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Anterior Cruciate Ligament Injury

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Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
> Table of Contents > Anterior Cruciate Ligament Injury

Anterior Cruciate Ligament Injury
Adam J. Farber MD
Basics
Description
  • The ACL is critical for knee function in
    athletes who require knee stability in activities such as running,
    cutting, jumping, and kicking.
  • The ACL originates on the posteromedial
    aspect of the lateral femoral condyle and inserts anterior to and
    between the intercondylar eminences of the tibia.
  • The ACL is composed of 2 bundles—an anteromedial bundle and a posterolateral bundle.
  • The ACL functions as the primary
    restraint to limit anterior tibial translation and as a secondary
    restraint to internal rotation of the tibia.
  • In the skeletally immature patient,
    injury to the ACL most often occurs at the bone–ligament interface, as
    an avulsion of the tibial spine.
  • In the adult patient, rupture of the midsubstance of the ligament is more common.
Epidemiology
Incidence
ACL injuries commonly are associated with sports such as
football, hockey, basketball, lacrosse, gymnastics, wrestling, and
volleyball.
Risk Factors
ACL injury rate is 4–6 times higher in females than males in competitive sports (1).
Etiology
  • Etiologic factors include anatomic
    features, such as an elevated Q angle, notch stenosis, a narrower than
    normal ACL, and neuromuscular factors (landing with decreased knee
    flexion and increased knee valgus).
  • ACL injuries often are the result of a
    noncontact injury that occurs while decelerating, changing direction,
    or landing from a jump.
  • Direct contact to the knee with a valgus
    load and external rotation of the tibia, such as a clipping injury, is
    another common mechanism.
Associated Conditions
  • “Bone bruises” (trabecular
    microfractures), which occur in >50% of acute ACL injuries,
    typically are located on the posterior portion of the lateral tibial
    plateau and near the sulcus terminalis on the lateral femoral condyle.
  • Meniscal injuries (>50%) (2):
    • Acutely, lateral meniscal injuries are more common than medial.
    • In patients with chronic ACL deficiency, medial meniscal injuries are more common than lateral.
  • Collateral ligamentous injuries in the knee
  • Articular cartilage injuries
Diagnosis
Signs and Symptoms
History
  • The injury often is associated with immediate pain and an audible “pop.”
  • Swelling of the knee is noted within a few hours (acute hemarthrosis).
  • The patient often states that the knee feels too unstable to continue playing and that weightbearing is difficult.
Physical Exam
  • A careful physical examination can diagnose most ACL injuries.
  • The results of the physical examination of the injured knee must be compared with those of the normal knee.
  • Inspection usually reveals a moderate to severe effusion.
  • Typically, full knee extension is limited secondary to pain, effusion, hamstring spasm, and ACL stump impingement.
  • Flexion often is limited by effusion.
  • Care should be taken to observe that
    anterior translation or drawer testing is not reducing a posteriorly
    sagged tibia (OSD injury) from a subluxated position.
  • The Lachman test is the most sensitive examination for acute ACL injuries.
    • The knee is placed in 30° of flexion, the femur is stabilized, and an anteriorly directed force is applied to the proximal calf.
    • The examiner assesses the magnitude of anterior translation and the firmness (firm versus soft) of the endpoint.
    • Differences between the injured and uninjured knees are clinically significant.
  • The pivot shift test is used to assess the anterior subluxation of the lateral tibial plateau on the femoral condyle.
    • It is difficult to perform this test in
      an awake patient in the acute setting, but it is helpful in evaluating
      an ACL-deficient knee.
    • This test is especially helpful when the patient is anesthetized.
    • Procedure:
      • Patient supine, knee extended
      • With the tibia internally rotated, apply a valgus force to the knee as it is passively flexed.
      • If, at approximately 20–40° of knee
        flexion, the patient experiences a sudden jerk as the iliotibial band
        reduces the anteriorly subluxated tibia, the test is considered
        positive.
  • The anterior drawer test is the least reliable test for acute ACL injuries (3).
    • The hip is flexed at 45°, and the knee is flexed to 90°.
    • An anterior force is directed by the examiner to the proximal calf.
    • The examiner assesses the magnitude of anterior translation and the firmness (firm versus soft) of the endpoint.
    • Differences between the injured and uninjured knee are clinically significant.
