An Evaluation of Image-Guided Technologies in the Placement of Anterior Thoracic Vertebral Body Screws in Spinal Trauma: A Cadaver Study

Abstract

Background: Image guidance provides additional anatomic information to the surgeon, which may allowmore accurate insertion of spinal implants. Imprecise placement of anterior thoracic screws places the spinalcord and paraspinal structures at risk for injury. Image guidance may afford a safety benefit to patients whenanterior thoracic screws are required in the setting of spinal stabilization after trauma.Objectives: To compare the accuracy of anterior thoracic screw placement using standard fluoroscopy,computer-assisted fluoroscopic image guidance, lso-C3D image guidance, and electromagnetic fluoroscopicimage guidance.Study Design: A surgical simulation study in human cadaver spine specimens.Methods: After an open thoracotomy approach, anterior thoracic screws were placed by experienced spinesurgeons using 4 different image-guided techniques in 4 human cadaver thoracic spines. Screws were placedin the 9th, 1Oth, and 11th thoracic vertebrae of each specimen. The specimens were then examined with thincutcomputed tomography (CT) scans, and with sagittal and coronal reconstructions. Measurements includedthe distance of the screw from the spinal canal, the angle of the screw path in relation to a perpendicular toa line that bisects the spinous process, and the angle of screw divergence from the superior endplate.Results: There was no evidence of sp inal canal penetrance with any of the image-guided techniques usedto place anterior thoracic vertebral body screws. Screws inserted with standard fluoroscopy tended to aimanterolaterally by 18°. The image-guidance systems allowed more accurateplacement of anterior thoracicscrews in the transverse plane compared with standard fluoroscopy. There was no statistically significantdifference in coronal plane screw angulation (angle of divergence with the superior endplate) between anyof the imaging methods.Conclusions: Spinal image-guidance systems may allow spine surgeons to place anteriorthoracic screws moreprecisely, particularly in the axial plane. The improved accuracy of spinal implant insertion could ultimately provide a benefit to patient safety, especially in the setting of malaligned vertebral bodies after trauma.