PCL Reconstruction

• 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 

Anatomy:

• 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:

• 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

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 0° 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