Reliability of three-dimensional fluoroscopy for detecting pedicle screw violations in the thoracic and lumbar spine.
OBJECTIVE
Thoracic and lumbar pedicle screws have become popular because of their biomechanical superiority over other methods of spinal fixation. However, the safety and efficacy of transpedicular screws depend on their proper placement. Recent advances in imaging have resulted in the ability to acquire three-dimensional (3-D) axial images of the spine during surgery, and this study was undertaken to assess the reliability of this technology to detect pedicle violations.


METHODS
Pedicle screws were placed in six human cadaver spines from T1 to S1 using standard techniques. Intentional pedicle violations were created in 74 of 216 pedicles, and violations were graded on a four-point scale (range, 0-3). Radiographic images were then obtained using a conventional spiral computed tomographic scanner and the Siremobil Iso-C 3D (Siemens Medical Solutions, Erlangen, Germany) 3-D fluoroscopy unit. An independent neuroradiologist then graded pedicle violations as ascertained by the two imaging modalities.


RESULTS
Using direct inspection of the pedicles as the "gold standard," the overall sensitivity and specificity for detecting pedicle violations were 0.716 and 0.789, respectively, with 3-D fluoroscopy. The overall sensitivity and specificity for detecting pedicle violations were 0.608 and 0.937, respectively, with conventional computed tomography. All Grade 2 pedicle violations were detected in the thoracic spine by both modalities, and all Grade 3 violations were detected by both modalities.


CONCLUSIONS
Axial images obtained with 3-D fluoroscopy demonstrate a higher sensitivity but lower specificity than conventional computed tomographic scanning for assessing pedicle violations. By providing real-time intraoperative imaging, 3-D fluoroscopy may enhance the safety of thoracic transpedicular instrumentation.
Wang
Michael Y
MY
Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA. myw@usc.edu
Kim
K Anthony
KA
Liu
Charles Y
CY
Kim
Paul
P
Apuzzo
Michael L J
ML
D001863:Bone Screws; D005471:Fluoroscopy / Q000295:instrumentation*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed