POSTERIOR CRUCIATE LIGAMENT - DNB Orthopaedics MS Orthopedics MRCS Exam GUIDE - Orthodnb.com

DNB Orthopaedics  MS Orthopedics  MRCS Exam GUIDE - Orthodnb.com

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Tuesday, 17 April 2018

POSTERIOR CRUCIATE LIGAMENT

POSTERIOR CRUCIATE LIGAMENT
  • attached to wide area in medial wall of intercondylar notch of femur – descends posteriorly and laterally – insert in a groove in posterior surface of tibia well below the joint line
  • femoral attachment – half moon shaped and planar – tibial attachment – rectangular – covers the convex surface of posterior tibial plateau
  • surrounded by vascular loose areolar tissue with synovial membrane sustaining the majority of its blood supply from middle geniculate artery
  • length : 38mm – width – 13mm
  • larger anterior portion – smaller oblique posterior portion
  • 70% knee – a structure from post horn of lat meniscus to femur – reinforced the PCL – if passes anteriorly to PCL - anterior meniscofemoral ligt (ligt of Humphrey) – if passes posterior to PCL - posterior meniscofemoral (ligt of Wrisberg)
  • divided into 4 fiber regions – anterior, central, posterior longitudinal, posterior oblique
Biomechanics
  • prevents posterior displacement of tibia in relation to femur
  • anterolateral portion (stronger) acts predominantly in flexion and posteromedial in extension
  • is vertically than orientally oriented – so is in the axis of knee rotation – guide the screw home mechanism – IR of femur at terminal extension
Mechanism of Injury
  • knee flexed – posterior force on tibia- mid substance injury
  • fall on flexed knee with foot in plantar flexion
  • hyperflexion/ hyper extension
Clinical features
  • intact PCL – flexion knee 900 – anterior proximal tibia positioned 1cm anterior to distal femoral condyle – normal anterior step off
  • posterior subluxation when knee flexed to 900- posterior sag sign of Godfrey
  • Posterior drawer test
    • 70-900 knee flexion – graded in comparison with opposite knee
    • loss of anterior step off with proximal tibial eminence remaining anterior to distal femur – 1+ posterior drawer
    • proximal tibial eminence translated posteriorly to point in which it is flush with distal femoral condyle – complete disruption of PCL – 2+ posterior drawer
    • translation beyond the posterior of distal femoral condyles – PCL disruption + posterolateral ligament injury - 3+ posterior drawer
  • quadriceps active drawer
    • supine – knee flexed 70-90- drawer performed
    • quadriceps contraction evokes anterior translation of tibia
Imaging
  • X ray – lateral view shows avulsion of PCL from tibia
  • Stress radiograph – increased posterior translation of > 8mm – complete rupture
  • MRI – can reveal the site of injury, associated injuries
  • Bone scan – evaluating the progress in a case of isolated PCL insufficiency
Non surgical Treatment
  • bracing – quadriceps strengthening


Reconstruction of PCL
  • indicated in injuries of PCL associated with other other injuries like ligt injuries, knee dislocation etc
  • delayed 1-2 wks after injury – to painful intra articular reaction to subside – patient to regain full motion and strength
  • reconstruction done using medial gastrocnemius, semitendinosus, gracilis, Achilles tendon grafts, b-pt-b autografts – arthroscopic or open
  • two band two femoral canal reconstruction – PCL reconstruction using b-pt-b autografts – grafts passed through single tibial tunnel, two femoral tunnels – anterolateral graft being tensioned in 900flexion – posteromedial graft tensioned in 300 flexion
Isometric point
  • about 11mm from junction of the notch and trochlear groove on roof of intercondylar notch – extends 1cm from roof in posterior direction
  • femoral site is more crucial to isometry
Complications of PCL reconstruction

  • loss of motion
    • MC – flexion loss more – d/t improper graft placement or inadequate rehab
    • femoral tunnel position – more important – if anterior to isometric point – increased graft tension w/ flexion loss
    • loss of extension or flexion contracture – d/t prolonged immobilization
  • failure to obtain objective stability
    • poor graft selection – IT band, medial head of gastrocnemius, hamstring insufficient strength
    • improper tunnel placement – femoral tunnel posterior to the isometric point – graft lax – can not prevent posterior sag and drawer
  • failure of reconstruction
    • ignoring associated ligt injuries
  • neurological injuries
    • tourniquet palsy – neuropraxia
    • direct injury of tibial N with guide wire etc
  • vascular complications
    • injury to popliteal artery
  • osteonecrosis
    • local trauma to medial femoral condyle – drilling and soft tissue dissection
    • curettage and autogenous bone grafting

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