Morphometric trajectory analysis for the C2 crossing laminar screw technique

Abstract

This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis has been performed to confirm the accuracy of screw trajectory using this technique. In this study, morphometric analysis was performed on 100 Korean C2 three-dimensional reconstruction CT images. The reconstructive C2 vertebrae from the post-edge of the spinal canal to the spinal process were divided into several zones, 1 mm each. Each zone was chosen as the entry point to imitate a crossing laminar screw (3.5 mm diameter) placement. In each 1-mm zoned trajectory, the screw pass ratio (PR), safe screw angle range (SAR) and maximum screw length (MSL) were measured and compared with the data from the other zoned trajectories. The zone '5-6 mm posterior to the post-edge of the spinal canal' was found to be a more feasible and safer entry point for guiding a crossing laminar screw placement than the other zones because this zone could provide a trajectory with maximal PR (85%), SAR (9.57 ± 4.368) and a larger MSL (21.74 ± 2.44 mm) than the other areas. The recommended safe screw angle in the axial plane is 49.68 ± 4.94 to 59.19 ± 4.708. However, the screw angle can vary considerably according to the individual variance. A preoperative evaluation of the screw trajectory is essential for safe screw placement using this technique.

The options of C2 fixation for os odontoideum: a radiographic study for the C2 pedicle and lamina anatomy

“…The data from general population may not apply to patients with OO. In addition, the use of C2 laminar screws in atlantoaxial fixation in attempt to reduce the risk for the vertebral artery (VA), was first reported by Wright et al [36] in 2004 and since became popular [18,19,38]. For OO patients, however, a couple of questions arise: can C2 pedicle screw be safely placed in every OO patient?…”

Задняя Фиксация Краниоцервикального Перехода С Использованием Винтовых Конструкций

“…после фиксации C 1 -C 2 по Harms: ротация в шейном отделе сочетается с флексионным компонентом (движения происходят за счет субаксиальных сегментов) ХИРУРГИЯ ПОЗВОНОЧНИКА Повреждения позвоночника 2/2014 (С. [42][43][44][45][46][47][48] А.В. Губин и др.…”

“…Траектория введения соответствует 50° в аксиальной плоскости. При этом оптимальная длина винта составляет 20-22 мм [42]. Данных о повреждениях невральных структур и позвоночных артерий при трансламинарном способе введения винтов в С 2 в литературе обнаружить не удалось.…”

Methods of Segmental Screw Fixation of Axis: A Cadaveric and Surgical Study

“…The screws can be inserted without breaching into spinal canal if the angle of insertion is ≥50° laterally. The reported maximum safe length of translaminar screws ranged from 21mm to 28mm, 21,23,25 which is slightly shorter than the transpedicular screws but significantly longer than trans pars screws. However, the recent radiological and cadaveric studies reported that the width of C2 lamina was <5mm in 15-29% of cases.…”