Feasibility study of free-hand technique for pedicle screw insertion at C7 without fluoroscopy-guidance

Abstract

Study Design: Retrospective interventional study. Purpose: To introduce a free-hand pedicle screw (PS) insertion technique without fluoroscopic guidance in the C7 vertebra and evaluate the procedure's feasibility and radiologic outcomes. Overview of Literature: Although PS insertion at C7 has been recognized as a critical procedure in posterior cervical fusion surgery, conventional techniques for C7 PS have several limitations. Methods: Thirty two patients (64 screws) who underwent PS insertion in C7 with the novel technique were included in this study. Postoperative clinical and radiological outcomes were evaluated. Special attention was paid to the presence of any problems in the screw position including cortical breaches of the PS and encroachment of the PS into the spinal canal or the vertebral foramen. This novel technique for PS insertion in C7 without fluoroscopy guidance had three key elements. First, the ideal PS entry point was chosen near the C6-7 facet joint using preoperative images. Second, the convergent angle distance was measured at axial computed tomography (CT) imaging, which defined the distance between the tip of C7 spinous process and the extended line passing through the pedicle axis from the ideal entry point. Third, the cranial-caudal angle distance was measured in sagittal CT images, which defined the distance between the tip of the C7 spinous process and the extended line passing through the pedicle axis. Results: Cortical breach on postoperative CT images was observed in three screws. All violated only the lateral wall of the affected pedicle. The breached screws occurred in the initial five cases. Postoperative neurologic deterioration was not observed in any patient, regardless of cortical breaching. Conclusions: The novel technique successfully allows for C7 PS to be placed and is associated with a low rate of cortical breach.