Popliteal arteriovenous malformation

MR angiogram of knee was correlated with plain CT and targeted Doppler interrogation.

A tuft of arteriovenous malformation is seen in popliteal fossa with direct arterial feeders from popliteal artery as well as epiphyseal and metaphyseal arteries of distal femur. Venous drainage is through direct and indirect tributaries into popliteal vein. The malformation 'lights up' as early as the second phase of angiogram. The largest nidus is just popliteal vessels measuring 4.0 x 2.8 cm in maximum dimensions. The second largest is seen abutting posterior metaphyseal cortical margin measuring 2.2 x 1.5 cm in maximum dimensions. Serpentine dilated sac abuts posterior distal femoral metaphyseal cortex with areas of chronic extrinsic pressure imprints causing cortical  thinning and at certain sites cortical break. There is erosion and loss of approximately 50 % of superior half of lateral femoral condyle.

Menisci
Medial meniscus: grade 2 degeneration posterior horn outer half.
Lateral meniscus: grade 2 degeneration anterior root.

Ligaments
Cruciate ligaments: intact with grade 2 anterior ruciate ligament degeneration. Grade 1 injury of posteromedial bundle femoral attachment of posterior cruciate ligament.
Medial collateral ligament: superficial and deep components intact. No periligamentous edema.
Lateral collateral ligament: intact
Posterolateral corner structures: intact

Extensor mechanism
The distal quadriceps and patellar tendons are intact. The patella is normally positioned within the femoral groove. There is no retinacular disruption.

Fluid
Multiple posterior distal femur trapped synovial cysts. Moderate suprapatellar effusion with synovial thickening. No popliteal cyst.

Osseous and articular structures
Patellofemoral compartment: grade III lateral patellofemoral chondromalacia.
Medial compartment: grade 1 hyaline cartilage disease. Reduced joint space.
Lateral compartment: grade 1 hyaline cartilage disease. Reduced joint space.

Conclusion

• Tuft of high flow arteriovascular malformation with multiple niduses in  popliteal fossa, with arterial feeders from popliteal artery and distal femoral epimetaphyseal arteries. Venous drainage through multiple tribuatries into popliteal vein. Secondary posterior distal femur bony erosions and cortical break, approximately 50% superior lateral femoral condyle bone loss.
   

• Knee internal derangements

  • Grade 2 degenerate  posterior horn medial meniscus.

  • Grade 2 degenerate anterior root lateral meniscus.

  • Grade 2 ACL degeneration.

  • Grade 1 injury posteromedial PCL bundle.

  • Grade 3 lateral patellofemoral chondromalacia.

  • Moderate suprapatellar chronic effusion with synovial hypertrophy.

CT correlation reveals the chronicity of the lesion, the pressure changes that led to bony erosions in distal femur. 

Doppler study identifies the yin-yang sign with clear arterial feeder and venous tributary off the nidus.