Establishment and Finite Element Analysis of a Three‐dimensional Dynamic Model of Upper Cervical Spine Instability

Abstract

Objectives To establish a dynamic three‐dimensional (3D) model of upper cervical spine instability and to analyze its biomechanical characteristics. Methods A 3D geometrical model was established after CT scanning of the upper cervical spine specimen. The ligament of the specimen was fatigued to establish the upper cervical spine‐instability model. A 100‐N preloaded stress was applied to the upper surface of the occipital bone, and then a 1.5‐Nm moment was applied in the occipital‐sagittal direction to simulate upper cervical spine flexion and extension. Subsequently, the 3D dynamic model was established based on trajectory data that were measured using a motion‐capture system. The stress on the main ligament and the relative motion angle of the joint were analyzed. Results The shape of the model grid was regular and the total number of its units was 627 000. After finite‐element analysis was conducted, results of the ligament stress and relative movement angle were obtained. After the upper cervical spine instability, the pressure of the alar ligament during the upper cervical spine extension was increased from 2.85 to 8.12 MPa. The pressure of the flavum ligament was increased during the upper‐cervical spine flexion, from 0.90 to 1.21 MPa. The pressure of the odontoid ligament was reduced during the upper cervical spine flexion and extension, from 10.46 to 6.67 MPa and 25.66 to 16.35 MPa, respectively. The pressure of the anterior longitudinal ligament and cruciate ligament was increased to a certain degree during upper cervical spine flexion and extension. The pressure of the anterior longitudinal ligament was increased during flexion and extension, from 7.70 to 10.10 MPa and 10.45 to 13.75 MPa, respectively. The pressure of the cruciate ligament was increased during flexion and extension, from 2.29 to 4.34 MPa and 2.32 to 4.40 MPa, respectively. In addition, after upper cervical spine instability, the articular‐surface relative‐movement angle of the atlanto‐occipital joint and atlanto‐axial joint had also changed. During upper cervical spine flexion, the angle of the atlanto‐occipital joint was increased from 3.49° to 5.51°, and the angle of the atlanto‐axial joint was increased from 8.84° to 13.70°. During upper cervical spine extension, the angle of the atlanto‐occipital joint was increased from 11.16° to 12.96°, and the angle of the atlanto‐axial joint was increased from 14.20° to 17.20°. Therefore, the movement angle of the atlanto‐axial joint was most obvious after induction of instability. Conclusion The 3D dynamic finite‐element model of the upper cervical spine can be used to analyze and summarize the relationship between the change of ligament stress and the degree of instability in cervical instability. Frequent or prolonged flexion activities are more likely to lead to instability of the upper cervical spine.

Cervical spine fracture prediction by simple plain X-ray in ankylosing spondylitis patients after low-energy trauma

“…A recent in vivo study showed that the exion-extension of C1-2 was 13.7 ± 4.2°, accounting for 14.5% of the overall exion-extension ROM; the lateral bending neck motion of C1-2 was 7.6 ± 2.7°, accounting for 13.2% of the overall lateral bending ROM; and the axial torsion neck motion of C1-2 was 72.9 ± 7.6°, accounting for 73.2% of the overall rotation ROM [22]. Previous investigations also achieved similar results [23,24,25]. Once the motion of C1-2 joint is restricted by the anterior continuous bony bridge, the bearing force capacity from the skull and the neck is in turn reduced, which further increases the risk of cervical fracture.…”

[Retracted] Clinical Efficacy and Safety of “Three‐Dimensional Balanced Manipulation” in the Treatment of Cervical Spondylotic Radiculopathy by Finite Element Analysis

“…It can provide information about stress distribution, deformation, and strain on any part of the cervical vertebrae during simulated manipulations, containing flexion, extension, and torsion [ 8 ]. Recently, different finite element models (FEM) of the cervical spine were constructed to investigate the biomechanics of the cervical spine or intervertebral disc [ 9 – 11 ]. However, few studies have established a FEM based on CSR, and few studies have performed biomechanical analysis of stress distribution, deformation of the model when imitating manipulation therapy.…”

Biomechanical Analysis of a Novel 3D Printing Cervical Spine Prosthesis : A Finite Element Study

“…Experimental biomechanics and theoretical biomechanics are two of the most common spinal biomechanics research methods. Compared with experimental biomechanics, theoretical biomechanics has its unique advantages: it can not only avoid high experimental costs and limited material sources, but also realize the prediction of the internal stressstrain eld of the spine [25][26]. As a theoretical biomechanical research method, FE analysis has been used for many years in the research of spinal mechanics [27][28].…”