  • Instrumented knee laxity measurements can be performed using a device such as the KT-1000.
    • These devices are useful for quantifying knee laxity objectively, but they are not necessary for diagnosis.
    • A difference of >3 mm of anterior tibial translation between the injured and uninjured knee is considered pathologic.
Tests
Imaging
  • Radiography:
    • Evaluation should include AP, lateral, and tunnel views of the knee.
    • Plain radiographic findings suggestive of
      an ACL injury include a tibial spine avulsion fracture, a Segond
      fracture (lateral capsule avulsion fracture of the tibial plateau), or
      a deepened sulcus terminalis.
  • MRI is the imaging modality of choice for
    evaluating the ACL and associated bony contusions and ligamentous or
    meniscal injuries.
    • MRI has an overall accuracy of 95% in diagnosing ACL injuries (3).
    • On sagittal MRI, an ACL tear is visualized as a discontinuity in the ligament.
Differential Diagnosis
  • Osteochondral fracture
  • Tibial plateau fracture
  • Meniscal injury
  • Cartilage injury
  • MCL or LCL injury
  • OSD injury
Treatment
Initial Stabilization
  • The initial treatment of the acutely
    injured ACL is splinting and the use of crutches for comfort and early
    active ROM. The goal is to obtain full ROM.
  • Ice, elevation, and analgesics are prescribed in the initial postinjury period.
General Measures
  • Treatment decisions should be based on
    many factors, including patient age, activity level, type of sporting
    activity (especially jumping, cutting, and pivoting sports), degree of
    instability, and associated knee pathology.
  • Treatment options in the skeletally
    mature patient include nonoperative interventions and intra-articular
    ligamentous reconstruction.
  • Nonoperative treatment is preferred for elderly patients or those with sedentary lifestyles (see “Physical Therapy” section).
  • For the skeletally immature patient with a midsubstance ACL injury:
    • Some clinicians favor nonoperative treatment and rehabilitation measures until skeletal maturity is reached (3).
    • Others favor physeal sparing surgical reconstructive procedures (4).
  • Nondisplaced and minimally displaced
    tibial spine avulsion fractures in skeletally immature individuals are
    treated with closed reduction.
Activity
  • Patients should be counseled concerning high-risk activities, such as cutting, pivoting, and jumping.
  • Regardless of treatment modality, functional knee bracing after ACL injury is controversial.

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Special Therapy
Physical Therapy
  • Preoperative, postoperative, and
    nonoperative rehabilitation emphasizes early ROM (especially full
    extension of the knee) and early weightbearing.
    • For patients treated nonoperatively or surgically, strengthening is achieved by using closed-chain weightbearing exercises.
    • The goal is to return the function of the hamstring and quadriceps muscles to within 90% of that of the contralateral limb.
    • In patients treated surgically, agility and strengthening exercises typically are started 6 weeks after surgery.
Medication
First Line
  • In the acute period:
    • NSAIDs
    • Acetaminophen
    • Mild narcotic analgesics
Surgery
  • Before surgery, the patient should undergo physical therapy to regain full ROM and minimize swelling.
  • Intra-articular ACL reconstruction currently is favored for:
    • Those with active lifestyles but acute ACL deficiency
    • Those with chronic ACL deficiencies that result in functional instability that endangers the menisci
  • Intra-articular ACL reconstruction with grafting can be performed effectively via either open or arthroscopic techniques.
  • Graft selection depends on patient factors and surgeon preference.
    • Autograft: Bone–patellar tendon–bone, 4-strand hamstrings, or quadriceps tendon
    • Allograft: Fascia lata and Achilles, quadriceps, patellar, hamstring, and anterior and posterior tibialis tendons
    • Allograft is associated with lessened donor-site morbidity, but it has the potential for viral transmission (5).
  • Primary repair is favored for a displaced tibial spine avulsion fracture but is not recommended for a midsubstance ACL rupture.
  • In the skeletally immature patient with a
    midsubstance ACL injury, a variety of reconstructive procedures may be
    performed based on the maturity of the patient (6).
    • Tanner stage 1 patients: Physeal-sparing procedures
    • Tanner stage 2 patients: Partial transphyseal techniques
    • Tanner stage 3 and above (those approaching skeletal maturity): Complete transphyseal reconstructions
Follow-up
Prognosis
  • In the ACL-deficient knee, meniscal tears, cartilage damage, and possibly degenerative arthrosis may ensue.
