Abstract: BACKGROUND: Among the pathogenic factors of cervical spondylosis, herniation of the intervertebral disc, dislocation of the facet joint and the stenosis of the intervertebral foramen are important factors leading to symptoms in patients. Moreover, inappropriate manipulation may aggravate the possibility of cervical disc rupture, leading to exacerbation of symptoms in patients.  
OBJECTIVE: To compare the effect between sagittal cervical manipulation and traditional cervical rotation manipulation on the area of the intervertebral disc, facet joint and intervertebral foramen at the operative segment by the finite element analysis.
METHODS: The neck CT data of a male volunteer with a normal neck were selected and imported into Mimics 17.0 three-dimensional reconstruction software. Geo-magic Studio 12.0, Solidworks 2017 and Ansys Workbench 17.0 software were used for the construction of the finite element model of cervical vertebrae (C3-6) including intervertebral disc and articular cartilage. The lower end plate of the C5 vertebral body was fixed. A uniformly distributed vertical downward 50 N load was applied on the upper surface of the upper vertebral body (C3). The stress, deformation and deformation direction of the C4-5 intervertebral disc, joint capsule stress, the displacement of facet joints and the area of bilateral intervertebral foramen were compared between sagittal cervical manipulation and traditional rotation reduction.  
RESULTS AND CONCLUSION: (1) When using the rotation technique, the maximum normal equivalent stress (von Mises stress) of the C4-5 disc was 8.06 MPa; the total deformation was 1.05 mm, and the fiber ring expanded to the left and outside. When using the sagittal tip lifting technique, the maximum normal equivalent stress (von Mises stress) of the C4-5 disc was 2.60 MPa; the total deformation was 0.90 mm, and the fiber ring expanded to the left and back. Compared with the rotation technique, the pressure of the cervical manipulation technique on the disc was less (about 32.3% of the rotation technique), and the deformation degree of the disc was also light (about 85.7% of the rotation technique). (2) When the rotation technique was used, the maximum stresses of the left and right articular capsule ligaments were 0.37 MPa and 1.69 MPa, respectively. The overall displacement of the facet joint was 2.21 mm. The area of the right intervertebral foramen decreased by about 3.8% and the area of the left intervertebral foramen increased by about 0.9%. When the sagittal end lifting manipulation was performed, the maximum stresses of the left and right articular capsule ligaments were 0.27 MPa and 1.70 MPa, respectively; the overall displacement of the facet joint was 1.63 mm; the area of the right intervertebral foramen increased by about 2.6%, and the area of the left intervertebral foramen decreased by about 0.9%. Compared with rotation manipulation, sagittal end lifting manipulation had fewer changes in the displacement of facet joint, joint capsule stress and intervertebral foramen area, so it was safer to operate. (3) In conclusion, compared with cervical rotation manipulation, sagittal end lifting manipulation has fewer changes in facet joint displacement, intervertebral disc stress/deformation degree, joint capsule stress, and foraminal area. In clinical practice, more appropriate manipulation should be selected based on biomechanical results after an accurate assessment of patients’ conditions.

Key words: cervical spondylopathy, sagittal cervical manipulation, traditional rotation reduction, three-dimensional finite element analysis, biomechanics