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Orthopaedics HARIBO > ACL > Flashcards

ACL Flashcards

1
Q

Reasons for failure of ACL graft

A
  1. Surgical error (tunnel malpositioning, inadequate tensioning or fixation of the initial graft)
  2. Failure to recognise a secondary laxity (eg postero lateral corner)
  3. Biological failure, ie failure of graft incorporation or ‘ligamentisation’
  4. Rehab issues
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2
Q

Complications of ACL recon

A

Continuing instability may be due to :

  1. Immediate graft failure, ie poor fixation
  2. Suboptimal tunnel placement - either the graft being too vertical (with correction of AP laxity but not rotational stability) or the tunnels being too anterior (femoral and tibial tunnels) or posterior (tibial tunnel)
  3. Cyclical creep of the graft due to inappropriately advanced accerelated rehab
  4. Traumatic graft rupture due to too early a return to contact sport

Other complications include :

  1. Loss of motion
  2. Infection (superficial, deep)
  3. Long term anterior knee pain
  4. Saphenous nerve irritation or neuroma formation
  5. Cyclops lesion formation - scar tissue anterior to the graft usually associated with anterior tibial tunnel placement
  6. Hardware complications
  7. Neuro vascular complications
  8. Fracture of the tibia, femur or patella
  9. Development of a complex regional pain syndrome
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3
Q

Determinants of outcome in ACL reconstruction

A
  1. Graft strength
  2. Graft fixation
  3. Other factors than stability, which are important for long-term outcome (pain, ROM, OA changes)
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4
Q

Load to failure of native ACL

A

2000 N

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5
Q

Classic acute history of ACL tear

absent in up to 30% of ACL injuries

A
  1. Non-contact rotational injury
  2. Swelling normally present with one hour (due to haemarthrosis)
  3. ‘pop’ or ‘snap’
  4. Usually cannot continue in the sport im which the patient was participating
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6
Q

Examination in ACL injury

A
    • Lachman test (ap laxity at 20° of knee flexion with a poor end point) - most specific
    • Anterior drawer sign (knee flexion at 90°)
    • pivot glide or pivot shift
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7
Q

Segond fracture

A

Avulsion injury of the lateral tibial plateau that is very suggestive of ACL injury with lateral ligament complex injury

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8
Q

Aims of rehab before ACL recon

A
  1. Regain full extension and flexion of the knee
  2. Rehabilitate the quadriceps and hamstring mechanisms
  3. Normal gait pattern
  4. Eliminate swelling
  5. Restore symmetry to the lower limbs
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9
Q

Features of acute ACL injury in MRI

normal MRI scan does not exclude an ACL injury

A
  1. Disruption of the ligament
  2. Laxity of the ligament
  3. Secondary changes to PCL alignment
  4. Bone bruising
  5. Sometimes interstitial damage to the ligament causing a ‘sausage effect’
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10
Q

Why should the knee be ‘quiet’ at the time of ACL reconstruction?

A

To minimise the risk of arthrofibrosis

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11
Q

Structure that is most effective in providing stability of knee rotation

A

Postero-lateral bundle of the ACL

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12
Q

Goals of ACL recon

A
  1. Stabilise the knee joint
  2. Restore normal kinematics
  3. Prevent early onset degenerative arthrosis
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13
Q

Anatomy ACL

A
  1. Intra-articular but extra-synovial structure
  2. Blood supply from the middle genicular artery, arising from the popliteal artery
  3. Provides proprioceptive feedback that is protective to the knee, provides stability (anterior translation and rotational stability)
  4. AM bundle is tighter in flexion, PM bundle is tighter in extension
  5. Mean length of 31-38mm and width of 11mm
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14
Q

Risk factors for ACL tear

A
  1. Hyperlaxity
  2. Genetic predisposition
  3. Raised BMI
  4. Hormones
  5. Female gender (relative risk ratio 2-6 times than males)
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15
Q

Goals of prevention programs (ACL injuries)

A
  1. Decrease peak vertical ground reaction force
  2. Increase knee flexion angle
  3. Decrease knee valgus
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16
Q

Consequences of tunnel malpositioning

A
  1. Impingement
  2. Deficits in ROM
  3. Recurrent instability
  4. Graft failure
17
Q

Autografts (ACL)

A
  1. Hamstrings (semitendinosus and gracilis, doubled to create a 4-strand ACL graft)
  2. Bone-patella tendon bone
  3. Quadriceps with or without bone block
18
Q

Weak link in any ACL recon

A

Graft fixation on the tibia

–> graft axis is parallel to the applied force whilst its bone mineral density is considerably less than the distal femur

19
Q

Which ACL recon technique entirely spares the the femoral physis (where growth occurs)?

A

All-inside technique

20
Q

Most common surgical error in arthroscopic ACL recon

A

Anterior femoral tunnel placement, often due to poor visualisation

May cause loss of knee flexion
May cause graft overstretching and failure

21
Q

Empty lateral wall

A

= empty notch

Sign on coronal MRI

indicates avulsion of ACL from the femoral origin

22
Q

Bone bruises

A

Trabecular microfractures

Occur in more than half of acute ACL injuries

23
Q

What should be achieved prior to surgery?

A

Full ROM and good quadriceps strength

24
Q

Why primary repair of ACL tears currently not recommended?

A

Myofibroblasts ‘coat’ the ends of the ACL stumps, making primary healing unlikely

25
Q

Vertical graft placement results in

A

Decreased rotational stability

26
Q

Anterior placement of femoral tunnel results in

A

Flexion loss

27
Q

PCL injury most commonly as a result of

A

Direct blow to the anterior tibia with the knee flexed

28
Q

Interference screw divergence results in

A

Reduced graft pullout strength

29
Q

Too anterior tibial tunnel results in

A

Roof impingement with extension tight in flexion

30
Q

Too posterior tibial tunnel results in

A

Impingement with the PCL

Orthopaedics HARIBO (12 decks)

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