Updated: 4/6/2020

PCL Injury

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  • Injuries may be isolated or combined and often go undiagnosed in the acutely injured knee
  • Epidemiology
    • incidence
      • 5-20% of all knee ligamentous injuries
  • Pathophysiology
    • mechanism
      • direct blow to proximal tibia with a flexed knee (dashboard injury)
      • noncontact hyperflexion with a plantar-flexed foot
      • hyperextension injury
    • pathoanatomy
      • PCL is the primary restraint to posterior tibial translation
      • functions to prevent hyperflexion/sliding
      • isolated injuries cause the greatest instability at 90° of flexion
  • Associated conditions
    • combined PCL and posterolateral corner (PLC) injuries
    • multiligamentous knee injuries
    • knee dislocation 
  • Prognosis
    • chronic PCL deficiency
      • PCL deficiency leads to increased contact pressures in the patellofemoral and medial compartments of the knee due to varus alignment 
      • controversial whether late patellar and MFC chondrosis will develop
  • PCL anatomy  
    • origin
      • posterior tibial sulcus below the articular surface  
    • insertion
      • anterolateral medial femoral condyle  
      • broad, crescent-shaped footprint
    • dimensions
      • 38 mm in length x 13 mm in diameter
      • PCL is 30% larger than the ACL
    •  PCL has two bundles    
      • anterolateral bundle
        • tight in flexion
        • strongest and most important for posterior stability at 90° of flexion
        • mnemonic "PAL" - PCL has  an AnteroLateral bundle
      • posteromedial bundle
        • tight in extension
        • reciprocal function to the anterolateral bundle 
    • lies between the meniscofemoral ligaments  
      • ligament of Humphrey (anterior) and ligament of Wrisberg (posterior)
        • originate from the posterior horn of the lateral meniscus and insert into PCL substance
  • Blood supply
    • supplied by branches of the middle geniculate artery and fat pad
  • Biomechanics
    • strength is 2500 to 3000 N (posterior)
    • minimizes posterior tibial displacement (95%)
  • Classification based on posterior subluxation of tibia relative to femoral condyles (with knee in 90° of flexion)
    • Grade I (partial)
      • 1-5 mm posterior tibial translation
      • tibia remains anterior to the femoral condyles
    • Grade II (complete isolated)
      • 6-10 mm posterior tibial translation
      • complete injury in which the anterior tibia is flush with the femoral condyles
    • Grade III (combined PCL and capsuloligamentous)
      • >10 mm posterior tibial translation
      • tibia is posterior to the femoral condyles and often indicates an associated ACL and/or PLC injury
  • History
    • differentiate between high- and low-energy trauma
      • dashboard injury
      • hyperflexion athletic injury with a plantar-flexed foot
    • ascertain a history of dislocation or neurologic injury
  • Symptoms
    • posterior knee pain
    • instability
      • often subtle or asymptomatic in isolated PCL injuries
  • Physical exam
    • varus/valgus stress
      • laxity at indicates MCL/LCL and PCL injury
      • laxity at 30° alone indicates MCL/LCL injury
    • posterior sag sign
      • patient lies supine with hips and knees flexed to 90°, examiner supports ankles and observes for a posterior shift of the tibia as compared to the uninvolved knee 
      • the medial tibial plateau of a normal knee at rest is 10 mm anterior to the medial femoral condyle
        • an absent or posteriorly-directed tibial step-off indicates a positive sign
    • posterior drawer test (at 90° flexion) post
      • with the knee at 90° of flexion, a posteriorly-directed force is applied to the proximal tibia and posterior tibial translation is quantified 
        • isolated PCL injuries translate >10-12 mm in neutral rotation and 6-8 mm in internal rotation
        • combined ligamentous injuries translate >15 mm in neutral rotation and >10 mm in internal rotation
      • most accurate maneuver for diagnosing PCL injury
    • quadriceps active test post
      • attempt to extend a knee flexed at 90° to elicit quadriceps contraction
      • positive if anterior reduction of the tibia occurs relative to the femur
    • dial test  
      • > 10° ER asymmetry at 30° & 90° consistent with PLC and PCL injury
      • > 10° ER asymmetry at 30° only consistent with isolated PLC injury
    • KT-1000 and KT-2000 knee ligament arthrometers
      • used for standardized laxity measurement although less accurate than for ACL
  • Radiographs
    • recommended views
      • AP and supine lateral
        • may see avulsion fractures with acute injuries
        • assess for posterior tibiofemoral subluxation
        • medial and patellofemoral compartment arthrosis may be present with chronic injuries
      • lateral stress view  
        • apply stress to anterior tibia with the knee flexed to 70°
        • asymmetric posterior tibial displacement indicates PCL injury
        • contralateral knee differences >12 mm on stress views suggest a combined PCL and PLC injury
