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Updated: May 31 2023

PCL Injury

Images
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https://upload.orthobullets.com/topic/3009/images/posterior sag sign_moved.jpg
https://upload.orthobullets.com/topic/3009/images/posterior drawer_moved.jpg
https://upload.orthobullets.com/topic/3009/images/pcl injury lateral stress views.jpg
https://upload.orthobullets.com/topic/3009/images/pcl grade iii intrasubstance tear sagittal mri.jpg
  • Summary
    • PCL injuries are traumatic knee injuries that may lead to posterior knee instability and often present in combination with other ipsilateral ligamentous knee injuries (i.e PLC, ACL).
    • Diagnosis can be suspected clinically with a traumatic knee effusion and increased laxity on a posterior drawer test but requires an MRI for confirmation.
    • Treatment can be nonoperative or operative depending on the severity of injury to the PCL, as well concomitant injuries to surrounding structures and ligaments in the knee.
  • Epidemiology
    • Incidence
      • 5-20% of all knee ligamentous injuries
  • Etiology
    • 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
  • Anatomy
    • PCL anatomy
      • origin
        • anterolateral medial femoral condyle
        • broad, crescent-shaped footprint
      • insertion
        • posterior tibial sulcus below the articular surface
      • 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
      • PCL injury classification
      • (based on posterior subluxation of tibia relative to femoral condyles with knee in 90° of flexion)
      • Grade I
      • partial tear
      • exam shows 1-5 mm posterior tibial translation
      • Tibia remains anterior to the femoral condyles
      • Grade II
      •  a complete isolate tear
      •  exam shows 6-10 mm posterior tibial translation
      •  complete injury in which the anterior tibia is flush with the femoral condyles
      • Grade III
      • a combined PCL + capsuloligamentous injury
      •  exam shows >10mm posterior tibial translation
      •  tibia is posterior to the femoral condyles and often indicates an associated ACL and/or PLC injury
  • Presentation
    • 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)
        • 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
        • 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
  • Imaging
    • 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
  • Treatment
    • 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
  • Rehabilitation
    • 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.
  • Complications
    • 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
  • 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
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