Anterior Cruciate Ligament Rupture | ACL

Western Health Orthopaedic Registrar presentation – ACL Rupture by Dr Liam Halliday

Western Health Orthopaedic Registrar presentation – ACL Management: Operative vs Non-operative by Dr Amy Gibbens

Anatomy

• multiple fascicular subunits within larger functional bands
• 38mm long & 10mm wide
• smaller than the PCL
• Origin:
  • posteromedial aspect LFC
• Insertion:
  • intercondylar eminence
• Blood supply:
  • middle geniculate artery

Physiology of the ACL

Strength

• normal tensile strength of 2500 newtons in young adults
• Loss of the ACL produces abnormal kinematics & also frequently results in major degenerative changes
• Anteromedial bundle of the ACL is the most nearly isometric component throughout the ROM of the knee
• Posterolateral bundle has the highest load when the knee is fully extended

Function of the ACL

• Two important roles
  • Proprioceptive
    • ACL contains numerous proprioceptive nerve endings
  • Mechanical
    • carries loads throughout the entire range of flexion & extension of the knee
    • resisting anterior tibial translation
    • to a lesser degree tibial translation & abduction during knee flexion
    • primary restraint to anterior tibial translation
    • ACL carries only small loads during normal daily function; normal daily loads are only at about 20% of failure capacity
    • highest loads on the ACL occur through
      • Quadriceps powered extension of the knee
      • Hyperextension of the knee
      • Excessive internal tibial rotation
      • Excessive valgus or varus forces if a collateral ligament is torn
    • ACL is a viscoelastic structure that can adjust to stresses over time

Compensatory mechanisms

• Other anatomical structures in the knee can compensate for the loss of the ACL
• Posterolateral complex: controls anterior tibial translation & anterolateral tibial rotation
• Medial collateral ligament & posteromedial complex control anterior translation of the medial side of the joint
• Hamstrings: restrain anterior tibial translation
• Posterior horn of the medial meniscus

Biology of reconstruction

• 6 weeks
  • graft is synovialized while the centre necroses.
  • Revascularization leads to cellular proliferation that repopulates the graft.
  • Complete revascularization takes around 20 weeks, & is accompanied by an ↑ in the size of the graft (up to 3 times ↑)
• At one year after reconstruction the graft has 30-50% of the strength of the native ACL
• collagen fibrils are smaller in diameter
• Reconstruction of the ACL with patella tendon or hamstrings graft is effective in reducing anterior tibial translation
• However, it is less effective in restraining the anterior tibial translation when a knee has a valgus & internal tibial rotation force

Aetiology

• Rapid deceleration or rotational injury to knee
• Audible pop in 30-50% of patients
• Direct contact – 30%
  • typically involve at least one cruciate & one collateral ligament
• Indirect contact – 70%

Epidemiology

• 1 in 3000 per annum in USA. 50 000 reconstructions per annum in USA
• More frequently in females: (basketballers soccer)
  • Narrower notch
  • Oestrogen

Associated Injuries

• Association with other injuries of the knee
• An isolated injury of the ACL is thought to be physiologically impossible
• However the injuries to other structures may not be major
• Associated injuries to major ligament complexes ↑ the likelihood that non-operative management of the ACL will result in functional instability
• commonest associated injury is to the MCL
• Injury to a meniscus is frequently associated with ACL rupture (50%). In acute injuries it is the lateral meniscus that is most frequently injured, but in chronic injuries it is the medial meniscus. If a meniscus is lost the knee will be more likely to go on to Osteoarthritis. Approx 50% of meniscal lesions associated with ACL rupture can be repaired

Pathology

Meniscal injuries

• are frequently found – more than 50%.
• acute ACL injuries
  • lateral meniscus is injured more frequently
• chronic injuries
  • medial meniscus is more frequently involved

History

• Classic pop heard in 30-50%
• patient’s level of activity is the single most important factor in the decision about whether or not to operate

