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. 2020 May 15;45(10):E576-E581.
doi: 10.1097/BRS.0000000000003344.

The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility

Vishal Sarwahi  1   2 , Jesse Galina  1   2 , Stephen Wendolowski  1   2 , Beverly Thornhill  1   2 , Aaron Atlas  1   2 , Rachel Gecelter  1   2 , Sayyida Hasan  1   2 , Yungtai Lo  2   3 , Terry D Amaral  1   2
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The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility

Vishal Sarwahi et al. Spine (Phila Pa 1976). .

Abstract

Study design: Retrospective chart review.

Objective: To determine if obtaining a prone computed tomography (CT)-scan can better delineate a questionable screw-aorta relationship.

Summary of background data: Pedicle screw misplacement rate is reported between 6% and 15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention.

Methods: One hundred eleven spinal deformity patients who underwent Posterior spinal fusion from 2004 to 2009 were evaluated. Patients with concerning screw-aorta relationship underwent additional prone CT scan. Mobility of the aorta was determined and distance was compared using prone and supine CT scans.

Results: Two thousand two hundred ninety five screws were reviewed, 36 screws in 18 patients were in proximity to the aorta. Fourteen screws (nine patients) appeared to be impinging the aorta. On prone CT, 13 out of the 14 instances the aorta moved away from the screw. The average distance at the screw level was 13.6 ± 4.8 mm in supine position and 8.9 ± 5.4 mm in prone position (P = 0.001). In one instance the relationship was unchanged on prone CT. No screw was noted to violate the lumen or distort the aorta.

Conclusion: Supine CT scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization.

Level of evidence: 3.

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References

    1. Gaines RW Jr. The use of pedicle-screw internal fixation for the operative treatment of spinal disorders. JBJS 2000; 82:1458–1476.
    1. Kim YJ, Lenke LG, Cho SK, et al. Comparative analysis of pedicle screw versus hook instrumentation in posterior spinal fusion of adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 2004; 29:2040–2048.
    1. Suk SI, Lee SM, Chung ER, et al. Selective thoracic fusion with segmental pedicle screw fixation in the treatment of thoracic idiopathic scoliosis: more than 5-year follow-up. Spine (Phila Pa 1976) 2005; 30:1602–1609.
    1. Hicks JM, Singla A, Shen FH, et al. Complications of pedicle screw fixation in scoliosis surgery: a systematic review. Spine (Phila Pa 1976) 2010; 35:E465–E470.
    1. Sarwahi V, Wendolowski SF, Gecelter RC, et al. Are we underestimating the significance of pedicle screw misplacement? Spine (Phila Pa 1976) 2016; 41:E548–E555.

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