Anatomical and Imaging Study on the Optimum Entry Point and Trajectory for Anterior Transpedicular Root Screw Placement into the Lower Cervical Spine

Abstract

Objective. To study the optimum entry point and trajectory for anterior transpedicular root screw (ATPRS) placement into the lower cervical spine (LCS), so as to provide a basis for clinical application. Methods. A retrospective analysis of cervical CT images of patients who underwent cervical CT examination in the Spinal Surgery of Ningbo No. 6 Hospital from January 2020 to August 2021 was conducted. The data were obtained and modeled. On the coronal plane, the vertebral body (VB) between the anterior midline of cervical vertebral segments C3-7 and the left P line (by drawing the line parallel to the anterior midline of the VB at the intersection of the anterior edge of the Luschka’s joint and the upper endplate) was equally divided into 9 zones (a-i). The ideal entry point and path of cervical ATPRS were designed and recorded. Additionally, 7 cadaveric specimens were selected, and the screw placement parameters were regenerated according to the above methods for screw placement. Results. Zone i of each segment, with the longest screw length, was the best area for screw placement. In all patients, the horizontal angles of vertebrae C3-7 in zones a, d, and g, zones b, e, and h, and zones c, f, and i showed a gradually decreasing trend. The sagittal angle range of C3-7 in all patients showed a gradually increasing trend in zones a-c, d-f, and g-i. The distance from the anterior midline of C3-7 to the P line increased in all patients, and the distance was longer in males than in females, with statistical significance. Pedicle screws were successfully inserted in all the 7 cadaveric specimens. Conclusions. ATPRS placement can be used for LCS internal fixation, and the precise screw placement parameters can be simulated by the software, which provides theoretical basis for its future clinical application.

Biomechanical study of anterior transpedicular root screw intervertebral fusion system of lower cervical spine: a finite element analysis

“…Once validated, the model can effectively accommodate various constraints, loading conditions, and material properties for different tests conducted by researchers ( Wang et al, 2023 ). Consequently, this analysis method has been widely utilized in cervical spine biomechanics research ( Lin et al, 2021 ; Zhang et al, 2022 ; Liang et al, 2022 ). In this study, we used cervical spine CT imaging data from a healthy adult male to rebuild the intact FE model of the lower cervical spine, and FE models of ACLP, ATPS, and ATPRS internal fixation methods were simultaneously established.…”

“…Constraints were applied to the four FE models to keep the lower endplate of C7 completely fixed and C3 unconstrained. Based on previous literature, an axial pressure of 75 N was applied to the upper surface of the C3 vertebra to mimic the weight of the head ( Zhang et al, 2022 ). A 1.0 Nm moment was loaded at the coupling point on the upper surface of the C3 vertebra to cause anterior flexion, posterior extension, lateral flexion, and axial rotational activity in the FE models ( Lee et al, 2016 ; Liang et al, 2022 ).…”

“…So far, there only have been several reports on the clinical application of ATPS ( Zhang et al, 2019 ; Pei et al, 2022 ). Consequently, we have undertaken enhancements to the ATPS technology, culminating in the proposal of the ATPRS technology ( Zhang et al, 2022 ). In the sagittal plane, the head end of ATPRS is located on the axis of the pedicle; in the horizontal plane, the head end of ATPRS is positioned at the junction of the pedicle axis and the posterior edge of the vertebral body.…”