Level	Activities
1	jumping, cutting, pivoting sports – basketball, soccer
2	heavy manual labour, side to side sports – skiing, tennis
3	light manual work, noncutting sports – jogging, running
4	sedentary activity without sports

Examination

• Haemarthrosis
  • within hours of injury
  • Around 70% of patients with acute traumatic knee haemarthroses will have an ACL injury
• Joint line tenderness
  • may suggest meniscal or capsular injury but is not specific in the first 10 – 14 days of injury

Lachman test

• most sensitive test
• performed with the knee in slight flexion
  • it is at this point where the secondary restraints are most lax
• patient lying supine on the table with the involved extremity on the side of the examiner.
• With the patient’s knee held between full extension & 15° flexion, the femur is stabilized with one hand while firm pressure is applied to the posterior aspect of the proximal tibia in an attempt to translate it anteriorly
• positive test
  • indicating disruption of the ACL
  • proprioceptive &/or visual anterior translation of the tibia in relation to the femur with a characteristic mushy or soft end point

Anterior drawer test

• tests the anteromedial bundle of the ACL (tight in flexion)
• If the patient has intact medial collateral ligaments the anterior drawer test may be negative because they act as secondary restraints to anterior translation with the knee flexed to 90°.
• “the drawer sign is minimal in isolated ruptures of the ACL”.
• sign is “maximal” it is almost certain that the medial ligament has been involved
• False negatives
  • in the acute setting
    • Haemarthrosis & synovitis may make it impossible to flex the knee to 90°
    • Strong hamstrings may be impossible to overcome
    • strong convexity of the medial femoral condyle makes a ball to the socket formed by the concavity of the medial tibial plateau & medial meniscus
• For the anterior drawer test to be positive
  • either the medial structures had also to be torn,
  • or there needed to be peripheral separation of the posterior horn of the medial meniscus

Pivot shift test (McIntosh)

• goes from the reduced position in flexion to the subluxed position in extension.

Jerk test

• goes the other way, from subluxed in extension to reduced in flexion

Significant varus or valgus instability in extension

• indicative of a more severe injury involving multiple ligaments & potentially both cruciates

Investigations

Xray

• Rosenberg (45° flexion PA weight bearing view)
  • signs of chronic ACL deficiency
    • peaking of the tibial spines
    • narrowing of the intercondylar notch
• Segond fracture (avulsion fracture of lateral tibial plateau)
  • pathognomonic of ACL injury
• Physeal injuries in open physes

MRI

• Useful for delineating associated intraarticular pathology
  • meniscal tears
  • assessing the other ligaments
• Bone bruising or marrow changes
  • posterolateral aspect of the lateral tibial plateau
  • midcentral aspect of the lateral femoral condyle
  • Represents chondral fracture or delamination
  • occur in 80-90%

Treatment

Acute

• Control pain & swelling
• Early resumption of weight bearing & muscle activation
• Range of motion exercises
• Important to regain full extension
  • Dependent on quadriceps function

Nonoperative

• Aim is to control swelling & pain, with quick restoration of full range of motion
• NSAIDS
• Physiotherapy
  • Muscle strength should have returned to 90% of the other side before the patient is allowed back to normal activities
• Functional bracing
• Avoid high-risk activities for 6 to 12 weeks after an ACL tear
• May still require minimal operative intervention
  • meniscectomy
  • excision of impinging ACL stump
    • 2-3 months post injury because the stump may shrink

Operative

Options

• Repair alone
• Repair with augmentation
• Extra-articular reconstruction
• Reconstruction with autogenous grafts
• Reconstruction with autogenous grafts & prosthetic augmentation
• Reconstruction with use of allografts or a prosthesis

Direct repair

• Direct repair isn’t strong enough unless there is supplementation with some type of autogenous graft
• Long term retrospective & prospective reviews showed a 40-50% failure rate within 5 years of 400 repairs in 8 different studies

