Abstract
ObjectThere is a high probability of iatrogenic perforation of the vertebral pedicle wall during the application of subaxial cervical pedicle screw (CPS). The goal of this study was to evaluate the accuracy of CPS insertion at C3-C7 in vitro using novel calipers based on the gravity line.MethodsNine cadaveric cervical spines underwent computed tomography scanning and preoperative design. A lateral fluoroscopic view was taken to measure the intra-operative sagittal angle by C-arm with hanging cross structured K-wires. By referring to the gravity line, caliper A was used to locate the entry point, while caliper B was employed to guide the screw insertion. Postoperative CT scans were performed to assess the accuracy of the screw placements, according to the Neo classification.ResultsOverall, 78 (88.6%) of the 88 pedicle screw placements were classified as grade 0 (correct position), 4 (4.5%) were grade 1 (non-critical perforation), 4 (4.5%) were grade 2 (critical perforation), and 2 (2.3%) were grade 3 (critical perforation).ConclusionsUsing our novel calipers and referring to the gravity line was helpful for locating and guiding individual cervical pedicle screw insertions.
Highlights
78 (88.6%) of the 88 pedicle screw placements were classified as grade 0, 4 (4.5%) were grade 1, 4 (4.5%) were grade 2, and 2 (2.3%) were grade 3
Since Abumi et al first reported the results of cervical pedicle screw (CPS) fixation for traumatic lesion of the subaxial cervical spine, several studies have been performed indicating its superior biomechanical stability over lateral mass screws[1,2,3]
The ideal placement of the CPS requires an accurate entry point, with an appropriate trajectory angle and screw size, incorrect CPS placement can sometimes result in lethal perforation in the C3–7 region[4,5,6]
Summary
Since Abumi et al first reported the results of cervical pedicle screw (CPS) fixation for traumatic lesion of the subaxial cervical spine, several studies have been performed indicating its superior biomechanical stability over lateral mass screws[1,2,3]. The ideal placement of the CPS requires an accurate entry point, with an appropriate trajectory angle and screw size, incorrect CPS placement can sometimes result in lethal perforation in the C3–7 region[4,5,6]. While the transverse angle of the pedicle is easy to obtain in preoperative computed tomography (CT), the real-time, intra-operative sagittal angle is harder to acquire. This is because the superior or inferior vertebral endplate, which is chosen as the reference line in preoperative design[7, 10,11,12], is useless during the operation. It’s meaningful to design an assistant tool to achieve the ideal screw insertion at ideal angles by means of C-arm
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