        • becoming the gold standard in diagnosing and quantifying PCL injuries
      • kneeling stress radiographs of knee
  • MRI  
    • confirmatory study for the diagnosis of PCL injury
  • Nonoperative
    • protected weight bearing & rehab
      • indications
        • isolated Grade I (partial) and II (complete isolated) injuries
      • modalities
        • quadriceps rehabilitation with a focus on knee extensor strengthening    
      • outcomes
        • return to sports in 2-4 weeks
    • relative immobilization in extension for 4 weeks
      • indications
        • isolated Grade III injuries
        • surgery may be indicated with bony avulsions or a young athlete
      • modalities
        • extension bracing with limited daily ROM exercises
        • immobilization is followed by quadriceps strengthening
  • Operative
    • PCL repair of bony avulsion fractures or reconstruction
      • indications
        • combined ligamentous injuries 
          • PCL + ACL or PLC injuries
          • PCL + Grade III MCL or LCL injuries
        • isolated Grade II or III injuries with bony avulsion
        • isolated chronic PCL injuries with a functionally unstable knee
      • techniques
        • primary repair of bony avulsion fractures with ORIF
        • reconstruction options include
          • tibial inlay vs. transtibial methods 
          • single-bundle vs. double-bundle
          • autograft vs. allograft
        • allograft is typically utilized with multiple graft choices available
          • options include - Achilles, bone-patellar tendon-bone, hamstring, and anterior tibialis
      • outcomes
        • good results achieved with primary repair of bony avulsions
        • primary repair of midsubstance ruptures are typically not successful
        • results of PCL reconstruction are less successful than with ACL reconstruction and residual posterior laxity often exists
        • successful reconstruction depends on addressing concomitant ligament injuries
        • no outcome studies clearly support one reconstruction technique over the other
    • high tibial osteotomy
      • indications
        • chronic PCL deficiency
      • techniques
        • consider medial opening wedge osteotomy to treat both varus malalignment and PCL deficiency  
        • when performing a high tibial osteotomy in a PCL deficient knee, increasing the tibial slope helps reduce the posterior sag of the tibia   
          • shifts the tibia anterior relative to the femur preventing posterior tibial translation
Surgical Techniques
  • Arthroscopic transtibial technique 
    • approach
      • standard arthroscopic portals with an accessory posteromedial portal
        • posteromedial portal is placed 1 cm proximal to the joint line posterior to the MCL
        • avoid injury to branches of the saphenous nerve during placement
      • posteromedial corner of the knee is best visualized with a 70° arthroscope either through the notch (modified Gillquist view) or using a posteromedial portal
    • technique
      • transtibial drilling anterior to posterior
      • fix graft in 90° flexion with an anterior drawer 
        • results in knee biomechanics similar to native knee
    • pros & cons
      • risk to popliteal vessels
  • Open (tibial inlay)
    • approach
      • uses a posteromedial incision between medial head of gastrocnemius and semimembranosus 
    • technique
      • used for ORIF of bony avulsion
    • pros & cons
      • biomechanical advantage with a decrease in the "killer turn" with less graft attenuation and failure 
      • screw fixation of the graft bone block is within 20 mm of the popliteal artery
  • Single-bundle technique
    • approach
      • arthroscopic or open
    • technique
      • reconstruct the anterolateral bundle
      • tension at 90° of flexion
  • Double-bundle technique
    • approach
      • arthroscopic or open techniques may be utilized
    • technique
      • anterolateral bundle tensioned in 90° of flexion
      • posteromedial bundle tensioned in extension
    • pros & cons
      • biomechanical advantage with knee function in flexion and extension
      • clinical advantage has yet to be determined
      • may be advantageous to perform with combined PCL/PLC injuries for better rotational control as PLC reconstructions typically loosen over time
  • Postoperative care 
    • immobilize in extension early and protect against gravity
    • early motion should be in prone position
  • Rehabilitation
    • focus on quadriceps rehabilitation  
    • avoid resisted hamstring strengthening exercises (ex. hamstring curls) in early rehab
      • this is because the hamstrings create a posterior pull on the tibia which increases stress on the graft.
  • Popliteal artery injury   
    • at risk when drilling the tibial tunnel (increases with knee extension) 
    • lies just posterior to PCL insertion on the tibia, separated only by posterior capsule
  • Patellofemoral and medial sided pain/arthritis 
    • due to chronic PCL deficiency 

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