Surgical Treatment of Posterior Cruciate Ligament Tears

Reviewed by Dr Josh Petterwood MBBS | Accredited Orthopaedic Registrar

PCL Anatomy

  • Extra-articular
  • 32-38mm
  • 11mm2 at midpoint
  • Two bundles
    • Large AL
    • Smaller PM
  • Femoral insertion
    • Broad, vertical footprint, anterolateral medial femoral condyle
    • Semicircular or oval
    • 209 mm2
    • AL – 118 mm2
    • PM – 90 mm2
    • Associated with medial intercondylar ridge proximally
  • Tibial Insertion
    • Central facet posterior surface of tibia
    • 1/1.5cm from joint line
    • Center of insertion 7mm from posterior cortex
    • Posterior horn of MM directly anterior
  • Meniscofemoral ligaments of Humphry and Wrisberg
    • 17% of cross-sectional area of PCL complex
  • Posterolateral Corner
    • Biceps
    • ITB
    • Polpliteus
    • Popliteofibular lig
    • Capsule
    • Arcuate lig
    • Fabellofibular lig

PCL Biomechanics

  • Primary restraint to posterior tibial translation
  • Ultimate load
    • AL – 1120 N
    • PM – 419 N
  • Non-isometric
    • In flexion – AL lengthens/more vertical, PM shortens/more horizontal
    • Conflicting data/ideas about this

Mechanism of Injury

  • Posteriorly directed force to tibia
    • Hyperflexion
    • Fall on flexed knee
    • Dashboard MVA
    • Ruckmen/martial arts
    • In major knee trauma resulting in multiple ligamentous injury

Examination Findings

  • Posterior Drawer at 90 deg
GradeAmount of Translation (cm)
11-5
26-10
3>10
Grading of Posterior Drawer Test
  • Lachman
  • Posterior Drawer in IR/ER
  • Quadriceps active test
  • Dynamic posterior shift
  • Dial test at 30/90 deg
  • External rotation recurvatum
  • Reverse pivot shift
  • Complete the exam to assess associated injuries

Imaging

  • Plain films
    • Acutely for avulsion
    • Chronic associated degenerative change
  • MRI

Management

PCL Reconstruction

  • Results not as good/predictable as ACL
  • Controversy exists regarding
    • Tibial fixation
    • Number of graft bundles
    • Femoral tunnel placement
    • Graft tension
  • Lack of evidence to support one technique over another

Transtibial Reconstruction

  • Most common method
  • Graft passed proximally/posteriorly
  • ‘Killer curve’
  • Sawing may lead to graft elongation and failure
  • Aperture fixation may reduce this
  • Technically difficult/dangerous

Tibial Inlay Technique

  • Arthroscopic femoral tunnel placement
  • Open bone trough created for tibial fixation
  • Anatomical
  • No ‘killer curve’
  • Short graft decreases posterior laxity
  • Markholf et al
    • 2000 cycles
    • 0.5 Hz
    • 32% vs 0% failure
    • Graft thickness maintained
    • Less elongation

Graft Bundle Options

  • Single bundle
    • AL bundle reconstructed
  • Double bundle
    • Both AL and PM bundles
  • In theory anatomic restoration leads to decrease in posterior tibial translation and in situ forces more closely resembling normal
  • Double bundle technique may over constrain
  • Conflicting studies (mostly cadaveric)

Femoral Tunnel Positioning

  • Particularly in single bundle reconstruction
    • AL/central/PM
    • Anterior/posterior
  • Markholf
    • Posterior – tends to over constrain and lead to increase graft forces
    • Anterior – increased laxity at 0-45 deg, normal graft forces
    • Central – increased graft forces at 0-45 deg
  • Anterior probably recommended

Angle of graft entry

  • ‘Critical corner’
  • Outside-in vs Inside-out
  • Greater angle in inside-out technique may be a theoretical disadvantage
  • Not well investigated biomechanically

Double bundle

  • Double drilling may weaken distal femur, interrupt blood supply and lead to increase risk of fracture
    • Wiley et al
      • Significantly lower load to failure
      • Protected WB

Graft Tensioning

  • Single bundle
    • Normally tensioned 70 – 90 deg flexion
    • Problem with residual laxity in extension
    • Carson et al
      • 90 AL/0 PM restored similar forces to native PCL

Combined Instability

  • In setting of combined PCL and PLC injury
    • Double bundle reconstruction more likely to reduce posterior tibial translation
    • Also more likely to improve rotational stability
    • Neither adequately repair rotational instability
  • Combined PCL/PLC reconstruction recommended

Take home message

  • Most (Gr I/II) isolated PCL injuries
    • do well with active rehabilitation program
  • Isolated Gr III and combined PCL/PLC injuries require reconstruction
  • Much controversy surrounds
    • Tibial fixation
    • Graft selection and tensioning
    • Femoral tunnel positioning
  • Many recent gains in anatomical and biomechanical understanding
  • Not enough clinical evidence

References

  • J Am Acad Orthop Surg 2009;17: 435-446