RESUMO
Posterior cervical spine fixation is a key component in achieving spinal arthrodesis for treating various cervical spine pathologies including neoplastic, inflammatory, traumatic and degenerative diseases. Historically, various wiring techniques had played major roles in posterior cervical spine fixation. Today, posterior cervical screw fixation is utilized by most spine surgeons instead of wiring for its superior biomechanical strength. A review of lateral mass, pedicle, intralaminar and transfacet screw fixation techniques in the subaxial cervical spine is presented in a detailed fashion. A comparison among different posterior cervical subaxial fixation techniques is also included. Although the safety of freehand techniques was demonstrated in the majority of the existing studies, real-time navigation is becoming increasingly utilized for cervical screw insertion, especially for cervical pedicle screws, where the freehand technique is technically demanding and may carry a higher risk of neurovascular injury. Several different posterior screw fixation techniques exist for the subaxial cervical spine with generally low complication rate. Spine surgeons should be familiar with these techniques and choose the optimal technique based on each patient's individual anatomy and surgical needs.
RESUMO
STUDY DESIGN: A narrative literature review. OBJECTIVES: To review the surgical techniques of posterior screw fixation in the subaxial cervical spine. METHODS: A broad literature review on the most common screw fixation techniques including lateral mass, pedicle, intralaminar and transfacet screws was performed on PubMed. The techniques and surgical nuances are summarized. RESULTS: The following techniques were described in detail and presented with illustrative figures, including (1) lateral mass screw insertion: by Roy-Camille, Louis, Magerl, Anderson, An, Riew techniques and also a modified technique for C7 lateral mass fixation; (2) pedicle screw fixation technique as described by Abumi and also a freehand technique description; (3) intralaminar screw fixation; and finally, (4) transfacet screw fixation, as described by Takayasu, DalCanto, Klekamp, and Miyanji. CONCLUSIONS: Many different techniques of subaxial screw fixation were described and are available. To know the nuances of each one allows surgeons to choose the best option for each patient, improving the success of the fixation and decrease complications.
RESUMO
Objetivos: Realizar un análisis morfométrico del atlas por tomografía computada, determinando los valores promedio, medianos, y de variabilidad de dicha vértebra para la correcta colocación de tornillos trans-masas laterales. Introducción: Existe una significativa variabilidad interpersonal en los aspectos morfológicos del atlas, y dada su proximidad a estructuras neurovasculares (arteria vertebral, médula cervical, raíz de C2), hacen mandatario un exhaustivo planeamiento prequirúrgico para la elección de la técnica de artrodesis, tipo de tornillos a utilizar, y su trayectoria. Material y métodos: Se realizó un estudio de diseño de tipo exploratorio, descriptivo, observacional, retrospectivo, transversal. Se revisaron 99 tomografías computadas de la columna cervical. Se midieron parámetros morfométicos y angulaciones desde un "punto de entrada" en la masa lateral de C1, que fueron llamados A, B, C, D, E, F, G y H. Las mediciones de los parámetros a estudiar fueron realizadas con el programa RadiAnt DICOM Viewer (64-bit) y posteriormente volcadas a una ficha de registro de datos. Discusión: La distribución según género fue de 34 varones y 65 mujeres. Se encontró una diferencia estadísticamente significativa no solo en lo referente al género (masculino vs femenino; parámetros A, B, C, D, F, G, H p-valor < 0,05) de los parámetros medidos, sino también según lateralidad (derecha vs izquierda; parámetros C, E, F, G p-valor < 0,05). La investigación propone además la generación de una base de datos con información morfométrica del atlas. Conclusión: Existe una diferencia estadísticamente significativa en las propiedades morfológicas del atlas, tanto en lo relativo al género (masculino vs femenino), como en la lateralidad (derecha vs izquierda). Es por ello que el presente estudio enfatiza en la importancia de la realización prequirúrgica de una tomografía computada de la columna cervical superior para garantizar una efectiva y segura instrumentación a éste nivel, según el largo, ancho y trayectoria de los tornillos a utilizar.
Objectives: To morphometrically analyze the atlas, using computed tomography, thereby defining mean, median and variability values of C1 for the correct placement of lateral mass screws. Introduction: Significant interpersonal variability exists among the various morphological characteristics of the atlas. Given the structure's close relationship to neurovascular structures like the vertebral arteries, cervical spinal cord, and cervical roots, exhaustive pre-surgical planning becomes mandatory. Such planning assists in the choice of arthrodesis technique, and the dimensions and trajectory of screws. Material and Methods: A retrospective, observational study was performed, for which the computed tomography (CT) scans of 99 cervical spines were reviewed. Morpho-metric parameters and angulations were measured from an "entry point" in the lateral mass at C1; these parameters were alphabetically labeled from A through H. The RadiAnt DICOM Viewer (64-bit) program was used to measure all parameters of interest, the values of which then were entered into a data collection file.Discussion: By gender, there were 34 men and 65 women. A statistically-significant difference was found between the two genders for all parameters except parameter E (all p-values < 0,05), and between the two sides (right vs. left) for parameters C, E, F, and G. Our results argue for the creation of a general database containing morphometric information on the atlas. Conclusion: Statistically-significant differences exist between men and women, and from right to left, among the morphometrical features of the atlas. This underscores the need for careful preoperative surgical planning, including the use of CT scanning to estimate optimum screw lengths and trajectories.