Utilization of MRI Venography in the Determination of Pelvic and Lower Extremity Thromboembolism After Anterior Spinal Fusion Procedures

Lutheran General Hospital, Chicago, Illinois, USA

PURPOSE:
The evaluation of postoperative spinal patients for venous thromboembolism of the pelvis and lower extremities is a difficult task. Venous duplex scanning is not sensitive in evaluating clots proximal to the inguinal ligament. Because of two episodes of fatal thromboembolism associated with anterior spinal surgery, it was decided to initiate a pilot study utilizing a new technology of MRI venography in patients undergoing anterior spinal surgery of the thoracolumbar spine.

METHODS:
24 patients who have undergone anterior spinal fusion procedures with and without instrumentation underwent MRI venography and Duplex venous scanning between post-op day 3 to 5. The studies were read independently by 2 experienced MR radiologists.

RESULTS:
The results of MRI venography were compared with Duplex scanning. Correlation of radiographic readings was excellent for MRI venography. The presence of titanium spinal instrumentation, and titanium mesh fusion cages did not significantly degrade the venography images. A single positive MRI venogram revealed a large floating clot in the vena cava of a 19 yo female who had undergone anterior spinal fusion. Her Venous Duplex scan was negative at that time and on subsequent evaluations. She underwent emergent caval filter insertion, with venography confirming the diagnosis. Retroperitoneal hematomas were identified in 2 patients, in one case the left common iliac vein was compressed, but thromboembolism did not occur.

CONCLUSION:
MRI venography is a viable option in the postoperative evaluation/surveillance for vena caval, pelvic, and femoral vein thromboembolism in patients who have undergone anterior spinal fusion with or without spinal instrumentation.