Laboratory and Imaging Studies
Laboratory studies
Perform laboratory studies as indicated per patient age.
Imaging studies
Radiographs
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Acute injuries
Routine radiographs usually are negative in acute injuries.
Bony avulsions may be evident on lateral radiographs.
New radiological view: Axial radiograph as described by Puddu et al. Patient is supine with knees flexed to 70°, feet are plantigraded in moderate plantar flexion, and the tibia is in neutral rotation. With patient holding cassette, the radiographic beam is directed distal to proximal and parallel to the longitudinal axis of the patella. The length of the perpendicular line between the anterior tibial profile and the femoral groove is measured. If the side-to-side difference is >3 mm, posterior laxity is indicated.
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Chronic lesions
Weight-bearing anteroposterior (AP) or Rosenberg view (posteroanterior [PA] with knees flexed) may demonstrate early medial joint arthrosis.
Tangential patellofemoral view (Laurin/Merchant view) may demonstrate patellofemoral arthrosis.
Long-film AP weight-bearing views are essential for preoperative alignment.
Magnetic resonance imaging (MRI)
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If physical examination reveals multiple injured ligaments, or if degree of injury is in question, an MRI may be justified.
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MRI helps identify and confirm the location of the lesion; in addition, occult osteochondral lesion/fractures and meniscal lesions may be identified. MRI of acute injury is more accurate than for chronic injury, as the ligament may appear healed but be functionally deficient. [8] (See the images below.)
Other Tests and Procedures
Other tests
Occasionally, a patient with a posterior knee injury may present with calf pain and signs of an impending compartment syndrome, possibly due to soft tissue injury or signs of an occult vascular injury. The calf symptoms may be more pronounced than the knee symptoms. Compartment pressures need to be measured, and vascular surgery consultation must be considered for an arteriogram.
Procedures
Perform an arteriogram in patients with suspected vascular injury, such as an injury that might be seen with knee dislocation.
Arthroscopic posteromedial drive-through test can reveal PCL rupture (grade III PCL instability). The test is positive if it is easy to pass the arthroscope between the medial femoral condyle and the PCL. This test had an overall accuracy of 97.6%. [9]
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A normal lateral radiograph of a knee. In a normal knee, a line drawn along the posterior femoral condyle will not intersect the posterior tibial condyle.
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A lateral radiograph of a knee with a posterior cruciate ligament injury. Note that the same line as in the above image will bisect the posterior tibial condyle due to a posterior sag and an incompetent posterior cruciate ligament.
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The posterior tibial sag sign. The photo on the left demonstrates the clinical finding of the posterior tibial sag sign. A line drawn parallel to the patella accentuates the posterior tibial sag. The photo on the right demonstrates the quadriceps active drawer test described by Daniels. With the knee in 70-90° of flexion, the extensor mechanism is contracted, pulling the tibia anteriorly into a reduced position.
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A close-up view of a posterior tibial sag with an incompetent posterior cruciate ligament.
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This MRI of the knee shows a torn posterior cruciate ligament.
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This MRI (coronal section) shows a posterior cruciate ligament tear.
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This transverse MRI shows edema to the torn posterior cruciate ligament.
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A view of the broad origin of the posterior cruciate ligament (PCL) on the medial femoral condyle of a left knee. The anterior cruciate ligament has been removed for surgical reconstruction.
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An additional view of the posterior cruciate ligament broad origin and insertion in a knee pending anterior cruciate ligament reconstruction.
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A right knee pending posterior cruciate ligament (PCL) reconstruction. A minimal notchplasty is completed. Two guide pins are advanced into the medial femoral condyle for tunnel placement to reconstruct the 2 bundles of the PCL.
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The 2 tunnels are created by reaming from outside in; 8- to 9-mm tunnels are made depending on patient size and the graft that will be used.
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Two red Robinson catheters are advanced through the femoral tunnels.
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The catheters have premade holes, which are used for suture retrieval.
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The catheters are advanced and threaded out the posterior knee. In this case, a posterior tibial onlay graft from an Achilles tendon allograft is used. The 2 bundles are secured to the catheters and advanced into the joint through the tunnels.
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The 2 Achilles tendon bundles are secured with a baseball whipstitch, are threaded through the catheter holes, and are advanced into the femoral condyle tunnels.
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Additional view of the placement and advancement of the Achilles allograft.
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Completion and seating of the femoral allograft reconstruction. The 2 bundles are secured or stabilized by suturing over a post and washer. Note the reestablishment of the broad surface area for the reconstructed posterior cruciate ligament origin.
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Completion of the tibial onlay, 2-bundle Achilles tendon allograft/posterior cruciate ligament (PCL) reconstruction. The bony calcaneus remnant is secured to the posterior tibia with 1 or 2 interfragmentary compression screws into a trough into the posterior tibia at the level of the PCL insertion. Care is taken to not penetrate the anterior tibial cortex with these screws. Note the intact original anterior cruciate ligament.
