Morphological measurement of anterior cervical pedicle screw placement assisted by Mimics three-dimensional CT reconstruction

Abstract

BACKGROUND: The anterior transpedicular screw fixation system can achieve adequate decompression and strong fixation in a single anterior surgery. However, due to its unique anatomical structure, the risk of screw placement is relatively high. Previous domestic and international scholars have confirmed the feasibility of this approach through anatomical measurements, but there are some drawbacks such as relatively small sample sizes, difficulties in locating the pedicle axis, and limitations in measurement methods. OBJECTIVE: To perform morphological measurements of the adult cervical spine based on imaging to provide anatomical guidance for anterior transpedicular pedicle screw fixation. METHODS: 3D CT scan data of 50 adult cervical vertebrae were imported into the Mimics system for 3D reconstruction. Morphological data were measured, including pedicle axis distance, pedicle width, pedicle height, pedicle horizontal axial angle, pedicle sagittal angle, distance from the entry point in the transverse plane, distance to the entry point in the sagittal plane, axial vertebral length and axial pedicle length. RESULTS AND CONCLUSION: (1) Positioning of nail entry points: C3 and C4 were located on the opposite side of the median sagittal plane of the vertebral body, with distances from the median sagittal line of approximately 2.060 mm and 2.310 mm. C5 could be located on the same side of the median sagittal line as or opposite to the median sagittal line, with an average value of approximately 1.224 mm. C6-C7 were located on the same side of the body, with distances of 1.132 mm and 2.538 mm from the midline; the distance from the upper endplate increased gradually from C3 to C7, with average values ranging from 2.362 to 7.350 mm. (2) Direction of nail entry: the transverse angle increased gradually from C3 to C4 (46.32°-47.36°) and decreased from C5 to C7 (44.03° to 37.80°); the sagittal angle required caudal deviation for C3-C4 (95.75° and 100.93°) and cephalad deviation for C5-C7 (104.38°, 110.34°, and 104.86°). (3) There were no significant differences in entry point location and direction between genders or sides (P > 0.05). For screw selection, except for individual patients with cervical developmental abnormalities, for most subaxial cervical pedicle screws, it is safe and reliable to choose screws at least 30 mm long and 4.0 mm in diameter for males, and at least 28 mm long and 3.5 mm in diameter for females. (4) Morphological measurements confirmed that anterior transpedicular screw fixation of the subaxial cervical spine is feasible, but individualized principles should be followed to formulate personalized fixation plans.

1. Introduction

Anterior cervical decompression and fusion is a common treatment for cervical spine diseases, offering advantages such as shorter operative time and reduced surgical trauma and complications [1-3]. However, the biomechanical stability of traditional anterior cervical plate and screw fixation is not satisfactory, with issues such as insufficient pullout resistance and poor fatigue resistance [4-5]. To achieve both thorough anterior decompression and strong posterior fixation in a single procedure, KOLLER et al. [6-7] first proposed the concept of cervical anterior transpedicular screw (ATPS) fixation in 2008. Due to the unique anatomical structure of the pedicle, with the spinal cord medially, the vertebral artery laterally, and nerve roots passing above and below [8-10], the risk of screw placement is relatively high.

In response, many renowned scholars have systematically described the anterior transpedicular screw fixation technique and obtained anatomical data through measurements, confirming the feasibility and clinical application prospects of this approach [7,11-13]. However, current domestic anatomical studies on anterior cervical pedicle screw placement have limitations such as relatively small sample sizes and restricted measurement methods. To more precisely define the morphological parameters for anterior transpedicular screw fixation, this study utilized the interactive medical image control system Mimics software to perform individualized and quantitative analysis of screw placement based on 3D CT imaging of 50 patients. This approach enables more accurate morphological measurements and explores the morphological characteristics, thereby providing anatomical references for clinical practice.