms of outcomes and incidence of postoperative osteoarthritis.

The quadriceps tendon as a source for grafting is associated with less damage at the site of tendon harvest than grafts of the patella tendon and with similar patient outcomes.

Reconstruction may use either single-bundle or double-bundle reconstruction, with the latter having a lower risk of a revision.

Allografts have higher costs and a greater rate of graft failure and repeat rupture of the ACL, particularly in young athletes.

Meniscal injuries occur in patients with ACL in about 26-45% of cases, most commonly involving the posterior and peripheral regions.

Meniscal repair outcomes at the time of ACL reconstruction exceed 90% at a minimum of five years follow up.

Collateral ligament injuries with ACL occur in 19-38% of patients and management is determined by the laxity of the ligament.

Surgical collateral ligament repair is required for multiple ligament injuries and severe injuries.

Postoperative rehabilitation consists of measures to establish full range of motion, prevent hypo trophy, diminish pain, diminish swelling, and avoid unnecessary stress to reconstructed ligaments and to any meniscal cartilage repairs.

Postoperative rehabilitation begins within the first week after surgery it continues 6-9 months and includes cryotherapy, soft tissue compression with elastic bandages, immediate weight-bearing as tolerated, eccentric quadricep strengthening, isokinetic hamstring exercises, closed kinetic chain and open chain exercises, and neuromuscular and agility training, dynamic joint stability, movement patterns opposite to those shown to injure the ACL.

Only 40-50% of patients undergoing ACL surgery can return to a pre-surgical/pre-injury level of activity or higher.

It is excepted to return to activity should be delayed for a minimum of nine months from surgery to optimize biologic graft and incorporation and clinical outcomes.

Autografts remain the pref2242ed source for ACL repair.

There is a significant reduction in knee injuries with use of prophylactic knee braces, but evidence for preventing ACL injuries is not clear-cut.

Preventive training programs with biomechanic and proprioception program shows significant reduction in risk of ACL injuries.

Studies show and approximately 100 patients undergoing preventive training programs is required to prevent one single ACL injury.

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