  • Prognosis is excellent for appropriately selected patients who have undergone ACL reconstruction.
Complications
  • Nonoperative-related (i.e., the chronic ACL-deficient knee):
    • Higher incidence of complex meniscal tears than in surgically treated patients
    • Possibly more prone to development of late osteoarthritis (controversial)
  • Surgery-related:
    • Graft failure, graft impingement,
      quadriceps weakness, patellofemoral pain, infection, arthroscopic fluid
      extravasation and compartment syndrome, deep vein thrombosis, reflex
      sympathetic dystrophy (<1%), nerve and vascular injuries (<1%),
      and arthrofibrosis.
    • Harvesting bone–patellar tendon–bone
      autograft is associated with anterior knee pain, kneeling pain, and
      (rarely) patellar fracture and patellar tendon rupture (3).
Patient Monitoring
Patients should be followed carefully at 4–6-week
intervals to ensure that they regain ROM and strength of the quadriceps
and hamstrings.
References
1. Gray
J, Taunton JE, McKenzie DC, et al. A survey of injuries to the anterior
cruciate ligament of the knee in female basketball players. Int J Sports Med 1985;6:314–316.
2. Noyes
FR, Barber-Westin SD. A comparison of results in acute and chronic
anterior cruciate ligament ruptures of arthroscopically assisted
autogenous patellar tendon reconstruction. Am J Sports Med 1997;25:460–471.
3. Larson RL, Tailon M. Anterior cruciate ligament insufficiency: principles of treatment. J Am Acad Orthop Surg 1994;2:26–35.
4. Stanitski CL. Anterior cruciate ligament injury in the skeletally immature patient: diagnosis and treatment. J Am Acad Orthop Surg 1995;3:146–158.
5. Nemzek
JA, Arnoczky SP, Swenson CL. Retroviral transmission by the
transplantation of connective-tissue allografts. An experimental study.
J Bone Joint Surg 1994;76A:1036–1041.
6. Tanner JM, Davies PSW. Clinical longitudinal standards for height and height velocity for North American children. J Pediatr 1985;107:317–329.
Additional Reading
D’Amato
MJ, Bach BR, Jr. Knee. Section J. Anterior cruciate ligament injuries.
Part 1: ACL reconstruction in the adult. In: DeLee JC, Drez D Jr,
Miller MD, eds. DeLee & Drez’s Orthopaedic Sports Medicine: Principles and Practice, 2nd ed. Philadelphia: WB Saunders, 2003:2012–2067.
Linko
E, Harilainen A, Malmivaara A, et al. Surgical versus conservative
interventions for anterior cruciate ligament ruptures in adults. Cochrane Database Syst Rev 2005;CD001356.
Pigozzi
F, DiSalvo V, Parisi A, et al. Isokinetic evaluation of anterior
cruciate ligament reconstruction: quadriceps tendon versus patellar
tendon. J Sports Med Phys Fitness 2004;44:288–293.
Sloane
PA, Brazier H, Murphy AW, et al. Evidence based medicine in clinical
practice: how to advise patients on the influence of age on the outcome
of surgical anterior cruciate ligament reconstruction: a review of the
literature. Br J Sports Med 2002;36:200–203.
Miscellaneous
Codes
ICD9-CM
  • 717.83 Old disruption of the anterior cruciate ligament
  • 844.2 Acute sprain of cruciate ligament of knee
Patient Teaching
Most patients do not return to their previous level of
activity if they were high-performance athletes, but most patients can
return to sports.
FAQ
Q: If I choose not to undergo ACL reconstruction, what activity modifications will I have to make?
A:
Patients permanently should avoid high-impact or cutting motions and
contact sports. Straight-away running and closed-chain exercises are
excellent for conditioning and strengthening.
Q: If I undergo ACL reconstruction, how long will I be out of sports?
A:
In uncomplicated cases and depending on the sport, athletes can expect
to return to full sports participation in approximately 6–9 months
after ACL reconstruction.
Q: What is the role of bracing to prevent ACL injuries?
A:
Although the issue is controversial, use of knee braces during
aggressive athletic activity, such as football, has not been shown to
decrease incidence of knee injuries and may give the player a false
sense of security.

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