Extra-articular repair

• Examples are the Losee, McIntosh & Ellison repairs, all of which use a strip of iliotibial band.
• They are unsatisfactory because they work by tenodesing the posterolateral aspect of the joint & the ligament is subject to gradual failure as it stretches

Reconstruction

• Reconstruction depends on
  • Patient age
  • Skeletal maturity
  • Activity & skill level
  • Associated meniscal & ligamentous injuries
  • Frequency of instability
  • Patient compliance & motivation

Level	Activities
1	jumping, cutting, pivoting sports – basketball, soccer
2	heavy manual labour, side to side sports – skiing, tennis
3	light manual work, noncutting sports – jogging, running
4	sedentary activity without sports

• Indications
  • Significant Meniscal or associated ligamentous pathology
  • Level 1 or 2 activities
    • patient’s level of activity is the single most important factor in the decision about whether or not to operate
  • Age
    • 40 y.o.
      • is often quoted as the cutoff for operative vs. nonoperative treatment
      • but this is related to the level of activity of the patient
      • 50 year old engaged in vigorous activities would be a candidate for operation
    • Paediatric
      • ACL reconstructions in adolescents with a skeletal age of 14 revealed no growth or angular complications
      • Transphyseal tunnels were used
  • Degree of instability
    • People with generally tight ligaments may be less likely to have problems after an ACL rupture, because secondary stabilizers of the knee are more able to cope in these patients
    • Patients with less than ½ of the ligament torn & no positive signs of ↑ anterior translation can probably be managed nonoperatively
  • Cooperation by the patient
    • Patients must be able to comply with a rigorous physiotherapy program
• Issues
  • Older patient age
    • Similar outcomes & satisfaction in patients older than 40
  • Younger child / adolescent
    • concern is growth arrest
    • activity restriction is impractical in this age group
    • repeated buckling can lead to meniscal & articular damage
    • no evidence in some studies of growth or angular complications
    • concern regarding use of transphyseal metallic fixation
• Goals
  • restore knee stability
  • protect meniscal & articular cartilage
  • minimize periopertive morbidity
• Preoperatively Planning
  • Surgery is delayed until inflammatory phase has subsided
    • This ↓ incidence of arthrofibrosis
  • Joint swelling, ROM, quadriceps function, gait
• Options
  • Graft
    • Autogenous
      • Hamstring
      • Bone Patellar Bone
    • Allograft
  • Fixation
    • Suspension
      • Buttons / Cross pins
      • ‘windshield wiper effect’
        • Graft moves in anterior to posterior plane with flexion/extension of knee
        • → graft abrasion or tunnel expansion
      • ‘Bungee Cord Effect’
        • longituidnal elongation and retraction of graft leads to tunnel widening
    • Aperture fixation
      • Round-threaded metallic screws
      • Bioabsorbable screws
        • Higher risk of tunnel widening and failure
  • Graft choices
    • Options
    • Bone-patellar tendon-bone (BTB)
    • Four strand hamstring autograft
    • Quadriceps tendon
    • Allograft
    • BTB grafts
      • Young, high demand athletes
      • Titanium interference screw fixation allow early ROM, FWB, accelerated rehabilitation
      • Complaints
        • Donor site morbidity: Anterior knee pain: 14-31%, kneeling pain
        • No difference after 2 years
        • Perioperative patellar fractures 0.2%
        • Patellar tendon ruptures
      • Durable, reliable, reproducible method
    • Hamstring – four strand gracilis semitendinosus
      • Advantages
        • Smaller incisions
        • Potentially less perioperative pain
        • ↓ anterior knee pain
      • Disadvantages
        • Initial graft fixation
        • Weakness: resolves within 6-12 months, rarely leads to lasting instability
  • Timing
    • Operations on the ACL are more likely to be complicated by fibrosis if the operation is done in the first 4 weeks after rupture
    • Also more likely to be complicated by fibrosis if the operation is done while the knee is acutely inflamed & the range of motion is restricted
    • operation can be done when the effusion is subsided & a nearly normal range of motion has been obtained. It is technically easier to do when the haemarthrosis is subsided
  • Assessing graft placement on post-op X-rays
    • On the lateral the tibial tunnel should emerge in the anterior half of the middle third of the tibia
• Postoperative care
  • Ice & CPM
    • No long lasting benefits for either. May be some benefits in first several days?
  • Rehabilitation
    • Important
    • Closed vs Open Chained exercises
      • Closed chain exercises, where the knee is axially loaded during quadriceps contraction are thought to cause less strain on the ACL than open chain exercises where the limb isn’t bearing weight
    • Optimal protocol remains controversial

