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How Commonly are Pedicle Screws Adjacent to the Great Vessels or Viscera? A Study of 2,295 Pedicle Screws: PAPER #38

Amaral, Terry D. MD; Wollowick, Adam L. MD; Kulkarni, Preethi M. MD; Thornhill, Beverly MD; Suggs, William MD; Sugarman, Etan P. MSIV; Horn, Jonathan J.; Sarwahi, Vishal MD

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Spine Journal Meeting Abstracts: 2011 - Volume - Issue - p 74
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Summary: Misplaced pedicle screws impinging upon blood vessels or viscera is a rare but formidable event and seems to be unrelated to patient or curve characteristics.

Introduction: The rate of pedicle screw misplacement is estimated to be 10%. Vascular or visceral injury can be catastrophic for the patient. As most misplacements are asymptomatic, they are frequently undetected. This study identified the rate of screw placement in proximity to vital structures using post‐operative CT scans.

Methods: Post‐operative low‐dose CT scans of 106 patients who underwent posterior spinal fusion for scoliosis were reviewed. Screws adjacent to, in contact with, impinging upon, or penetrating blood vessels, pleura, esophagus, diaphragm, or trachea were evaluated. 2229 screws were reviewed. Limited low‐dose CT scan in the prone position was performed when screw location was ill defined. Patient and curve characteristics were recorded for correlation.

Results: 45 screws (2.2%) in 27 patients (25%) were found to be of great concern. 36 were in proximity to aorta, 1 to left subclavian artery, 5 to esophagus, 3 to trachea, 2 to pleura, and 1 to diaphragm. Of the 36 screws in proximity to the aorta, 13 screws in 6 patients were impinging or distorting the aortic wall. 95% of misplaced screws were in the thoracic spine. 53.3% were lateral, 28.9% were anterolateral, and 17.8% were anterior. 55.5% were 35mm long, 37.7% were 30mm, and 6.6% were 25mm. 56% were in pedicles with normal morphology, and 75% were in curves between 40‐70 degrees.

Conclusion: Pedicle screws placed in close proximity to blood vessels or viscera are rare when compared to the total number of screws placed. However, a large number of patients (25%) had screws of concern. Most are in the thoracic spine, in curves between 40‐70 degrees, and are equally likely in normal and abnormal pedicles. However, the majority of misplacements are asymptomatic and thus are undetected.

Significance: Although only a small number of screws are of concern, they occurred in a large percentage of patients (25%). A single screw of concern in any patient can lead to significant consequences for the patient. Surgeons placing pedicle screws in deformed spines must be vigilant about proper placement. Post‐operative imaging beyond routine x‐rays may be needed to detect screws of concern even in asymptomatic patients.

© 2011 Lippincott Williams & Wilkins, Inc.