Pedicle screw fixation of the C7 vertebra using an anteroposterior fluoroscopic imaging technique

Abstract

Cervical pedicle screws have been reported to be biomechanically superior to lateral mass screws. However, placement of these implants is a technical challenge. The purpose of this investigation was to use an anatomic and a clinical study to evaluate a technique for placement of the pedicle screws in the C7 vertebra using fluoroscopic imaging in only the anteroposterior (A/P) plane. Ten adult cadaver C7 vertebrae were used to record the pedicle width, inclination and a suitable entry point for placement of pedicle screws. A prospective study of 28 patients undergoing posterior instrumentation of the cervical spine with C7 pedicle screw placement was also performed. A total of 55 C7 pedicle screws were placed using imaging only in the A/P plane with screw trajectory values obtained by the anatomic study. Radiographs and CT scans were performed post-operatively. The average posterior pedicle diameter of C7 vertebra was 9.5 ± 1.2 mm in this study. The average middle pedicle diameter was 7.1 mm and the average anterior pedicle diameter was 9.2 mm. The average transverse pedicle angle was 26.8 on the right and 27.3 on the left. CT scans were obtained on 20 of 28 patients which showed two asymptomatic cortical wall perforations. One screw penetrated the lateral wall of the pedicle and another displayed an anterior vertebral penetration. There were no medial wall perforations. The preliminary results suggest that this technique is safe and suitable for pedicle screw placement in the C7 vertebra.

Comparison of Three Different Options for C7 Posterior Vertebral Anchor in the Indian Population—Lateral Mass, Pedicle, and Lamina: A Computed Tomography-Based Morphometric Analysis

“…C7 fixation may be an inevitable component in posterior cervical or cervicothoracic stabilization [ 10 ]. Although lateral mass fixation is the gold standard for C3–C6 fixations, the C7 lateral mass has been considered less conducive for screw fixation.…”

Easy method to simplify “freehand” subaxial cervical pedicle screw insertion

“…[ 3 ] Pedicle screw fixation in the cervical spine due to three column stabilization provides significantly greater rigidity compared with lateral mass screw fixation,[ 4 5 6 7 ] this is most important in cases of poor bone quality. [ 4 ] Numerous biomechanical studies show the reliability of the SCPS fixation,[ 4 6 8 9 ] nevertheless many authors note high risk of neurovascular injury. [ 1 10 11 12 13 14 15 ] The wide variability of pedicle size in cervical region complicates the choice of standard bony landmarks, necessary to determine the optimal screw entry point.…”

Safety and efficacy of lateral mass screws at C7 in the treatment of cervical degenerative disease

“…C7 anatomy is different from other cervical vertebrae as it transitions to the thoracic spine. [ 2 ] Further, because C7 is often the most caudal point of fixation in multilevel constructs and is the site of highest stress concentration, optimal screw placement concerns are often focused on C7. In several biomechanical studies, PS have been shown to have superior pull-out strength in comparison with LMS at C7.…”