Prognosis

Natural History

• Depends on integrity of menisci & frequency of buckling episodes
• Recurrent episodes of giving way lead to meniscal & articular cartilage damage
• ACL vs instability
  • There is little agreement in the literature about the chance a patient has of progressing to functional instability after an ACL rupture.
  • Figures range from 16% in one study to almost 100% in other studies
• ACL vs OA
  • There is also little agreement on whether or not radiographic evidence of Osteoarthritis will develop; figures show rates of mild Osteoarthritis ranging from 13% (2-10 years followup) to 68% (10-16 years followup)
• ACL vs meniscectomy
  • Around 60% of nonreconstructed ACL injured patients will require meniscectomy within 5 years of injury.
  • Prospective studies have reported lower rates of late meniscal tears requiring surgery – e.g. 24% at 10 years

Results post ACL reconstruction

• 85-95% have clinically stable knees
• 80-94% normal or nearly normal knee
• Patients with intact menisci are much more likely to be happy with their results;
  • at 5-15 years
    • 87% of patients with intact menisci rated their knees as normal or nearly normal compared with
    • 63% of patients requiring meniscectomy
• Poor correlation between the objective physician assessed results & the patient’s perception of knee function & stability.
  • Patients with meniscal lesions may have good objective stability but have poor subjective stability.
  • Patients fixed with hamstring grafts have poorer objective findings on KT1000 testing but equal subjective results
• Failures
  • Unsuccessful long term results of ACL reconstruction range from 5-52% depending on the criteria used for definition
    • 10-15% of Primary ACL reconstruction
    • 20% of revisions
  • 60% of failures are related to poor tunnel placement leading to impingement & failure
• Arthrofibrosis
  • commonest complication after surgery is a knee flexion contracture.
  • Loss of extension is a significant cause of debility.
  • Patients walk with a bent knee gait, have patellofemoral pain, have quadriceps weakness & poor functional results
• Stiffness
  • arthrofibrosis
  • Cyclops lesion
  • Patella infera
  • Poor graft placement with impingement. An ACL graft with notch impingement will demonstrate ↑ T2 signal
  • RSD
• Infection
  • occurs in 0.5%
• Reoperation rates of 5-21%
  • for meniscal problems,
  • hardware problems
  • loss of motion
• Knee pain
  • From the patella
  • From a saphenous nerve neuroma
• Revision ACL surgery
  • Improperly placed tunnels may need to be treated with a two stage procedure with bone grafting of the tunnels as stage one, then redrilling when the tunnels have healed

Complications

• Graft failure
• Graft fixation failure
  • Tunnel Widening
    • Causes
      • Graft position
      • Biological response
    • Types
      • Linear
      • Cavitary
      • Mushroom
      • Conical
• Hardware problems
• Loss of motion
• Reoperation Rate 5-21%
  • Meniscal tears, hardware problems, loss of motion
• Patellar fractures / tendon ruptures 0.2-4%
  • Intraoperatively
  • 6-12 weeks postop with rehabilitation
• Infection 0.5%
• Nonanatomical tunnel placement
• Inappropraite graft tension

Tunnel Widening in Revision ACL Reconstruction by Dr Craig Brown